The relationship between physical fitness and competitive performance of Taekwondo athletes.

The competition and physical fitness test results of the 2020 National Taekwondo Championship Series were analyzed using curve fitting, linear regression, and other statistical methods. As far as we know, it is the first Taekwondo competition that uses physical fitness test (PFT) scores as the 8-in-4 selection criteria. The results show that the probability of the final total score of the series of championships entering the top 8 or top 3 is exponentially related to PFT results. It finds that athletes with better PFT scores are more likely to enter the quarterfinals. Among athletes entering the semifinals, the athlete with the best physical fitness has the greatest probability of winning the championship. The difference in physical fitness between athletes is mainly reflected in the 30-meter sprint. Overall, the competitive performance of professional Taekwondo athletes is significantly positively correlated with their physical fitness, especially for female Taekwondo athletes. Through the results obtained, it is concluded that Taekwondo athletes need to strengthen physical training, specifically enhancing the explosive power.

1. Introduction

Taekwondo originated in the Korean peninsula, which is famous for its flexible kicking techniques, and has been an Olympic combat discipline since 2000. In order to guide the training and competition more scientifically, reasons affecting the achievements of Taekwondo athletes have been studied extensively during the past few decades [1-5]. In general, performance in taekwondo is considered to be determined by a competitor’s technical, tactical, psychological, physical and physiological characteristics [1, 2].

Since the establishment of the World Taekwondo Federation (WTF) in 1973, the competition rules of Taekwondo have been revised more than 40 times [6]. In competitions conducted according to the pre-2015 rules, Taekwondo athletes did not generally apply difficult technical approaches, but preferred to use secure frontal skills to win the game [7], which is why the roundhouse kick was the most popular means of scoring [8]. However, following the changes in competition rules, Taekwondo competition tactics now have offensive tactics as the main approach and counter-attack tactics as the secondary approach [9]. As an important foundation of athletes’ competitive ability, physical fitness has also become increasingly prominent with the rule changes [10, 11].

In terms of physiological characteristics, it has been found that elite taekwondo athletes tend to possess low levels of body fat [12, 13], moderate to high levels of cardio-respiratory fitness [14] and high levels of both aerobic and anaerobic physical fitness [15], while muscle strength is often not a key role [16]. In terms of specific physical fitness characteristics, successful taekwondo athletes were found to possess significantly higher maximum running speed [12], better performance on 30m run, counter movement jump, moving sideways and walking backwards [17]. Additionally, research on the physical fitness test (PFT) of junior taekwondo athletes revealed that the power of lower extremities, strength and endurance are of great importance to the sports result [4, 18]. However, the aforementioned studies are limited by the fact that the PFTs performed were all conducted during training, because there is a big difference between training and competition modes for athletes’ psychological and physical conditions [15, 19, 20]. Therefore, further study on the relationship between PFT and athletes’ competition performance is still required.

Being aware of the important role of physical fitness for athletes’ competitive performance, the General Administration of Sport of China issued the “Notice on Further Strengthening Basic Physical Training and Complementary Physical Ability” (hereinafter “the Notice”) on February 24, 2020, which stipulates the competition system of combining physical fitness test with competition results. After that, the 2020 National Taekwondo Championship Series (NTCS) held in Wuxi, Jiangsu Province became the first taekwondo competition with PFT added to the rules, which also provided valuable data for the study of the relationship between athletes’ competition performance and PFT.

The main aim of this paper is to study the relationship between PFT results and taekwondo athletes’ competitive performance by analyzing the results of four competitions in the 2020 NTCS. As a supplement to the research on physiological indicators and PFT in training, this research hopes to use empirical research to provide a more macroscopic view of the role of physical fitness in Taekwondo competitions.

2. Materials and methods

The 2020 NTCS contained four competitions, two PFTs and a scoring system. The first and second competitions were held from September 22nd to 25th and September 27th to 30th, respectively. Prior to this, the first PFT (PFT1) was conducted from September 19th to 20th. The second PFT (PFT2), the third competition and the championship final (hereafter referred as the fourth competition) were held during October 15th to October 28th. Only athletes who have taken the PFT1 can participate in the first and second competitions, only athletes who have taken the PFT2 can participate in the third and fourth competitions.

A total of 638 professional Taekwondo athletes (393 males and 245 females) participated in the NTCS, all of whom were senior athletes from provincial teams in all provinces of China. All the athletes were required to compete in all four competitions and two PFTs. However, actually the number of athletes in each competition may vary slightly due to injuries or other reasons, e.g., school exams and unplanned restitution, etc. After each competition athletes were awarded points according to their competition ranking and the total number of points from the four competitions determines the final ranking of the athletes in the 2020 NTCS. The scoring rule of the NTCS was listed in . In summary, this could be calculated with the following formula: , where S represents points, M is determined by the competition ranking and bracket means rounding function.

The competition rules adopted for the NTCS is "World Taekwondo Competition Rules" (in force as of May 15, 2019) [21]. A three-round total points system was carried out for each match, each round is 2 minutes, and there is a 1-minute break between rounds. The PFT used in NTCS is similar to the German motor test [22], the US Army Air Forces PFT [23], the physical fitness scoring system for naval service personnel [24] and the national student fitness test in China [25]. Specifically, the 2020 NTCS PFT included five items, namely: weight-bearing squat, abdominal muscle endurance, back muscle endurance, 30-meter run and 3000-meter run. This battery of tests can be considered as an indicator stand for various aspects of an athlete’s athletic ability, including agility, explosive power, strength, aerobic capacity and anaerobic capacity, which has been viewed as a multidimensional structure that reflects motor performance ability [26]. The grading standard is given in .

Weight-bearing squat is used to test the strength of the quadriceps, gluteus maximus and other lower limb muscles [27]. The evaluation standard of squat strength is the ratio of the maximum squat weight to the body weight. Athletes are required to stand with feet slightly wider than shoulders, and toes can be rotated 15–30 degrees externally, squat until the front of the thigh reaches or below the horizontal line, and then squat up. Each athlete will test 3 times and take the highest weight. To test the endurance of the abdominal muscles, the test subject lies supine on a jump box with the torso suspended [28], the anterior superior iliac spine on the edge of the box, the arms crossed over the chest and the lower legs held in place by a belt, keeping the body in one plane and recording the longest time the athlete can hold on. The test method of back muscle endurance is the same as abdominal muscle endurance, except that the athlete lies prone on the jumping box [28]. The 30-meter sprint test is designed to measure speed ability [22] and uses a standing start, each athlete takes the best score twice in the test, and pikes are not allowed in the test. The 3000 m run is a test of aerobic endurance [22] and each athlete will only be tested once. Both the 3000m timed run and the 30m sprint run were carried out on the 400-meter standard track and field field, and all the other equipment involved in the PFT and their models/parameters are given in the S1 Table. The PFT items, scoring criteria and test criteria are all set by the NTCS event organising committee, including the Chinese Taekwondo Association and the Jiangsu Provincial Sports Bureau. The organising committee invited five elite athletes (for ethical reasons they are named A1, A2, A3, A4 and A5) from the national team to take part in the PFT2, which on the one hand helps these elite athletes to understand what level of fitness they are at, and on the other hand helps other athletes to understand the difference between their own fitness and that of the elite athletes.

According to 2020 NTCS rules, athletes who score below 50 in the PFT are directly disqualified from the competition. After the top 8 athletes are determined in each competition, the top four of these eight athletes in terms of PFT ranking go directly to the semi-finals, while the last 4 athletes are regarded as tied for fifth. The two quarter-finalists who did not advance to the final are considered to be tied for third. Since the number of athletes in each weight category is different, the percentage of PFT ranking, defined as an athlete’s PFT ranking divided by the number of athletes in his or her weight caterogy, is used in this research, regarding to it’s more meaningful to facilitate the comparison among different weight categories.

In this research, data statistics, least squares fitting and linear regression analysis were all performed with MATLAB software version R2021a.

3. Results and discussion

3.1 Correlation between competition results and PFT results

3.1.1 Total points

displays the proportion of athletes with different PFT ranking percentages among the athletes who have entered the top 8 and top 3 in the final points. The proportions were fitted to the results of PFT1, PFT2 and the average of these two (). It can be found that the proportions can be well fitted by exponential function with the shape of y = ae, where a and b are constant coefficients. The coefficients calculated by the least squares method, the Goodness of Fit (R2) and the number of athletes (N) are listed in Tables and . For all athletes, female athletes and male athletes entering the top 8 (), the R2 are very encouraging and all above 0.8, although with a slight decline when fitted with PFT2 results. This result suggests that the final total points of both male and female athletes are highly positively correlated with their PFT scores, i.e. athletes with higher PFT scores are more likely to do better in the 2020 NTCS. The fitting in entering the top 3 seems even better, except for the fitting with the of male athletes, which has the minimum R2 value (0.788). Moreover, the fitting curves in are steeper compared to , meaning that generally only athletes ranked in the top 20% of the PFT are likely to be in the top 3 in the final total points.

Relationship between total points and physical test scores.

The percentage of all athletes (top row), female athletes (middle row) and male athletes (bottom row) in each PFT ranking segment among the top 8 (a-c) and top 3 (d-f) athletes in the final total points. The blue, red and green solid lines correspond to the fitting curves of PFT1, PFT2 and , respectively.

Moreover, it is obvious that the exponential function can fit better than the linear function according to the distribution of data. This may be due to the fact that the PFT rank is the only basis for eight-to-four promotion, which means after entered the quarterfinals, the top 4 athletes in PFT will inevitably get more points than the bottom 4 ones. On the other hand, the exponential scoring rule also plays an important role in widening the points gap between athletes.

3.1.2 Entering the quarterfinals

As aforementioned, athletes who enter the semifinals are screened by PFT rankings. Thus, in order to study the relationship between athletes’ physical fitness and competition performance, the impact of the rules must be excluded. In this section, the statistics are made on the PFT results of the top 8 athletes in each competition.

illustrates that, in general, the top 10% of athletes in PFT ranking account for the highest proportion of the top 8 athletes in the four competitions. As the PFT ranks lower, this proportion is also lowers. This feature is more pronounced for the statistics of all athletes () than for females () and males () specifically. In addition, the proportion of athletes in the top 50% and bottom 50% of the PFT was also counted, which shown in with red ladders. Apparently, the top 50% account for a higher proportion of the top 8 athletes (about 2/3). For female Taekwondo athletes, the top 50% in the PFT accounted for a higher proportion in the top 8 (, implying that compared with male athletes, physical fitness is more crucial in competition performance for female athletes. A linear correlation analysis was performed on the proportions of athletes with different PFT ranking percentages among all the top 8 athletes (), all coefficients are calculated within the 95% confidence interval and p value less than 0.001. The high correlation coefficient (r = 0.914) illustrates that there is a strong negative correlation between an athlete’s probability of achieving a top 8 ranking in a competition and their percentage ranking in the PFT. Given the sample size of athletes in this study is 638, the results are considered to be statistically significant. However, it also should be noted that due to the lack of data on all athletes’ years of training and whether they have achieved international acclaims, we cannot exclude the effect of these covariates on athletes’ competitive performance.

Percentage of athletes of different PFT rankings who entering the quarterfinals.

The percentage of all athletes (a-d), female athletes (e-h) and male athletes (i-l) ranked by PFT among the top 8 athletes in the four competitions, each row in this figure is the results of one competition. The red ladders and numbers indicate the percentage of athletes in the top 50% and bottom 50% of the PFT who entering the quarterfinals.

Linear regression of the proportion of athletes in each PFT ranking interval among all the top 8 athletes in four competitions.

The regression equation and correlation coefficient are also listed.

3.1.3 Winning in semifinals

This section will discuss whether athletes with better physical fitness are more likely to win among the 4 athletes who have entered the semifinals. counted the frequencies of the first, second, third and fourth PFT ranked athletes of the four athletes who have entered the semifinals won the first place. Since both female and male competitors are divided into eight weight categories, there are a total of 16 semifinals in each competition, i.e., the sum of the numbers in each row of Table 5 is 16. For example, the number ’4’ in the first row and first column means that in the 8 female’s semifinals of the first competition, 4 of the athletes who ranked first in the PFT won the championship. Clearly, assuming that every athlete who enters the semifinals has an equal chance of winning the first place, the expectation of this value should be 2.

Table 5

Frequency statistics of top 4 athletes with different PFT rankings winning the first place.

PFT rank	No. 1		No. 2		No. 3		No. 4
Competition	Female	Male	Female	Male	Female	Male	Female	Male
1	4	3	1	3	2	2	1	0
2	3	3	3	2	1	1	1	2
3	4	3	2	2	1	2	1	1
4	5	3	0	4	2	1	1	0
Average	4	3	1.5	2.75	1.5	1.5	1	0.75

aThe PFT ranking is only a relative ranking of the four athletes who have entered the quarterfinals.

For females, the average number of times that the athlete ranked first in the PFT among those entering semifinals won the championship is 4, which is twice the expected value. The second and the third ranked athletes in the PFT have the same frequency of winning the championship, both are 1.5, which is slightly less than the expected value. The athletes ranked last in the PFT have the least frequency of winning. The same is true for male athletes, but the difference in the frequency of winning championship between the first and the second in the PFT is not as large as that of female athletes. However, the above results all confirm that PFT results are indeed related to athletes’ competitive performance, that is, athletes with better physical fitness have a greater probability of having better competitive performance. Furthermore, for female athletes entering the semifinals, the advantage brought by physical fitness may be even greater, this result is consistent with the findings of previous studies [18].

3.2 Key physical indicators

The scores of the athletes’ 5 individual PFT items are respectively counted (). As is illustrated, almost all athletes scored 19–20 points in weight-bearing squat, abdominal muscle endurance and back muscle endurance. This means that the squat strength, abdominal muscle endurance and back muscle endurance of these professional Taekwondo athletes all achieved the standard of excellence set by the General Administration of Sport of China. The gap between athletes’ PFT results mostly comes from the 30-meter sprint. Female athletes generally did not score high in the 30-meter sprint (), almost all of them scored less than 10 points. Nevertheless, compared with other athletes, the female athletes who have entered the top 8 in the competition has relatively higher scores. Male athletes had higher scores than the female athletes in the 30-meter sprint (), and similarly, top 8 athletes score higher than other athletes. Male athletes also generally perform better than female athletes in the 3000-meter run, and compared with other athletes, the percentage of top 8 athletes getting high scores is only slightly larger. For female athletes, the top 8 athletes also have a slightly better 3000m performance than other athletes.

The proportion of top 8 athletes and other athletes in each score segment of each individual PFT item.

The left column is for female athletes, and the right column is for male athletes.

Therefore, athletes with better competition results in the 2020 NTCS (those who have entered the top 8 in the competitions) tended to have higher 30-m sprint socres than other athletes demonstrates that the physical fitness gap of Taekwondo athletes mainly depends on speed ability and explosive power, which is similar to the results of previous studies [12, 29, 30]. This is also consistent with the characteristics that taekwondo is an intermittent high-intensity sport. Therefore, we can easily recommend that female athletes should pay more attention to improving their physical fitness. Especially after entered the semifinals, due to intensifying competition, the advantage of physical fitness will be more obvious.

For professional athletes, there is not much difference in leg strength, abdominal muscles, back muscle endurance and aerobic capacity, but apart from the fact that the athletes all had higher levels of these fitness categories, another potential reason could be that the scoring criteria for weighted squats, abdominal muscular endurance and back muscular endurance were too low to clearly differentiate between the athletes’ fitness levels in these categories. The low variability of athlete scores in these three items limits the discussion of the impact of these fitness indicators on the competitive performance of taekwondo athletes and is one of the limitations of this study.

3.3 PFT total scores

The average and standard deviation of PFT total scores of different weight categories athletes are counted in this section. shows that the PFT scores of female athletes are generally lower than that of male athletes, although the PFT standards of female and male are different. For both female and male athletes, the higher weight category athletes tend to obtain lower PFT scores. According to results mentioned in the previous section, this could be due to athletes with higher weights typically having relatively weaker explosive power than those with smaller weights.

PFT scores of athletes in different weight categories.

Mean value and standard deviation are represented by box and solid line respectively (p < 0.001). Scores of the national team athletes are marked by five-pointed stars.

Another interesting thing is that for almost every weight category class, the average score of the PFT2 is better than that of the PFT1. This may explain the results in section 3.1.1. That is, after the PFT1, the first and the second competitions, the athletes realized that their physical deficiencies affected their performance in the competition, so they trained to improve their physical fitness. And with its improvement, the physical fitness gap between competitors has less impact on the competition, that’s considered to be a reasonable explanation for the slight decline in R2 when fitting with PFT2 ranking percentages.

In addition, thanks to the support of the Chinese National Taekwondo Team, several Taekwondo athletes who had won Olympic or World Championships also participated in the second PFT2, and their PFT scores are also marked in . These former world champion athletes all had fitness test results above the average of the other athletes, particularly scores in A1, A2 and A3, which exceeded the average plus one standard deviation. This result also provides a strong evidence that physical fitness is a necessary condition for excellent Taekwondo athletes.

4. Conclusions

This study conducted a statistical analysis of the competition results and PFT results of the 2020 NTCS, which is the first Taekwondo major event after the General Administration of Sport of China issued the Notice and provided a relatively large data set. Overall, the results demonstrate there is a significant positive correlation between athletes’ competition performance and PFT ranking.

As athletes rank lower in PFT, their proportion of the top 8 athletes in the final total points decreases exponentially, and the proportion decline even faster of the top 3. In each competition, the top 50% in PFT account for more in the athletes entering quarterfinal. And in the semi-finals, athletes who are also ranked first in the PFT have a greater chance of coming to win the championship. The above three results all imply that the difference in physical fitness does play a key role in the athletes’ competition performance. For female athletes, the difference in physical fitness is relatively large, and there is also a large room for improvement in physical fitness; this conclusion is consistent with the conclusions in other related studies [12, 18]. Especially, the key to the difference of Taekwondo Athletes’ physical fitness lies in their explosive power, which is reflected in the biggest difference in the score of 30 meter sprint.

Furthermore, due to the PFT scores are associated with qualification for promotion in the 2020 NTCS, the athletes attached great importance to it, which makes this research more meaningful. This study is also a supplement to research on physiological indicators, as it analyses and provides a macroscopic view of the role of physical fitness in Taekwondo competitions.

The information about the equipments used in the PFT.

(XLSX)

Click here for additional data file.

Raw data.

(XLSX)

Click here for additional data file.

21 Jul 2021

PONE-D-21-18355

The relationship between physical fitness and competitive performance of Taekwondo athletes

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Reviewer #1: First and foremost, I want to congratulate the research team for undertaking an extremely difficult task, which without a shadow of doubt is linking physical fitness tests (PFT) with the actual competitive performance of professional athletes. What is more, I had little problems to understand the text in overall, despite the fact that every now and then, there were some mishaps (for instance line 190, were an unwanted “n” appeared).

I believe that martial arts practitioners (athletes and coaches alike) will find this study interesting and noteworthy.

However, in my humble opinion, there are some key factors and issues to address, in order to allow the article to be deemed worthy for publication. I shall list all of the doubts and remarks below, each in an corresponding section.

Introduction:

The cited publications do correspond with the article’s main narrative, and even in some cases directly on point. However, especially in recent years, there were some noteworthy publications regarding competitive performance, which would definitely enrich this particular section and prove the author’s scientific prowess. Please bear in mind, that any hope of tackling a macroscopic view approach, should be reflected in a slightly broadened analysis of recent scientific findings.

Materials and methods:

Starting of with a praise, the sheer amount of athletes measured is quite impressing. Inclusion of some of the most proficient taekwondo practitioners is a positive definitely worth mentioning. Another strong point is the use of MATLAB software, which is a modern tool for analysis. Unfortunately, there are some doubts on my behalf:

1) The description of the PFT test corresponds with the actual procedure of the said test, still there is no indication of any citation with scientific recognition purely devoted towards description of said test. In order to counter any doubts about the choice of PFT, appropriate citations seems more than necessary.

2) What kind of equipment was used to determine the outcomes of each of the 5 items in the PFT test? Please attach all of the manufacturer’s details, version/batch number, software release, etc. Even the most trivial items used in the study (i.e. jumping box, stopwatch), without which the test cannot be recreated otherwise, need to be described.

3) Addressing the phrases from lines 85-86, it seems only viable, to at least name the reasons (just this once) of exclusions in a bracket, i.e. (military duties, school exams, unplanned restitution, etc.).

4) After careful analysis of the attached citations, it would seem that the most troublesome aspect of the whole study is. Why did the authors decided not to include any type of a bio-monitor throughout the whole course of the research? Most of the research teams of the cited articles, did use a wide variety of scientific equipment to precisely assess the fitness level of their subjects. This is usually done in connection with main study method (like PFT in this study) in order to prove the eligibility and accuracy of the method itself. As a side note Bio-monitors record indices such as time, speed, body temperature, physiological load, mechanical load, etc. What is more, they were allowed for use, by the World Taekwondo officials during tournaments.

Results and discussion:

There was some but little struggle with understanding and following the narrative. The presented results, as well as tables, were clear to fathom upon careful inspection. Still due to sheer number of data, it was slightly difficult to decipher and process everything as a whole. I wonder if this could be remedied in any way? However, not at the cost of the data’s quality of display. If anyone would take all of the reasoning and explanations indiscriminately, then there would be no more remarks whatsoever. Unfortunately that is not the case and the most troublesome issues include:

5) Why did the research team opt not to carry out an analysis of covariance (as “main course” or as an addendum)? As stated earlier, the amount of research participants is impressive and would suffice for said analysis. It would seem beneficial to apply covariates such as:

a. Seniority (junior/senior)

b. International acclaim

c. Years of combat experience (truly not the same as point b)

d. Day of competition/testing (as stated in the article itself, there were multiple measure periods)

e. Other factors that the research team deems worthy of adding and are aware of

6) As far as I am concerned, the authors should specifically underline that only one tournament was monitored and continuing the narrative from remark number nr.5, challenge themselves against the knowledge from articles they have cited in this paper, how this can be seen as a limitation. Please bear in mind, that in at least of three of the citations, scientific data was gathered from more than one tournament.

7) Multiple times did the authors underline the benefits of introducing the PFT testing as viable method to predict and assess competitive performance of athletes. I find the presented results minimally too broad. If possible, could the authors try to make the discussion even more interesting, by speculating how should thresholds or ranges thereof look like for different types of performance. Putting it simple, how much PFT score is necessary for qualifying to cup stage, quarter finals, semis etc.?

Conclusions:

Please apply sufficient changes in the conclusions, after careful considerations of the remarks stated above. If point number 7 does seem viable for the authors, it most definitely should be sounded out in this section specifically.

I truly await responses for the above mentioned insights.

Reviewer #2: The study presents the results of original research. Described research is very interesting and conducting them during the competition time was the innovative approach. Definitely, the change of scoring rules in taekwondo has influenced the physical characteristics of top athletes. Such research can help create and develop the training programs for taekwondo competitors.

Introduction

line 39 I’m not sure what is meant by “increase in the antagonism between two competitors”. The whole sentence could be deleted.

line 40 “previous rules” maybe giving a year when they were introduce will guide the reader which rules were meant

Methods

line 77 chart of a timeline would increase the readability of the process. What is the first and second race? Do you mean the subsequent matches leading to the finals?

Did the same athletes take part in consequent races or is that organised for different groups of athletes? The number of participants suggested the second way but it was not described clearly.

Were the PFT results taken into account to be included in the further stage of competition or it didn’t have an influence on the result of the competition? It is crucial to understand how the both scores relate with each other.

line 80 change “fourth races” to “fourth race”

line 82 I believe that authors refer to Taekwondo Competition Rules, not PARA Taekwondo Competition Rules. It needs to be explained or changed.

line 84 what is meant by “professional” - does it mean that the competition was closed to amatours? If that’s true, adding selection criteria for competition would help to understand the selection process.

Other participants' characteristics are missing. No information re the age range. Is the National Taekwondo Championship Series for seniors only or junior athletes are also competing?

In the results the differentiation between the national team was addressed - it should be described in the methods section.

line 96 Table 1. How has the grading standard developed? Any references? Why is only one of the PFT grading standards different for female and male athletes?

line 99 word “produced” should be changed to “determined” or similar

Ethics statement should be provided for this study, although authors state that it is not required. It is Human Subject Research involving human participants.

Statistical methods should be described. Why and which analysis were conducted? No explanation can be found in this section and it’s difficult to find the clarity in the results descriptions.

Although authors suggest full availability of the data, they are available on the website of Chinese Taekwondo Association in Chinese. It is stated that “if anyone needs it in English, feel free to contact the corresponding author” but the english version was not provided to the reviewer. The accessibility is somehow restricted and cannot be evaluated by English-speaking reviewer.

Results

This part of the manuscript is divided into sections - the same structure could be adapted to describe statistical analysis in the Methods section.

line 107 Total points calculation should be moved to the methods section

line 133-136 The title and description of the figure should be separated.

line 149 “quarterfinals” how this term relates to the term race? The descriptions in the methods section should clearly explain that.

line 183 “eight heavyweights'' should be changed into “weight categories” or “weight divisions”. Although standard English is used, some terms in the text are misleading.

line 253 “quite good” should be changed to different, more objective term

line 255 and Fig 5 names of participants were presented - did the researchers receive the consent to use the personal details? Prior to sharing human research participant data, authors should consult with an ethics committee to ensure data are shared in accordance with participant consent and all applicable local laws. Data sharing should never compromise participant privacy. It is therefore not appropriate to publicly share personally identifiable data on human research participants.

Knowing the rationale for the inclusion of each analysis and having a clear description of which participants, from which stage of competition took part in it, would have increased the understanding of the whole research design. I believe that each analysis was conducted with the purpose but neither methodological section nor the discussion explains their value and intention in an intelligible fashion.

Conclusions

Part of this section should be added to the discussion part of the manuscript.

Had the research questions been clearly and specifically formulated in the introduction or methods, the conclusions could have been more precise.

Reviewer #3: Thank you for your interesting paper.

There are several concerns that you need to address before your paper would be publishable. Please look at my comment on the pdf version of your paper.

In summary, you need to used proper terminology with regards to Taekwondo. For example we do not use “race” in TKD but “match” or competition. there are other vocabulary that I highlighted for you.

You need to include the studies on the validity and reliability of the Physical Fitness Tests (PFT) used in this study. Who devised The scoring system used in your study and was it tested and reliable?

Your tables are very confusing and need to be redone. You have used too many tables and figures. you need to decrease the numbers and do not use table and figure to state the same data.

Your discussion portion of your paper lacks the comparison with other studies and stating the reasons behind your finding in light of the literature. This is very crucial and essential for the success of a paper.

I would not be able to agree with your conclusion since you have not provided evidence for the reliability and validity of the tests, scoring systems etc.

One last but most concerting is the ethical issues of this study. It is unethical to include the name of athletes or any identifying data about the athlete in a scientific peer reviewed paper.

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Reviewer #1: Yes: Doctor Engineer Michał Janowski

Reviewer #2: No

Reviewer #3: No

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17 Jan 2022

List of Responses

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “The relationship between physical fitness and competitive performance of Taekwondo athletes” (ID: PONE-D-21-18355). Those comments are all valuable and very helpful for revising and improving our paper, and provides guidance to us. We have studied the comments carefully and made revisions accordingly. In addition, we also upload the raw data used in our research (in supporting information), which is translated and summarised from the data in Chinese. The raw data in Chinese can be downloaded from the Chinese Taekwondo Association website (http://www.taekwondo.org.cn/). The main changes in the paper and responses to reviewers’ comments are as follows:

Reviewer #1:

1) The description of the PFT test corresponds with the actual procedure of the said test, still there is no indication of any citation with scientific recognition purely devoted towards description of said test. In order to counter any doubts about the choice of PFT, appropriate citations seems more than necessary.

Response: Thanks for your suggestion, now we have added some literatures to support the PFT used in the NTCS that we invesgated in our study (Line 101-103 in the revised manuscript).

2) What kind of equipment was used to determine the outcomes of each of the 5 items in the PFT test? Please attach all of the manufacturer’s details, version/batch number, software release, etc. Even the most trivial items used in the study (i.e. jumping box, stopwatch), without which the test cannot be recreated otherwise, need to be described.

Response: The information about the equipments are listed in the Supporting information now, including the length, weight and diameter of the barbell bar, the weight of barbell, the weight of barbell clamp, the parameter of jumping box, and the model of stopwatch. However, we don’t have access to the more detailed information, such as the manufacturers of barbell and jumping box.

3) Addressing the phrases from lines 85-86, it seems only viable, to at least name the reasons (just this once) of exclusions in a bracket, i.e. (military duties, school exams, unplanned restitution, etc.).

Response: Thanks for your reminder, we have added a few more specific reasons to explain that (Line 88 in the revised manuscript).

4) After careful analysis of the attached citations, it would seem that the most troublesome aspect of the whole study is. Why did the authors decided not to include any type of a bio-monitor throughout the whole course of the research?

Most of the research teams of the cited articles, did use a wide variety of scientific equipment to precisely assess the fitness level of their subjects. This is usually done in connection with main study method (like PFT in this study) in order to prove the eligibility and accuracy of the method itself. As a side note Bio-monitors record indices such as time, speed, body temperature, physiological load, mechanical load, etc. What is more, they were allowed for use, by the World Taekwondo officials during tournaments.

Response: Thanks for your insight into this issue. Indeed, the relationship between physiological load, mechanical load and athlete performance has been studied extensively, but our aim in this paper is to investigate the relationship between the PFT test scores and the athletic performance of taekwondo athletes. To the best of our knowledge, similar PFTs are used in the German motor test, the US Army Air Forces test, the physical fitness scoring system for naval service personnel and the national student fitness test in China (Line 101-103 in the revised manuscript). These fitness tests are quicker and more efficient than biological tests and, although more crude, reflect the macro-athletic ability of the athlete. Another equally important reason is that we only have access to data from PFT tests and not biomonitoring data, although they may exist.

5) Why did the research team opt not to carry out an analysis of covariance (as “main course” or as an addendum)? As stated earlier, the amount of research participants is impressive and would suffice for said analysis. It would seem beneficial to apply covariates such as:

a. Seniority (junior/senior)

b. International acclaim

c. Years of combat experience (truly not the same as point b)

d. Day of competition/testing (as stated in the article itself, there were multiple measure periods)

e. Other factors that the research team deems worthy of adding and are aware of

Response: Thanks for your valuable comments and suggestions. Analysis of covariance is indeed a powerful tool for excluding the influence of uncontrollable and uninteresting variables on the results, however, we do not seem to be in a position to do this analysis for several reasons. The first and most important being that we do not have relevant data such as the number of years of training of the athletes, the specific days on which each athlete took the physical tests (for example, we only know that the first phase of the PFT took place on the two days of 19 September and 20 September). Regarding the several covariates you mentioned that may have an impact on the results,

a. Seniority (junior/senior): According to the rules of the NTCS, the participants of the 2020 NTCS are professional taekwondo athletes, from the provincial or municipal teams of each province, not amateur athletes. If classify them as junior and senior, they would all be senior athletes.

b. International acclaim: We have no way of knowing whether they have received international acclaim or not.

c. Years of combat experience: As we explained earlier, this data is not available to us.

d. Day of competition/testing: The physical tests and the exact dates of each competition are undisclosed (only time slots are disclosed, for example the first leg starts on 22 September and ends on 25 September). On the other hand, for the single PFT, which lasted two days, this time difference was actually considered negligible, whereas for the two PFTs, the difference in performance due to the adjustment of the athletes' training plan was much greater. As analysed in the manuscript, after the first PFT the athletes discovered that the 30 m sprint was the key to the difference in ranks, and as a result the average grade in this item improved significantly in the second PFT.

We believe that in addition to PFT results, these variables you mentioned also have an impact on athletes' performance in competition, and the lack of such data is a major limitation of this paper, so we have included that section in the final conclusions section (Line 313-316 in the revised version).

6) As far as I am concerned, the authors should specifically underline that only one tournament was monitored and continuing the narrative from remark number nr.5, challenge themselves against the knowledge from articles they have cited in this paper, how this can be seen as a limitation. Please bear in mind, that in at least of three of the citations, scientific data was gathered from more than one tournament.

Response: Thanks for your valuable comments. However, we do not consider this to be a limitation of our study, in the literatures we cited, some collected data from multiple matches (e.g., Janowski et al., 2020; Sadowski et al., 2012; Kim et al., 2019), while others indeed collected data from only one match (e.g., Maloney et al., 2018; Bridge et al., 2014; Miller et al., 2011). For the 2020 NTCS we are studying, it is a series of four competitions, each of which is complete, from the preliminaries to the final, so it’s actually not just one competition (Line 76-83 in the revised manuscript).

Reference:

1. Janowski M, Zieliński J, Ciekot-Sołtysiak M, Schneider A, Kusy K. The effect of sports rules amendments on exercise intensity during taekwondo-specific workouts. Int J Environ Res Publ Health, 2020; 17(18): 6779.

2. Sadowski J, Gierczuk D, Miller J, Cieslinski I, Buszta M. Success factors in male WTF taekwondo juniors. J Combat Sports Martial Arts. 2012;1, 47-51.

3. Kim H-B, Jung H-C, Song J-K, Chai J-H, Lee E-J. A follow-up study on the physique, body composition, physical fitness, and isokinetic strength of female collegiate Taekwondo athletes. J Exerc Rehabil. 2015;11(1): 57.

4. Maloney MA, Renshaw I, Headrick J, Martin DT, Farrow D. Taekwondo fighting in training does not simulate the affective and cognitive demands of competition: Implications for behavior and transfer. Front Psychol. 2018;9(JAN): 25.

5. Bridge CA, Ferreira Da Silva Santos J, Chaabène H, Pieter W, Franchini E. Physical and physiological profiles of taekwondo athletes[J]. Sports Medicine. 2014;44(6): 713-733.

6. Miller J, Bujak Z, Miller M. Sports result vs. general physical fitness level of junior taekwondo athletes. J Combat Sport Martial Arts. 2011;2(1): 39-44.

7) Multiple times did the authors underline the benefits of introducing the PFT testing as viable method to predict and assess competitive performance of athletes. I find the presented results minimally too broad. If possible, could the authors try to make the discussion even more interesting, by speculating how should thresholds or ranges thereof look like for different types of performance. Putting it simple, how much PFT score is necessary for qualifying to cup stage, quarter finals, semis etc.?

Response: Thank you for your suggestion that we should enrich the discussion, and thanks for the hint. In fact, it’s hard to give a clear threshold because the fitness level of the players varies from weight categories. We have discussed a similar issue as much as possible (section 3.1.2), the results illustrate that there is a significantly negative correlation between the PFT ranking percentage and its proportion in the top 8 athletes, for example, an athlete with a PFT ranking of 10% or less has a 17% chance of reaching the top eight in the competition, while an athlete with a PFT ranking of 70%-80% has only about a 6% chance of reaching the top eight (as shown in Fig 3).

Reviewer #2:

Introduction

- line 39 I’m not sure what is meant by “increase in the antagonism between two competitors”. The whole sentence could be deleted.

Response: This statement was indeed somewhat subjective and unsupported by the literature, and we have removed it at your suggestion.

- line 40 “previous rules” maybe giving a year when they were introduce will guide the reader which rules were meant

Response: Thanks for your insight into this, we have modified it to “pre-2015 rules” (Line 39 in the revised manuscript).

Methods

- line 77 chart of a timeline would increase the readability of the process. What is the first and second race? Do you mean the subsequent matches leading to the finals?

- Did the same athletes take part in consequent races or is that organised for different groups of athletes? The number of participants suggested the second way but it was not described clearly.

- Were the PFT results taken into account to be included in the further stage of competition or it didn’t have an influence on the result of the competition? It is crucial to understand how the both scores relate with each other.

Response: We apologise for the unclear and misleading statement about the process. We have reorganised this part of the description (Section 2. Materials and methods).

Specifically, the 2020 NTCS contains four competitions and used a scoring system, (Line 76 in the revised manuscript), all the athletes were required to compete in all four competitions (Line 86-87). After each competition athletes were awarded points according to their competition ranking and the total number of points from the four competitions determines the final ranking of the athletes in the 2020 NTCS.

According to 2020 NTCS rules, athletes who score below 50 in the PFT are directly disqualified from the competition. After the top 8 players are determined in each competition in each competition, the top four of these eight athletes in terms of PFT ranking go directly to the semi-finals, while the last 4 players are regarded as tied for fifth.

- line 80 change “fourth races” to “fourth race”

- line 82 I believe that authors refer to Taekwondo Competition Rules, not PARA Taekwondo Competition Rules. It needs to be explained or changed.

Response: Thanks for your insight into this, we have modified these accordingly.

- line 84 what is meant by “professional” - does it mean that the competition was closed to amatours? If that’s true, adding selection criteria for competition would help to understand the selection process.

- Other participants' characteristics are missing. No information re the age range. Is the National Taekwondo Championship Series for seniors only or junior athletes are also competing?

Response: Yes, it means the 2020 NTCS was closed to amatours, and all the athletes were senior athletes from provincial teams in all provinces of China (Line 85-86). Unfortunately, however, the organising committee does not disclose data on the age of these athletes, their years of training and whether they have won international acclaim. This is a limitation of our study and we have added this part of discription in the Line 313-316.

- In the results the differentiation between the national team was addressed - it should be described in the methods section.

Response: Thanks for your advice, it is now added in the Line 124-128.

- line 96 Table 1. How has the grading standard developed? Any references? Why is only one of the PFT grading standards different for female and male athletes?

Response: The PFT items, scoring criteria and test criteria are all decided by the NTCS event organising committee, including the Chinese Taekwondo Association and the Jiangsu Provincial Sports Bureau. (We have added this sentence to the revised manuscript, in Line 122-124). For the scoring criteria used in the 2020 NTCS PFT, we found no published literature to prove its reliability. On the other hand, as we used the rankings of the athletes' fitness tests in our analysis, we avoided, as far as possible, the bias caused by possible uncertainties in the scoring system.

- line 99 word “produced” should be changed to “determined” or similar

Response: This word has been replaced.

- Ethics statement should be provided for this study, although authors state that it is not required. It is Human Subject Research involving human participants.

Response: We have added the Ethics statement in Line 331-335.

- Statistical methods should be described. Why and which analysis were conducted? No explanation can be found in this section and it’s difficult to find the clarity in the results descriptions.

Response: The data statistics used in this paper include each athlete's PFT score, percentage of PFT ranking, competition placements and points, and these are now descriped in the Section 2 in the revised manuscript.

Results

- This part of the manuscript is divided into sections - the same structure could be adapted to describe statistical analysis in the Methods section.

Response: Thanks for your advice, however, we think this part could be kept because the description of this part of the statistics is not sufficient to support a subsection.

- line 107 Total points calculation should be moved to the methods section

Response: Thanks for your valuable comment, we have moved this part to the section 2.

- line 133-136 The title and description of the figure should be separated.

Response: Thanks for your suggestion. We have revised them accordingly.

- line 149 “quarterfinals” how this term relates to the term race? The descriptions in the methods section should clearly explain that.

Response: Athletes entering the quarter-finals means entering the top eight, and in 2020 NTCS means they can get points. In addition, from the quarterfinals to the semifinals, the top 4 of these 8 athletes are directly selected through the PFT rankings. Therefore, in order to avoid the bias caused by this competition system to study the influence of PFT results on athletes' competitive performance, we discussed entering the quarterfinals (section 3.1.2) and winning the first place in the quarterfinals (section 3.1.3) separately.

- line 183 “eight heavyweights'' should be changed into “weight categories” or “weight divisions”. Although standardEnglish is used, some terms in the text are misleading.

Response: Thanks for your advice, all the “heavyweight” are replaced by “weight category” in the revised manuscript.

- line 253 “quite good” should be changed to different, more objective term

Response: This statement has been revised.

- line 255 and Fig 5 names of participants were presented - did the researchers receive the consent to use the personal details? Prior to sharing human research participant data, authors should consult with an ethics committee to ensure data are shared in accordance with participant consent and all applicable local laws. Data sharing should never compromise participant privacy. It is therefore not appropriate to publicly share personally identifiable data on human research participants.

Response: Thanks for your kindly reminder, we have removed all the real names of the five elite athletes that appeared in the original manuscript.

- Knowing the rationale for the inclusion of each analysis and having a clear description of which participants, from which stage of competition took part in it, would have increased the understanding of the whole research design. I believe that each analysis was conducted with the purpose but neither methodological section nor the discussion explains their value and intention in an intelligible fashion.

Response: Thanks for your valuable comments. The main aim of this paper is to study the relationship between PFT results and taekwondo athletes' competitive performance by analyzing the results of four competitions in the 2020 NTCS. In order to study this issue, we first discussed the relationship between the athletes’ total scores in four competitions and their PFT results, and found that there is an exponential positive correlation between the total scores and PFT rankings (Section 3.1.1); we conducted research on the relationship between entering the quarterfinals (section 3.1.2) and winning first place in the semi-finals (section 3.1.3) and their PFTs, respectively, and found that athletes with relatively good PFT rankings have a better chance of achieving good results in the competition; then we carried out the individual PFT results of the athletes, analysis shows that 30-meter running is a key physical fitness index that determines the athlete's competition performance (section 3.2); finally we discussed the athletes' PFTs further in section 3.3.

Conclusions

- Part of this section should be added to the discussion part of the manuscript.

- Had the research questions been clearly and specifically formulated in the introduction or methods, the conclusions could have been more precise.

Response: Thanks for your valuable comments, we have enriched the discussion in the revised manuscript. As the last paragraph of the introduction declares, the question of our study is to figure out the relationship between PFT results and taekwondo athletes' competitive performance.

Reviewer #3:

- In summary, you need to used proper terminology with regards to Taekwondo. For example we do not use “race” in TKD but “match” or competition. there are other vocabulary that I highlighted for you.

Response: Thank you for pointing this out. We have addressed all the “race” in the manuscript into “competition”.

- You need to include the studies on the validity and reliability of the Physical Fitness Tests (PFT) used in this study. Who devised The scoring system used in your study and was it tested and reliable?

- Line 87, you need to explain each component of PFT separately with reference and validity and reliability scores.

- Line 96, what is the reference for this scoring?

Response: The PFT items, scoring criteria and test criteria are all decided by the NTCS event organising committee, including the Chinese Taekwondo Association and the Jiangsu Provincial Sports Bureau. (We have added this sentence to the revised manuscript, in Line 122-124). For the scoring criteria used in the 2020 NTCS PFT, we found no published literature to prove its reliability. On the other hand, as we used the rankings of the athletes' fitness tests in our analysis, we avoided, as far as possible, the bias caused by possible uncertainties in the scoring system. And the item set-up in 2020 NTFS PFT is similar to the German motor test, the US Army Air Forces PFT, the physical fitness scoring system for naval service personnel and the national student fitness test in China (Line 101-103 in the revised manuscript).

As Fig. 4 shows, the scale does not seem to clearly differentiate between the athletes' weighted squat, back endurance and abdominal endurance abilities (almost all athletes achieved a perfect score). This could be a potential source of bias in the results as there are two explanations, one being that the professional athletes did have good leg strength, abdominal endurance and back endurance, and the other being that the standard for a perfect score was not high enough. We have added this part of the discussion to the revised manuscript (Line 316-319).

- Your tables are very confusing and need to be redone. You have used too many tables and figures. you need to decrease the numbers and do not use table and figure to state the same data.

Response: Thanks for your suggestion, but we believe that every figure and every table in the manuscript is essential to our study. Firstly, Tables 1 and 2 give the scoring rule for the 2020 NTCS and scoring criteria for the PFT, respectively, which are the basis for the results that follow; Figure 1 shows the relationship between total points and PFT results; Tables 3 and 4 list the parameters and goodness of fit of the 18 fitted curves in Figure 1, which we believe are necessary for the analysis of the results; Figure 2 shows the PFT rankings of the top eight male athletes and top eight female athletes in the four competitions; Figure 3 summarises the probability of athletes with different PFT ranking percentages reaching the Top 8 in all four competitions, which is a further insight into Figure 2; Table 5 lists the number of times athletes with different rankings won the first place after reaching the Top 4, which is also beneficial for studying the relationship between competition performance and fitness of taekwondo athletes; Figure 4 shows the difference between the individual physical test scores of athletes who reached the Final 8 and those who did not; Figure 5 compares the PFT scores of the elite national team athletes with the average PFT scores of the athletes in their weight categories, again showing the importance of physical fitness to competitive performance.

We think no two figures or tables state the same data.

- Your discussion portion of your paper lacks the comparison with other studies and stating the reasons behind your finding in light of the literature. This is very crucial and essential for the success of a paper.

Response: Yes we totally agree with you that the comparison with other studies is very crucial for a research paper, actually we have worked hard to do this, for example, in Line 233, Line 257 and Line 305. However, as there are not many relevant studies, more comparisons seem very challenging.

- One last but most concerting is the ethical issues of this study. It is unethical to include the name of athletes or any identifying data about the athlete in a scientific peer reviewed paper

Response: Thanks for your kindly reminder, we have removed the names of any athletes involved in the paper.

- Line 99, was this base on PFT scores or TKD competition?

- Line 101, why? This could be a source of bias.

Response: This is based on PFT scores. Because according to the rule of 2020 NTCS, after the top 8 players are determined, the top 4 of these 8 athletes in term of PFT ranking will go directly to semi-finals, but not based on TKD competition. We acknowledge that this system may create some bias, mainly in that it is possible that athletes who do not do well in the PFT also have the opportunity to advance in the 8-in-4. This bias may be responsible for the exponential, rather than linear, relationship illustrated in Figure 1 when discussing the relationship between the final total score and PFT result (discussed in Line 188-192). Therefore, in order to avoid this bias, the relationship between " Entering the quarterfinals" (section 3.1.2) and " Winning in semifinals" (section 3.1.3) and the PFT results are analysed and discussed separately.

- Line 110, is this your idea or has it been published and validated?

Response: The organising committee of the 2020 NTCS gave the rules for points, as shown in Table 1, with 100 points for first place, 60 points for second place, 36 points for third place and 21.6 points for fourth place. When we trace the exponential relationship between total points and the PFT results (section 3.1.1), we found that the scoring rule of 2020 NTCS can also be expressed exactly as an exponential function. We have therefore summarised the scoring rule of 2020 NTCS as a exponential function, which can be easier for other tournaments to refer to and generalise, and it is easy to verify this formula.

- Line 187, this s very confusing. Was there only one competition? Are you referring to each match and each race? You need to clarify by winning the competition do you mean the athlete got gold medal?

- Line 189, this is very confusing which one is the athlete's rank in PFT and which one is their rank in the competition?

Response: Perhaps the introduction of the 2020 NTCS was not presented clearly enough before, which led to the confusion here. We have now revised the writting of the 2020 NTCS competition rules and PFT rules in the methods section and hope to make the results and discussion in this section clearer.

As the 8-in-4 is directly determined by the PFT results and not the competition results (as discussed earlier, there may be some bias here), in order to examine the relationship between athletes' competition performance and fitness levels, we need to devide the discussion into two parts, one is that presented in section 3.1.2, the other one is “whether athletes with better PFT results have a higher probability of winning the first place after reaching the semifinal” as discussed in this section.

There are 4 competitions in 2020 NTCS (first column in Table 5), in the case of the male athelets, for example, each competition produced eight players who were first place, as there were eight weight categories. For these 8 first place athletes, it is helpful to count their PFT ranking among the top four athletes in their respective weight categories. Assuming there is no relationship between competition performance and fitness, the number of times the No. 1, No. 2, No. 3 and No. 4 ranked athletes in the PFT have won first place in a competition should all be 2, however, actually it is 4, 1, 2, and 1 (as the first line of number in Table 5), which means that the athlete who ranks first in the physical test among these four is more likely to win first place in the competition.

- Line 218, were these differences statistically significant? Please state.

Response: This phrase was considered too colloquial and also redundant, so we deleted it.

- Line 236, how are these compared to other sports and other references. In your discussion you need to compare your results to other papers and state the reasons.

Response: The comparisons we make here are between the athletes studied in this paper, as the exact same fitness test criteria are not used in the other literature, we are unable to make comparisons with other sports and other references. In fact this conclusion can already be drawn from Figure 5.

- Line 254, higher than who and what is you reference?

Response: Thanks for your comment, we have reorganized this sentence, now it’s in the Line 286-290 in the revised manuscipt.

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11 Feb 2022

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Additional Editor Comments:

The comments of the reviewer should be fully complied with.

Descriptions of figures are unclear and it is difficult for the reader to fully accurately interpret the presented data - the quality of figure descriptions and their descriptions under the figures should be clearly improved.

Lines 173-174 - Remove this torch "high-flown" stylistically sentence (Remove this torch "high-flown" stylistically sentence (“Potential possible causes for this phenomenon will be discussed later”).  At the same time, make it clear in the discussion that you are referring to these observations from the results.

Consider adding legends under the tables to help the reader understand the tables.

Tables should be properly edited to make it easier to follow (breaking descriptions into lines makes it difficult.

The name of table 4 (description) is unreliable. The table should be fully and properly named so as not to raise doubts and not to send the reader to look for elsewhere.

Statements such as "This feature is more obvious for" should be limited - statements "obvious" are not entirely accurate in the discussed contexts.

Again - the description in tables, figures and in the text must allow for an authoritative and unambiguous assessment of what they refer to and what they indicate. At the moment, only the reader who has read the work very carefully, are they clear. It is necessary to precisely and clearly describe what and what these figures indicate, with whom and when.

Lines 256-257 – “…athletes are pretty good.” – reword this using more scientific language and past time.

Line 258 – avoid using abbreviations  “didn’t”.

Consider whether in every context in the work naming athletes who train taekwondo as "players" is reliable - I have some concerns here.

The discussion is quite poor when it comes to comparisons with other studies.

A large part of the conclusions and limitations is basically a discussion - please move it to the previous section. Limit your conclusions to what has actually been shown.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #3: No

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: No

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #3: No

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Starting off with a appraise, the Authors managed to address most of the issues pinpointed by the reviewers, in an orderly and clear manner. Necessary addendums as well as removals have substantially enriched the text as a whole. As stated previously, some of the less fortunate terms were present, but the Authors managed to correct them this time.

Without further ado, I shall voice out the most important aspects of the current state of the article:

1) The Description of the PFT test…

From where I am standing, the addendums in lines 101-103 clear out any doubts.

2) What kind of equipment was used…

Necessary corrections have been applied. It is perfectly understandable, that some of the more “mundane” and “less spectacular” items may have been manufactured so long ago, that the detailed information may have been next to impossible to obtain.

3) Addressing the phrases from lines 85-86…

The abovementioned issue has been addressed accordingly.

4) After careful analysis of the attached citations…

The Authors did underline the separation from biomonitoring towards a more macro-athletic approach. The limitations were provided in the renewed version of the manuscript.

5) Why did the research team opt not to carry out an analysis…

The most hampering limitations were added by the research team in lines 313-316. The provided reasons are understandable and I strongly encourage taking them into consideration, which may finally result in obtaining data viable for an analysis of covariance. Maybe it was not aired specifically enough – no World/Asian/Olympic/Cup medalists whatsoever in said group? Just a general quota would suffice – i.e. 11 gold/22 silver/33 bronze etc.

6) As far as I am concerned, the Authors should specifically underline…

The appropriate lines and addendums were administered by the Authors.

7) Multiple times did the Authors underline the benefits of introducing the PFT testing…

In the light of multiple alterations carried out in the text, my initial doubts have been dispelled. The percentages presented in Figure nr.2 are clear. Still, I strongly suggest tackling the issue in future research regarding thresholds in the PFT test.

Reviewer #3: Thank you for your revisions. It reads much better.

However, you have not provided any evidence/references on the individual tests of the PFT reliability, validity or any reference on the way they were performed in your study or the normal values of each test in comparison to TKD athletes in your study. You have not explain the utility of each test and significance of each test physiologically and why they should be included in the battery of the tests. You also have not provided any p values for the differences you mentioned in various athlete groups, male versus female to show statistical significance.

As such, unfortunately in my opinion your manuscript in not publishable in its present form.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #3: No

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20 Mar 2022

Responses to the Editor and Reviewers

Dear Editor Durkalec-Michalski,

Thanks for your valuable comments. In the following we answer each specific point (in blue).

Descriptions of figures are unclear and it is difficult for the reader to fully accurately interpret the presented data - the quality of figure descriptions and their descriptions under the figures should be clearly improved.

Thanks for your insight into this. We have improved the description of the figures, both in the text and in the legend, especially the descriptions of Figs 1 to 4 have been significantly modified. The missing legend has been added to Fig 2 (red ladders). We hope these modifications could make the figures easier to understand.

Lines 173-174 - Remove this torch "high-flown" stylistically sentence (“Potential possible causes for this phenomenon will be discussed later”). At the same time, make it clear in the discussion that you are referring to these observations from the results.

Sorry for the colloquial expressions, this sentence has been removed. And we have made it clear that the discussion was based on the results in the previous section, for example, in Line 303 of the revised manuscript we stated that "This may explain the results in section 3.1.1."

Consider adding legends under the tables to help the reader understand the tables.

Thanks for the valuable suggestion, we have now added some legends to make the table easier to understand, e.g., Table 3 and Table 5.

Tables should be properly edited to make it easier to follow (breaking descriptions into lines makes it difficult.

We have rearranged Tables 3 and 4, which may not be easy to follow as mentioned by the editor.

The name of table 4 (description) is unreliable. The table should be fully and properly named so as not to raise doubts and not to send the reader to look for elsewhere.

This too brief description has now been reformulated to "Table 4. The fitting coefficient (a and b), the Goodness of Fit (R2) and the number of athletes (N) in Fig. 1d-e. "

Statements such as "This feature is more obvious for" should be limited - statements "obvious" are not entirely accurate in the discussed contexts.

Thank you for pointing this out, we have replaced the word "obvious" to "pronounced" to make it more academic.

Again - the description in tables, figures and in the text must allow for an authoritative and unambiguous assessment of what they refer to and what they indicate. At the moment, only the reader who has read the work very carefully, are they clear. It is necessary to precisely and clearly describe what and what these figures indicate, with whom and when.

We agree with the editor that the description of the figures and tables should be clear and easy to understand, and we have modified almost every figure and table description in the text accordingly for this purpose.

Lines 256-257 – “…athletes are pretty good.” – reword this using more scientific language and past time. (Line 239?)

Thanks for the advice, we have now reformulated this sentence to read "This means that … of these professional Taekwondo athletes all achieved the standard of excellence set by the General Administration of Sport of China."

Line 258 – avoid using abbreviations “didn’t”. (Line 240?)

This abbreviation has been revised.

Consider whether in every context in the work naming athletes who train taekwondo as "players" is reliable - I have some concerns here.

We agree with the editor that "players" may be not a appropriate word here, we have replaced this word with "athletes" in the revised manuscript.

The discussion is quite poor when it comes to comparisons with other studies.

In this revised version, we have made significant modifications in the section 3 (Results and discussion) according to the editor and the reviewer’s suggestions, which, we hope, has improved the disussion and made it more clear. Some major modifications, including but not limited to Lines 159-162, Lines 208-211, Lines 272-280 and Lines 286-288.

A large part of the conclusions and limitations is basically a discussion - please move it to the previous section. Limit your conclusions to what has actually been shown.

Thanks for pointing out this, we agree with the editor that that some sentences should be placed in the discussion section, specifically, we have moved Lines 313-316 in the previous manuscript to Lines 208-211 in the revised version, moved Lines 316-319 in the previous manuscript to Lines 286-288 in the revised version. Some other modifications in the conclusions could also be clear seen in the tracked version of manuscript.

Reviewer #1: Starting off with a appraise, the Authors managed to address most of the issues pinpointed by the reviewers, in an orderly and clear manner. Necessary addendums as well as removals have substantially enriched the text as a whole. As stated previously, some of the less fortunate terms were present, but the Authors managed to correct them this time.

Thanks for your overall comments. In the following we answer each specific point (in blue).

Without further ado, I shall voice out the most important aspects of the current state of the article:

1) The Description of the PFT test…

From where I am standing, the addendums in lines 101-103 clear out any doubts.

Thank you, further modifications have also been made in this revision, for example, in Lines 105-109, Lines 110-111 and Lines 125-126 in the revised manuscript.

2) What kind of equipment was used…

Necessary corrections have been applied. It is perfectly understandable, that some of the more “mundane” and “less spectacular” items may have been manufactured so long ago, that the detailed information may have been next to impossible to obtain.

Thank you for your understanding, we agree with the reviewer that these informations are important for other researchers.

3) Addressing the phrases from lines 85-86…

The abovementioned issue has been addressed accordingly.

4) After careful analysis of the attached citations…

The Authors did underline the separation from biomonitoring towards a more macro-athletic approach. The limitations were provided in the renewed version of the manuscript.

Thanks for your comment, although this more macro-athletic approach has its limitations, we think it is still meaningful as it is at least a complement to the bioassay approach.

5) Why did the research team opt not to carry out an analysis…

The most hampering limitations were added by the research team in lines 313-316. The provided reasons are understandable and I strongly encourage taking them into consideration, which may finally result in obtaining data viable for an analysis of covariance. Maybe it was not aired specifically enough – no World/Asian/Olympic/Cup medalists whatsoever in said group? Just a general quota would suffice – i.e. 11 gold/22 silver/33 bronze etc.

Thanks for the reviewer’s suggestions, and we understand the concerns of the reviewer. We are sorry that we are not in a position to adopt this recommendation as we failed to obtain these additional information. However, we believe that these additional information, although beneficial for doing an analysis of covariance, will not affect the main findings of this study. Athletes' competitive performance is certainly also related to other factors such as taekwondo skills, mental fitness and competition experience (which would be related to whether or not they have previously won honours), but as our study only discusses the relationship between athletes' physical test scores and their competitive performance, the current data and statistics should be sufficient to justify the conclusions of this paper.

6) As far as I am concerned, the Authors should specifically underline…

The appropriate lines and addendums were administered by the Authors.

7) Multiple times did the Authors underline the benefits of introducing the PFT testing…

In the light of multiple alterations carried out in the text, my initial doubts have been dispelled. The percentages presented in Figure nr.2 are clear. Still, I strongly suggest tackling the issue in future research regarding thresholds in the PFT test.

Thanks for you valuable suggestion, some of the limitations in this study will be discussed and improved upon in more detail in subsequent studies.

Reviewer #3: Thank you for your revisions. It reads much better.

Thank you for your contribution to the improvement of this manuscript. In the following we answer each specific point (in blue).

However, you have not provided any evidence/references on the individual tests of the PFT reliability, validity or any reference on the way they were performed in your study or the normal values of each test in comparison to TKD athletes in your study. You have not explain the utility of each test and significance of each test physiologically and why they should be included in the battery of the tests.

Thanks for your valuable comments and sorry for the limited description of the physical fitness test in previous manuscripts. We have added the meanings of this battery of physical tests to the text, which reads "This battery of tests can be considered as an indicator stand for various aspects of an athlete's athletic ability, including agility, explosive power, strength, aerobic capacity and anaerobic capacity, which has been viewed as a multidimensional structure that reflects motor performance ability [27]", and indicated the utility and physiological significance of each individual test, for example, "Weight-bearing squat is used to test the strength of the quadriceps, gluteus maximus and other lower limb muscles [28]. ", "The 30-meter sprint test is designed to measure speed ability [23]", "The 3000 m run is a test of aerobic endurance [23]", whereas abdominal and back endurance are measured in a similar way to [29] (but not exactly the same), the specific details of each individual test are set out in the revised manuscript (Lines 110-133).

Unfortunately no reference was found to demonstrate what normal values should be achieved by TKD athletes in these individual tests. However, we believe that since the subject of our study in this paper is to compare the relationship between competitional performance and physical test scores among these professional TKD athletes who participated the 2020 NTCS, and not to compare them with other athletes, the absence of the "normal values" seems does not affect the conclusions.

You also have not provided any p values for the differences you mentioned in various athlete groups, male versus female to show statistical significance.

Sorry the unclear writing, we have tried to clarify this in the previous manuscript in Lines 142-143, which reads "All p-values in this article are less than 0.001, and will not be marked hereafter", however, it seems not clear enough especially as the reader tends to forget this when reading later. We have now removed the Lines 142-143 in the previous version of manuscript and instead, we have clarified p-values where they occur. For example, in Line 204 and Line 299.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

11 Apr 2022

11 Apr 2022

Responses to the reviewers

Reviewers' comments to the Author:

Reviewer #3: Thank you for the revisions. All my concerns have been addressed. However, there some grammatical and other minor errors that require revisions as follow:

Thanks for your careful checking. We have corrected all the following typos and grammatical errors the reviewer raised.

line 25: specifically in increase of explosive power. please change to "specially enhancing the explosive power."

Modified.

Line 57, "the PFTs performed are all conducted". change to: "the PFTs performed were all conducted"

Corrected.

Line 61, "Aware of the important role"change to "Being aware of..."

Corrected.

Line 76, "The 2020 NTCS contains four competitions, two PFTs and used a scoring system.", change to, "The 2020 NTCS contained four competitions, two PFTs and a scoring system."

Modified.

Line 116, "endurance of the abdominal muscles, the test subject lies prone on a jump box with the"

Should be, "endurance of the abdominal muscles, the test subject lies supine on a jump box with the"

Corrected.

Line 120-121, "back muscle endurance is the same as abdominal muscle endurance, except that the athlete lies on the jumping box" should be:"back muscle endurance is the same as abdominal muscle endurance, except that the athlete lies prone on the jumping box"

Corrected.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

14 Apr 2022

The relationship between physical fitness and competitive performance of Taekwondo athletes

PONE-D-21-18355R3

Dear Dr. Lumin He ,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Krzysztof Durkalec-Michalski, Ph.D

Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: I would like to thank the Authors for addressing all my concerns. The manuscript at the present form is readable and publishable.

Kind Regards

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: No

8 Jun 2022

PONE-D-21-18355R3

The relationship between physical fitness and competitive performance of Taekwondo athletes

Dear Dr. He:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

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on behalf of

Dr. Krzysztof Durkalec-Michalski

Academic Editor

PLOS ONE

Table 1

Scoring rule of the 2020 NTCS.

Rank	No. 1	No. 2	Joint third	Joint fifth
	(M = 1)	(M = 2)	(M = 3)	(M = 4)
Point	100	60	36	21.6

Table 2

Assessment matrix for the physical fitness test.

Score	Weight-bearing squat (Multiples of weight)	30-meter run (s)	Back muscle endurance (s)	Abdominal muscle endurance (s)	3000-meter run
					(minute:second)
					Male	Female
20	≥1.2	≤4.5	≥120	≥120	≤11:00	≤11:30
19	1.18	4.55	118–119	118–119	11:01–11:10	11:31–11:40
18	1.16	4.6	116–117	116–117	11:11–11:20	11:41–11:50
17	1.14	4.65	114–115	114–115	11:21–11:25	11:51–11:55
16	1.12	4.7	112–113	112–113	11:26–11:30	11:56–12:00
15	1.1	4.75	110–111	110–111	11:31–11:35	12:01–12:05
14	1.08	4.8	108–109	108–109	11:36–11:40	12:06–12:10
13	1.06	4.85	106–107	106–107	11:41–11:45	12:11–12:15
12	1.04	4.9	104–105	104–105	11:46–11:50	12:16–12:20
11	1.02	4.95	102–103	102–103	11:51–11:55	12:21–12:25
10	1.0	5.0	100–101	100–101	11:56–12:00	12:26–12:30
9	0.95	5.05	95–99	95–99	12:01–12:10	12:31–12:40
8	0.9	5.1	90–94	90–94	12:11–12:20	12:41–12:50
7	0.85	5.15	85–89	85–89	12:21–12:30	12:51–13:00
6	0.8	5.2	80–84	80–84	12:31–12:45	13:01–13:15
5	0.75	5.25	75–79	75–79	12:46–13:00	13:16–13:30
4	0.7	5.3	70–74	70–74	13:01–13:15	13:31–13:45
3	0.65	5.35	65–69	65–69	13:16–13:30	13:46–14:00
2	0.6	5.4	60–64	60–64	13:31–13:45	14:01–14:15
1	0.55	5.45	30–59	30–59	13:46–14:00	14:16–14:30
0	≤0.5	>5.5	<30	<30	>14:00	>14:30

Table 3

The fitting coefficient (a and b), the Goodness of Fit (R2) and the number of athletes (N) in Fig 1A–1C.

		a	b	R2	N
All	PFT1	0.305 ± 0.037	-2.861 ± 0.505	0.974	573
	PFT2	0.276 ± 0.067	-2.490 ± 0.913	0.890	520
		0.287 ± 0.043	-2.626 ± 0.579	0.959	638
Female	PFT1	0.289 ± 0.072	-2.641 ± 0.978	0.893	219
	PFT2	0.265 ± 0.081	-2.354 ± 1.097	0.834	206
		0.264 ± 0.068	-2.346 ± 0.926	0.873	245
Male	PFT1	0.326 ± 0.079	-3.149 ± 1.093	0.907	354
	PFT2	0.288 ± 0.094	-2.649 ± 1.280	0.827	314
		0.315 ± 0.043	-2.956 ± 0.591	0.968	393

aThe coefficients a and b are in the form of mean and 99% confidence interval.

Table 4

The fitting coefficient (a and b), the Goodness of Fit (R2) and the number of athletes (N) in Fig 1D and 1E.

		a	b	R2
All	PFT1	0.602 ± 0.054	-5.811 ± 0.719	0.992
	PFT2	0.497 ± 0.135	-4.635 ± 1.753	0.925
		0.570 ± 0.129	-5.710 ± 1.771	0.951
Female	PFT1	0.630 ± 0.151	-5.975 ± 1.958	0.945
	PFT2	0.434 ± 0.120	-3.898 ± 1.520	0.916
		0.581 ± 0.149	-6.104 ± 2.137	0.938
Male	PFT1	0.573 ± 0.102	-5.641 ± 1.386	0.969
	PFT2	0.582 ± 0.243	-5.600 ± 3.218	0.854
		0.567 ± 0.295	-5.453 ± 3.899	0.788