Responsiveness of the Calf-Raise Senior test in community-dwelling older adults undergoing an exercise intervention program.

INTRODUCTION: Mobility significantly depends on the ankle muscles' strength which is particularly relevant for the performance of daily activities. Few tools are available, to assess ankle strength with all of the measurement properties tested. The purpose of this study is to test the responsiveness of Calf-Raise Senior Test (CRS) in a sample of elderly participants undergoing a 24-week community exercise program.
METHODS: 82 older adults participated in an exercise program and were assessed with CRS Test and 30-second chair stand test (CS) at baseline and at follow-up. Effect size (ES), standardized response mean (SRM) and minimal detectable change (MDC) measures were calculated for the CRS and CS tests scores. ROC curves analysis was used to define a cut-off representing the minimally important difference of Calf-Raise Senior test.
RESULTS: Results revealed a small (ES = 0.42) to moderate (SRM = 0.51) responsiveness in plantar-flexion strength and power across time, which was lower than that of CS test (ES = 0.64, SRM = 0.67). The responsiveness of CRS test was more evident in groups of subjects with lower initial scores. A minimal important difference (MID) of 3.5 repetitions and a minimal detectable change (MDC) of 4.6 was found for the CRS.
CONCLUSION: Calf-Raise Senior Test is a useful field test to assess elderly ankle function, with moderate responsiveness properties. The cutoff scores of MDC and MID presented in this study can be useful in determining the success of interventions aiming at improving mobility in senior participants.

Introduction

Population aging is a major global demographic trend. The increase in life expectancy raises the related concern of increasing morbidity, prolonged disability and dependency, with a reduction in quality of life [1]. This demographic transition is influencing the economy, care, social development, welfare and well-being. Thus, it is crucial to adapt policy, health services and intervention programs to an aging and frailer population.

The quality of life of the elderly depends on their health and ability to perform activities of daily living (ADLs) [2]. Mobility is a prerequisite for the performance of most common ADLs and its maintenance is a major goal of geriatric health professionals [3]. Mobility greatly depends on the strength in the lower limbs, especially in the ankle muscles, which are particularly relevant in gait function [2, 4, 5] climbing stairs and rising from a chair [5-7]. Plantar-flexors (PF) muscles act to support and to propel the body forward in late stance and their strength is positively related to gait velocity and step length [8]. Lower strength levels are very common in older adults [9, 10] and are associated with poor gait and balance [11, 12]. PF muscles, in particular, reveal large decline in strength with aging, presenting a decrease of 2.3% in very old adults (>85 years-old) per year [13], and differences of about 40% when comparing elderly with young men [14, 15].

PF assessment is especially important to design programs or implement strategies, aiming the preservation of the mobility. This issue is even more relevant in the design of exercise programs tailored to functional status of older adults [16-18]. In order to ensure meaningful and quality data related to the functional loss and changes in mobility parameters with age, the use of measurement tools with relevant psychometric properties is essential. Studies reporting validity and responsiveness of strength and mobility assessment tools are relatively scarce [19, 20]. Additionally, few of the aforementioned studies report sensibility and sensitivity data, allowing the establishment of the minimal importance difference. To our knowledge, only the “30 second chair stand test” (CS) [19] and the “Timed Up and Go” (TUG) [20] have been tested for responsiveness in community-setting interventions with healthy and independent older adults. Although both tests are used to assess lower limbs muscle function, none of them provides specific information about the PF strength, which has already been mentioned as being relevant for preserving the quality of gait in the elderly [2, 4–5]

The Calf-Raise Senior (CRS) test is the only field assessment tool developed to evaluate ankle muscle function in the elderly and has shown to have an excellent test-retest reliability (ICC = 0.90), inter-rater reliability (ICC = 0.93–0.96) and a good intra-rater reliability (ICC = 0.79–0.84) [21,22]. The test also presented a significant association between its scores and laboratory strength assessments (isometric, r = 0.87, r2 = 0.75; isokinetic, r = 0.86, r2 = 0.74; and rate of force development, r = 0.77, r2 = 0.59), demonstrating to be an excellent indicator of ankle strength in older adults [21]. Despite good results regarding the reliability and validity of the CRS test [21,22], its responsiveness has not yet been established. Therefore, the purpose of this study is to test the responsiveness of the CRS test in a sample of elderly participants undergoing a 24 weeks’ community exercise program.

Materials and methods

Study design and subjects

A prospective multi-site cohort study was conducted, with a 24-week follow-up period. The follow up interval was defined by having into account that although major adaptations in strength and power in the elderly occur after 12 weeks of training [23-25] higher effect has been showed after longer training periods (≥24 weeks) [26]. All participants underwent a multicomponent community-based exercise intervention included in the “More Active Aging Project” (MAAP), which was implemented in 5 municipalities in the West and Ribatejo Regions of Portugal. The study was coordinated by the Faculty of Human Kinetics, University of Lisbon and Sport Sciences School of Rio Maior, between September 2014 and December 2015. All detailed information about the protocol and methods used in the MAAP intervention can be found in Ramalho et al. [27].

A sample of 82 older adults from the abovementioned cohort was recruited through advertising in local centers and sports community services by a multi-stage sample method. Using the results from our previous study [21], the minimum sample size of 61 participants was determined, considering and effect size of d = 0.80, with 80% power and alpha at 0.

To be considered eligible for this study, participants should be 65 years or more, live independently in the community, be autonomous and correctly understand the Portuguese language. Exclusion criteria were considered: self-reported cognitive, neurological, bone and joints, or other impairments that could inhibit the performance of exercises in the standing position autonomously; inability to walk independently and/or without assistance of a walking aid and not having a hip or knee prosthesis.

A written informed consent was obtained from all participants at the beginning of the intervention. The Faculty of Human Kinetics Ethics Committee (Lisbon University) approved the study protocol.

Exercise program

The MAAP 24-weeks exercise program comprised group-based multicomponent 50-min exercise sessions twice a week. Graduated exercise specialists received 20 hours of training regarding the program methodology and follow-up guidelines during the intervention period. The structure of the exercise program is fully explained elsewhere [27]. In brief, the program aims to develop postural control, balance (static and dynamic), endurance, mobility, walking pattern, and to improve strength and muscle resistance. In order to provide continuous and progressive stimulus to the participants’ functional capacities, weekly progressive changes in intensity and complexity, and monthly variation in exercise mode, were incorporated into the program. The progression of the exercise program was controlled through periodic and unscheduled visits by the research team, in order to verify the compliance of the guidelines. Additionally, the instructors recorded a monthly qualitative classification of the participants’ performance.

Assessments

All assessments were conducted at baseline (BL) and after 24 weeks (follow-up, FU) and were administered by examiners who received specific training in applying the test protocols.

To evaluate the eligibility of participants, a health and falls assessment questionnaire designed and validated by the Portuguese Language and Culture [28] was administered through face-to-face interviews. The questionnaire included questions about demographics, health, self-perception status, medication intake, medical history, and falls history. It was used to verify the eligibility of participants in the study, as well as, identifying health conditions that could prevent participation in the exercise program sessions and interfere with performance in the assessment tests.

All participants were evaluated using the CRS and CS tests on the same day in each phase (BL and FU) by the same examiners. The CS test was chosen as an external reference measure (anchor) in this study, as it measures the same attribute of the CRS (lower limbs strength) and presents results that can be partially explained by the PF strength (β = 0.358, P = 0.074) [29]. The CS test protocol consists of the performance of the maximum possible repetitions of the stand/sit down movements in 30 seconds [19]. The test was administered using an armless chair (height: 43.2 cm), which was supported against a wall to ensure stability. The final score corresponded to the total number of complete cycles performed, i.e., the participants should extend their knees and sit fully on the chair, not lift the feet off the floor and keep the arms folded over the chest. The CRS test protocol is fully described elsewhere [21]. Briefly, the protocol includes the performance of a maximum number of heel lifting / lowering repetitions in the standing position, in 30 seconds, with the knees extended, at maximum possible range and velocity, without transferring the body weight to the hands. The test score corresponded to the number of cycles correctly executed at the end of 30 seconds.

Data analyses

Descriptive statistical analyses were performed to characterize the sample. Central tendency parameters were determined for continuous variables (mean, standard deviation and median) and relative frequency was calculated for categorical and ordinal variables. The normal distribution of continuous variables was checked with the Kolmogorov-Smirnov Test.

The responsiveness of the CRS test was determined using two different methods: a distribution-based approach and an anchor-based approach.

For the distribution-based approach the results of the two assessment phases were used to calculate the change in scores (FU score—BL score) of the CRS and CS tests. The following statistical parameters, commonly used to assess the responsiveness of instruments, were computed: 1) Effect size (ES)—provides information about the magnitude of change over time by dividing the Mean Change Score of a variable by the SD of its BL Scores[30,31]. To interpret the effect-size data, the cutoff points proposed by Hopkins [32] (ES < 0.20 = trivial effect; 0.20 ≥ ES < 0.60 = small effect; 0.60 ≥ ES < 1.20 = moderate effect; 1.20 ≥ ES < 2.0 = large effect; 2.0 ≥ ES < 4.0 = very large; and ES ≥ 4.0 = nearly perfect); 2) Standardized response mean (SRM)—parameter that indicates if the change of the results over time were large relative to the variability in the measurements. The SRM can be calculated as the Mean Change Score of the variable divided by the SD of the same Change Score. SRM values of 0.20, 0.50, and 0.80 are considered as small, moderate and large change, respectively [33]; 3) Minimal Detectable Change (MDC)—measure that reflects the smallest change in score that can be interpreted as a ‘true’ change, i.e. beyond measurement error [34]. The formula for the calculation of MDC can be expressed as: 1.96 (√2 x Standard Error of Measurement). The calculation of the Standard Error of Measurement was based on the results of our previous study using the following equation: SEM = SD of BL scores (√1-ICC). The proportion of participants achieving a degree of improvement beyond the MDC was then determined [35].

The anchor-based approach was performed using a Receiver Operating Characteristic (ROC) curve analysis in order to verify whether the CRS test could discriminate between participants with positive change (improved) versus no change (stable) [36,37]. The cut-off of 3.01 was considered to dichotomize sample in accordance with the minimal detectable change (MDC) determined in a previous test-retest reliability study (CS change score < 3.01 = stable group; CS change score ≥ 3.01 = improved group). An area under the curve (AUC) was used to determine specificity and sensitivity [38], and the cut-off corresponding to the point closer to the upper left corner was defined as the score that best classifies participants who had improved or maintained their state. This cut-off represents the “minimally important difference” (MID) of this test [34], that is, the smallest change in the CRS scores that is considered clinically relevant, or worthwhile to the participants [35], also frequently referred to in the literature as the “minimal clinically important difference” (MCID) [36, 39]. Paired t-tests (or non-parametric Wilcoxon tests) were used to compare data at BL and FU within groups of change.

Results

Eighty two healthy older adults were eligible to participate in the responsiveness study of the CRS test. All participants were present in both assessment periods and met a minimum attendance threshold in the training sessions. Furthermore, none of the participants showed signs of overexertion, pain in the lower limbs or other signs of discomfort that prevented them from complying with the requirements for a satisfactory assessment.

Participants were mainly women (87.8%) with good general health perception (≥3 points-scale) and a mean BMI of 29.9±5.1 kg/m2 (Table 1), indicating that this group is overweight (≥ 25,0 kg/m2) [40], although out of the range for increased mortality risk (BMI <23.0 or > 33.0) [41].

Table 1

Demographics and functional fitness measures in baseline from the total group of participants and subgroups of CRS scores.

Demographic and health parameters
N = 82	Mean ± SD (median)/ %
Age (years)	72.3 ± 5.0 (72,0)
Gender, female (%)	87.8
BMI (kg/m2)	29.9 ± 5.2 (29.4)
HPS (1–4 scale)	3,3 ± 0,8 (3,0)
Functional fitness parameters
N = 82	Mean ± SD (median)/ %
CRS (x/30s)	25.0 ± 8,8 (24,0)
CS (x/30s)	16,1 ± 4,6 (15,5)

Data are presented as mean ± standard deviation (median) for continuous variables, and percentage for categorical variables on Baseline.

Abbreviations: BMI = Body mass index; HPS = Health Perception Status; CRS = Calf-raise Senior test; CS = 30 s chair stand test.

In general, participants underwent statistically significant improvements in their lower limb strength (CRS and CS, P < 0.001). Regarding the distribution-based approach, the effect size was low to moderate, ranging from 0.4 to 0.6 (CRS and CS, respectively) and SRM values were moderate, ranging from 0.5 to 0.7 (Table 2).

Table 2

Responsiveness of FF measures for the Total Sample and by Subgroups of Lower and Higher CRS Scores.

	Change Score (N = 82)
Parameters	mean	± SD (median)	ES	SRM
CRS score (x/30s)	3.4	± 6.6 (3.0)	0.4	0.5*
CS score (x/30s)	3.6	± 5.3 (3.0)	0.6†	0.7*

Data are presented as mean ± standard deviation (median). Cohen’s Effect Size (ES) and Standardized Response Mean (SRM) from the comparison between baseline and follow up scores. Dagger (†) indicates ES|d| > 0.6 and asterisk (*) indicates SRM > 0.5 (medium to high Effect Size or response mean, here considered as important differences between group means).

Abbreviations: CRS = Calf-raise Senior test; CS = 30 s chair stand test; ES: Effect Size; SRM = standardized response mean.

The change detected using the CRS was higher, by a statistically significant difference, for the group of participants who improved (CRS change score = 5.8±5.4) when compared with the stable group (CRS change score = 3.0±6.5) (Table 3). Accordingly, it is also possible to verify that the proportion of changes related to initial values in CRS was higher in the improved group (CRS relative change = 37.9 ± 54.9%) than in the stable group (CRS relative change = 15.4 ± 31.5%). The results of the comparison between BL and FU scores validate the lack of significant changes in the stable group, as expected. Subgroups of change did not reveal equivalence on BL (stables = 27.9± 9.0 vs improved 2.00±6.7; P = 0.006) but the differences were non-significant on FU (P = 0.61).

Table 3

Responsiveness of CRS test to the 24 weeks-exercise program, considering groups of change in the CS test (stable and improved).

	CS stable group (N = 34)		CS improved group (N = 48)
Parameters	mean	± SD (median)	mean	± SD (median)	P value	ES (d)
CRS Baseline (x/30s)	27.8	± 9.0 (27,0)	22.0	± 6.7 (23.0)	0,00**	1.2†
CRS Follow up (x/30s)	30.8	± 9.1 (30,0)	27.8	± 6.5 (28.0)	NS	0.4
CRS Change score (x/30s)	3.0	± 6,5 (2.0) NS	5.8	± 5.4 (5.0)§	0.03*	0.6†
CRS relative change (%)	15.4	± 31.,5 (15.0)	37.9	± 54.,9 (32.0)	0.02*	0.5†

Means ± standard deviations (median) of CRS test results on baseline and follow up; change scores and relative change (%) in groups of participants classified as stable or improved (CS test change scores, MDC = 3.01).

*P<0.05,

**P<0.001, comparison between groups (T-Student or Mann Whitney tests);

§P<0.001, comparison between baseline and follow-up scores (Wilcoxon test);

†ES |d |>0.5 (medium to high Effect Size, here considered as clinically relevant differences between group means); NS indicates non-significant differences.

Abbreviations: CRS = Calf-raise Senior test; CS = 30 s chair stand test.

A ROC curve analysis shows a change score in the CRS test greater than or equal to 3.5 reps has a sensitivity of 0.68 and specificity of 0.33. The area under the curve found in this test was 0.67 (P <0.01) indicating moderate discriminative ability.

Fig 1 shows the proportion of participants in the exercise program who had greater improvements in plantar-flexors (PF) strength and power than the MDC values (42.7%) and beyond MID (47.6%). Thirty five participants reached or overcame the MDC cut-off point of 4.6 and presented a mean CRS change score of 9.60 (± 4.33), while 37 elderly subjects improved PF function (≥ MID of 3.5) and revealed a CRS change score of 9.03 (± 4.45).

Fig 1

Means and standard deviations of change scores, and proportion of participants who reached or exceeded the MDC and MID cut-off points.

Discussion

This study aimed to test the responsiveness of CRS test, in a sample of older-adult participants undergoing a 24-weeks’ community exercise program.

The CRS test showed a small to moderate responsiveness. A higher responsiveness was found for the CS test both in this study, as well as in other studies [42].

The responsiveness of the CRS test was also performed using an external measure to compare changes and establish cut-off values associated with meaningful improvements in physical function as a result of the intervention. The comparative analysis of the CRS scores obtained in the two time points (BL and FU) between the groups of positive change (improved group) and without change (stable group) in the reference test (CS) revealed significant differences in absolute and relative changes. Considering that the attribute assessed in both tests is the same—strength in the lower limbs; and that the two tests are evaluated in a similar way—the number of movements performed in 30s (revealing the same limitations in cognitive and sensory terms); it seems reasonable to state that the CRS test is responsive to discriminate elderly subjects with relevant changes after an exercise intervention program.

The ROC curve analysis revealed an optimal cut-off point of 3.5 repetitions allowing us to establish the minimal important difference for the CRS test. With this analysis it was possible to identify about 70% of the participants who underwent a truly important change after the intervention, while recognizing approximately 30% of the elderly who did not show a real change in their strength in any of the methods. The MDC value revealed that a change score of 4.6 would be required for the resulting change in participant status to be outside the test error range, which is higher than the MID estimate. This is in accordance with other responsiveness studies, in which anchor-based approaches outweigh the values found in the distribution approaches [40,43], highlighting the difficulties in using the former method due to the lack of an optimal threshold which can accurately determine the cut-offs to set the MID. Therefore, if only the value of MID is considered to evaluate the effects of an intervention, the results may indicate that improvements can be attributed to test error and not necessarily to a true change. Moreover, if the MDC is used as the only reference of change, then a small but significant effect can be neglected [40]. Several authors state that the value of the MID may be related to the SEM, depending on the degree of improvement defined by the anchor [44,45]. It has been shown that a cut-off point for MID between "slightly improved" and "moderately improved" may be similar to 2.0–2.3 * SEM [34], while in studies requiring “moderate” or “much improvement”, MID corresponds to about 2.5–2.6 times the SEM value [34]. In the present study, the SEM value calculated for the CRS test was 2.8, indicating that the closest cut-off point of this relationship would be the MDC = 2.3 * SEM. In this case, the MID would be on the order of 1.25 * SEM, which is more in line with other studies [44] in which similar values using clinical parameters as the anchor were observed. Therefore, it is suggested that both values should be used in assessing ankle strength improvements resulting from an exercise program. In practice, we can establish that changes in CRS scores below 3.5 must be considered insufficient, values between 3.5 and 4.6 may be viewed as acceptable for slight to moderate changes (but with a chance of being inside the range of measurement errors), while scores above 4.6 can be considered as a true change.

The anchor-based approach used in the present study was based on an ecological perspective, considering that the effects of community programs are usually assessed through field tests, which are easy to administer, have good acceptability and motivation, and reach a large number of participants in screenings [17]. Therefore, taking into account that the CS test is widely used in this context, and that it has been showing very positive indicators of validation, reliability and sensitivity to change in previous studies [19,46,29], its use seems to us acceptable for a preliminary approach in the scope of CRS test responsiveness assessment. Nonetheless, to indicate a true change in the plantar-flexors strength, a comparison with a quantitative direct measures as gold-standard measures would be more accurate, such as a dynamometer strength test, force platform, a biomechanical gait analysis, or the use of other specific clinical test for ankle strength assessment (e.g. manual muscle testing) [47].

The lack of other studies assessing CRS responsiveness prevents comparison of the results found in the present study. As suggested by Revicki [48], the estimate of MID should be confirmed through on the accumulation of evidence from several studies, in order to build greater confidence in the defined cut-offs values. Therefore, it is necessary to develop further studies using a larger sample composed of participants with higher / lower functional-fitness levels, as well as performing interventions that address longer-term changes in physical function. We also suggest carrying out additional research to evaluate whether the test can detect relevant changes in people with a higher baseline physical condition since the sensitivity to change demonstrated by the CRS test was more evident in groups of subjects with lower initial scores. Despite the weaknesses identified, this is the first article that defines the responsiveness of the CRS test, identifying cut-off values of MDC and MID that may help to establish a basis for future studies focused on plantar flexion strength and power interventions in the elderly.

Conclusions

This study aimed to examine the responsiveness of the Calf-Raise Senior (CRS) test through a 24-week exercise intervention designed to improve muscle strength, endurance, flexibility and balance, as key factors affecting physical function.

The results strengthen the psychometric properties of CRS, revealing its ability to detect change after a 24 week community exercise program focused on improving functional mobility in the elderly. In addition to its excellent validity, reliability, and acceptability by participants and professionals, the CRS test revealed good responsiveness in detecting changes in plantar flexion function over time. The present study also provides data relevant to the field application of these measures, reporting cutoffs of 3.5 and 4.6 for the MDC and MID estimates, respectively.

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3 Jan 2020

PONE-D-19-31500

Responsiveness of the Calf-Raise Senior Test in community-dwelling older adults undergoing an exercise intervention program

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Reviewer #1: Congratulation to the technically sound article.

Please let the article be reviewed by a native speaker. There are to many language errors (especially singular/plural) included making it hard to follow in some passages.

Once this adjustions and the following remarks are handled I'm optimistic, that the article might meet the criterias for publication.

Abstract.:

, which are particularly relevant in mobility -> redundant. remove.

in order to detecting improvements -> grammar

assessed with CRS -> introduce abbreviation in Abstract Line 4 and first occurence in main text and in conclusion

change measures of changes-> change-measures

using -> how? Difference among both scores?

Extended version in Abstract: Effect size (ES, Standardized response mean (SRM, Minimal Detectable Change (MDC

L2: in the last decades -> delete

L25-L26: Among these, few. -> reframe the sentence (few already in the previous sentence)

L28: and “Timed Up and Go” -> and the “Timed Up and Go” test

L31: , which was already been mentioned as having great significance -> , as beeing relevant

L37: then -> delete + the whole sentence must be rewritten

L37: responsiveness it’s not yet been -> awkward

L37: of CRS test, -> of the CRS test,

L51: is described elsewhere [31]. -> A... can be found in ...

Please make all related articles available with the next submission for review purposes. [31]

L83: a health and falls assessment questionnaire designed is there a english speaking representative questionair availebe`? Than please name this as well for orientation

L88: 30-seconds chair stand test (CS) -> unify names among paper based on the naming version in introduction

L89: "The CRS test was developed to evaluate ankle muscle function in older adults and had shown to have an excellent test-retest reliability (ICC = 0.90), inter-rater reliability (ICC = 0.93-0.96) and a good intra-rater agreement (ICC = 0.79-0.84) [24, 25]. It also presented a significant association between their scores and laboratory strength assessments (isometric, r = 0.87, r2 = 0.75; isokinetic, r = 0.86, r2 = 0.74; and rate of force development, r = 0.77, r2 = 0.59), demonstrating to be an excellent indicator of ankle strength in older adults [25]. The CRS test protocol is fully described elsewhere [25]. Briefly, the test includes the performance of a maximum number of heel lifting / lowering repetitions in the standing position, in 30 seconds, with the knees extended, at maximum possible range and velocity, without transferring the body weight to the hands. The test score corresponded to the number of cycles correctly executed at the end of 30 seconds. " -> Move to intro

L100: "The CS test is considered as a good indicator of mobility and has shown to predict the functional decline and risk of falls in the elderly [18, 34]. This test aims at evaluating functional strength of the lower limbs in older adults [33-36] and was chosen as an external reference measure (anchor) in this study since it measures the same attribute of CRS: lower limbs strength. In addition, having an excellent criterion validity, confirmed through a strong correlation with maximum voluntary contraction in the lower limbs (r = 0.77, 95% CI = 0.64-0.85) and an effect size of 0.83 when comparing elderly with high vs. low level of physical activity (P < 0.001), this test has also demonstrated an excellent test-retest reliability (r = 0.89, 95% CI = 0.79-0.93) [19]. The CS protocol consists of the performance of the maximum possible repetitions of the stand/ sits down movements in 30 seconds [37, 38]." -> Move to intro and adjust surrounding texts to fit again

L79: Assessments

Here it might be great to have some extra details regarding the intervention. In this case aklter the Sectiontitle correspondingly

L41: Didn't you included a control group? Just all 61 in one group? Please clarify and state in text. In that case, you can only confirm to measure a change. Its not confirmable that you have a stable base measure, which would b a pitty :)

L122: data at BL and FU within groups. -> groups?

L126ff: The methods in the following Lines must be described super-precise (eventually even formulars if not common known ones)

L130: "These approaches have 131 advantages and limitations, and some authors advise both, in order to provide a most complete 132 and comprehensive information of changes [39, 40, 42]. -> IMO: not relevant for Methods. Ratehr intro in case ...

L133: change scores of -> reframe

L148: important to be considered as “true 149 changes” [49]. -> Please clarify the approach name when a a true change was found. Which conditions must be given in that case, etc...

L151: I might have missed, but where have you explained how to separate these groups?: "between groups of participants with positive change (improved) versus no change (stable) [39, 50].""

L154 / L90: Its challenging that you are using two different ICCs within this study. This must be clearly discussed and reasoned.

L240: The ROC curves analysis revealed an optimal cut-off point of 3.5 repetitions as a change score -> of whoch assessment?

L220: which was lower than -> which was less distinct than

L244: who did not have a real change in their strength. -> who did not have shown a real change in their strength in any of the methods.

L255 : between "slightly improved" and "moderately improved" may be similar to 2.0-2.3 * SEM, -> Cite a corresponding reference

**********

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17 Feb 2020

“Congratulation to the technically sound article.

Please let the article be reviewed by a native speaker. There are to many language errors (especially singular/plural) included making it hard to follow in some passages.

Once this adjustions and the following remarks are handled I'm optimistic, that the article might meet the criterias for publication.”

Author response: We found your comments extremely helpful and have revised accordingly. All spelling and grammatical errors pointed out by the reviewer have been corrected in the text.

Abstract:

1) which are particularly relevant in mobility -> redundant. remove.

Author response: Agree. We have modified, accordingly.

2) in order to detecting improvements -> grammar

Author response: Agree. We have modified, accordingly (line 2)

.

3) assessed with CRS -> introduce abbreviation in Abstract Line 4 and first occurence in main text and in conclusion

Author response: We agree with this and have incorporated your suggestion throughout the abstract (lines 5 and 9).

4) change measures of changes-> change-measures

Author response: Agree. We have modified, accordingly (line 10).

5) using -> how? Difference among both scores?

Author response: We have modified the text to make it clearer (lines 10-11).

6) Extended version in Abstract: Effect size (ES, Standardized response mean (SRM, Minimal Detectable Change (MDC

Author response: Agree. We have incorporated your suggestion throughout the abstract (lines 13, 14, 18).

Introduction

1) L2: in the last decades -> delete

Author response: Agree. We have modified, accordingly (line 29)

2) L25-L26: Among these, few. -> reframe the sentence (few already in the previous sentence)

Author response: Thank you for pointing this out. We have modified the text to make the sentence clearer (lines 56-60).

3) L28: and “Timed Up and Go” -> and the “Timed Up and Go” test

Author response: Agree. We have modified, accordingly (line 61)

4) L31: , which was already been mentioned as having great significance -> , as beeing relevant

Author response: Agree. We have modified, accordingly (line 65)

5) L37: then -> delete + the whole sentence must be rewritten

Author response: We have modified the sentence to make it clearer (lines 75-81).

6) L37: responsiveness it’s not yet been -> awkward

7) L37: of CRS test, -> of the CRS test

Author response: Agree. We have modified, accordingly (line 74-76)

Materials and Methods

8) L51: is described elsewhere [31]. -> A... can be found in ...

Please make all related articles available with the next submission for review purposes. [31]

Author response: We have modified, as requested (lines 95-96). We also put the reference’s DOI in the bibliography section so that they can be consulted, if necessary.

9) L83: a health and falls assessment questionnaire designed is there a english speaking representative questionair availebe`? Than please name this as well for orientation

Author response: Thank you for your question. Unfortunately the English version of the QESQ questionnaire was not yet published as a journal article, but only as an abstract in a journal supplement (congress proceedings). It can be consulted trough the DOI:10.1249/01.mss.0000477095.65735.9c

10) L88: 30-seconds chair stand test (CS) -> unify names among paper based on the naming version in introduction

Author response: Agree. We have incorporated your suggestion throughout the article

11) L89: "The CRS test was developed to evaluate ankle muscle function in older adults and had shown to have an excellent test-retest reliability (ICC = 0.90), inter-rater reliability (ICC = 0.93-0.96) and a good intra-rater agreement (ICC = 0.79-0.84) [24, 25]. It also presented a significant association between their scores and laboratory strength assessments (isometric, r = 0.87, r2 = 0.75; isokinetic, r = 0.86, r2 = 0.74; and rate of force development, r = 0.77, r2 = 0.59), demonstrating to be an excellent indicator of ankle strength in older adults [25]. The CRS test protocol is fully described elsewhere [25]. Briefly, the test includes the performance of a maximum number of heel lifting / lowering repetitions in the standing position, in 30 seconds, with the knees extended, at maximum possible range and velocity, without transferring the body weight to the hands. The test score corresponded to the number of cycles correctly executed at the end of 30 seconds. " -> Move to intro

Author response: Thank you for pointing this out. We moved the first part of this sentence to the introduction section and have modified the surrounding text to make it clearer (lines 68-73). The second part of the sentence (underlined) was modified and maintained in this section in order to describe the CRS protocol together with the CS protocol for the readers (lines 155-160).

12) L100: "The CS test is considered as a good indicator of mobility and has shown to predict the functional decline and risk of falls in the elderly [18, 34]. This test aims at evaluating functional strength of the lower limbs in older adults [33-36] and was chosen as an external reference measure (anchor) in this study since it measures the same attribute of CRS: lower limbs strength. In addition, having an excellent criterion validity, confirmed through a strong correlation with maximum voluntary contraction in the lower limbs (r = 0.77, 95% CI = 0.64-0.85) and an effect size of 0.83 when comparing elderly with high vs. low level of physical activity (P < 0.001), this test has also demonstrated an excellent test-retest reliability (r = 0.89, 95% CI = 0.79-0.93) [19]. The CS protocol consists of the performance of the maximum possible repetitions of the stand/ sits down movements in 30 seconds [37, 38]." -> Move to intro and adjust surrounding texts to fit again

Author response: Thank you for this suggestion. We removed completely the first part of the sentence because we considered that it was cutting the flow of the text and did not add information that was relevant to the article. The second part of the sentence (underlined) was modified and maintained in this section in order to describe the CS protocol for readers (lines 150-155).

13) L79: Assessments. Here it might be great to have some extra details regarding the intervention. In this case aklter the Sectiontitle correspondingly

Author response: Thank you for pointing this out. Although we agree that this is an important consideration, we think that it not appropriate for inclusion in this manuscript because all information related to the intervention was described in detail in the referenced study, since it is a specific publication about the study protocol. We believe that the information provided in this manuscript can be sufficient to understand the results of the study. However, if you still feel that it is necessary to include more information about the intervention in this manuscript, we are available to change, accordingly.

14) L41: Didn't you included a control group? Just all 61 in one group? Please clarify and state in text. In that case, you can only confirm to measure a change. Its not confirmable that you have a stable base measure, which would b a pitty :)

Author response: You have raised an important aspect that can be pointed out as a potential limitation of the study, since the inexistence of control group did not allow the use of the Guyat’s index of responsiveness measure (Guyat G., 1987), which could strengthen the study. However, and considering the methodology of responsiveness analysis used, it is possible to state that this study was in line with most studies in this area, where the one-group design sample is usual. Responsiveness was demonstrated in this study both by distribution-based and anchor-based methods, which can be considered a strong point, as it allowed to confirm the test's responsiveness through different routes.

With regard to distribution-based analysis, according to authors such as Strand (2011) and Terwee (2007), the ability of an instrument to respond to change is mainly related to the minimally detectable change (MDC). This measure reflects the smallest change in a score that can be interpreted as a real change above the measurement error, and is dependent on the test-retest reliability of the instrument. In this case, we used the MDC values defined for the CRS and CS in previous test-retest reliability studies to verify whether the change score of the participants was above this measure, as an indication of real change.

Regarding the Anchor-Based Approach, we used the dichotomized scores of the CS as an external anchor of meaningful change. As referred by Strand (2011), ability of changes in scores on the physical tests to distinguish between participants who had improved, and those who did not have improved, can be analyzed using external standards of meaningful change by the receiver operating characteristic (ROC) curve. Thus, the stable measure in this study was considered as the group of participants who did not have improved their scores in CS test (anchor), considering the value of 3.01 for the change score.

We can naturally point out that this study would have achieved more robust results if a gold standard measure was used as an anchor, as mentioned in the limitations section. Likewise, the use of self-report questionnaires of functioning to identify the participants' perception of individual change in this parameter could add more information about the test's responsiveness.

Even so, we believe that our study complies with what would be necessary to affirm that the results found can be valuable to support the use of the CRS test in interventions with exercise for the elderly.

15) L122: data at BL and FU within groups. -> groups?

Author response: Thank you so much for catching this confusing sentence, which we have now been corrected. The sentence was moved from lines 166-169 to the end of the section (lines 228-229) because we realized that the methodology used to dichotomize the sample (improved vs. stable group) had not yet been explained at the beginning of the section, which could be confusing for the reader. We also removed information about correlations and comparisons between groups, as they were cutting the flow of text and did not add information that could be relevant to the article.

16) L126ff: The methods in the following Lines must be described super-precise (eventually even formulars if not common known ones)

Author response: We agree with this and changed the text to make it clearer, removing irrelevant parts and adding some extra information to facilitate the reader's understanding (lines 170-204).

17) L130: "These approaches have 131 advantages and limitations, and some authors advise both, in order to provide a most complete 132 and comprehensive information of changes [39, 40, 42]. -> IMO: not relevant for Methods. Ratehr intro in case ...

Author response: Thank you for this suggestion. We agreed that the text was not adding relevant information to the article and we removed the sentence completely.

18) L133: change scores of -> reframe

Author response: We agree. The text was completely changed in this part, as you suggested (lines 180-183).

19) L148: important to be considered as “true 149 changes” [49]. -> Please clarify the approach name when a a true change was found. Which conditions must be given in that case, etc...

Author response: Thank you for pointing this out. Extra information was added in the line 197 to clarify the sentence.

20) L151: I might have missed, but where have you explained how to separate these groups?: "between groups of participants with positive change (improved) versus no change (stable) [39, 50].""

Author response: We agree. The text was changed by including more information to provide a better comprehension about the methodology used (212-216).

21) L154 / L90: Its challenging that you are using two different ICCs within this study. This must be clearly discussed and reasoned.

Author response: Thank you for your suggestion. We changed the text accordingly, removing the ICC related to the previous study, so as not to confuse readers and facilitate their understanding (line 213).

22) L220: which was lower than -> which was less distinct than

Author response: We agreed that the sentence was not clear. Thanks for your suggestion, but we changed the text differently to facilitate the reader's understanding (lines 291-292).

23) L240: The ROC curves analysis revealed an optimal cut-off point of 3.5 repetitions as a change score -> of whoch assessment?

Author response: Thank you for your question. We agreed that the sentence was not clear and we changed the text provide a better comprehension of the method (lines 313-316)

24) L244: who did not have a real change in their strength. -> who did not have shown a real change in their strength in any of the methods.

Author response: Thank you for your suggestion. We changed the text accordingly (line 319)

25) L255 : between "slightly improved" and "moderately improved" may be similar to 2.0-2.3 * SEM, -> Cite a corresponding reference

Author response: Thank you for pointing this out. The reference was added to the line 332.

Additional clarifications

In addition to the above comments, all spelling and grammatical errors pointed out by the reviewers have been corrected.

We also introduced other changes to the article, which aimed to facilitate its understanding and prevent the reader's attention from being diverted. In this way, some parts of the text were removed, or had their structure changed, such as:

• Tables - were altered so that the data was displayed with only one decimal place, since in the previous format (two decimal places) it hindered the observation of the data;

• Lines 88-90 – sentence removed. We considered that it did not add relevant information to the manuscript;

• Lines 171-178 – most part of the text were removed. The feedback provided by the reviewer about this section allowed us to conclude that this part of the text was excessive and could lead the reader to not retain the desired information about the methodology used;

• Lines 303 to 312 – the first paragraph was moved to the lines 350-353 since we believed that it would be better framed as a limitation of the study. The second paragraph, in turn, we consider that did not make a great contribution to the discussion of the results, and in this way, it was eliminated.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

26 Mar 2020

Responsiveness of the Calf-Raise Senior Test in community-dwelling older adults undergoing an exercise intervention program

PONE-D-19-31500R1

Dear Dr. Andre,

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Additional Editor Comments (optional):

Reviewers' comments:

6 Apr 2020

PONE-D-19-31500R1

Responsiveness of the Calf-Raise Senior Test in community-dwelling older adults undergoing an exercise intervention program

Dear Dr. André:

I am 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 notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, 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.

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on behalf of

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Academic Editor

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