Kinesiophobia and its correlations with pain, proprioception, and functional performance among individuals with chronic neck pain.

Chronic neck pain (CNP) incidence in the general population is high and contributes to a significant health problem. Kinesiophobia (fear of pain to movement or re-injury) combined with emotions and physical variables may play a vital role in assessing and managing individuals with CNP. The study's objectives are 1) to evaluate the relationship between kinesiophobia, neck pain intensity, proprioception, and functional performance; 2) to determine if kinesiophobia predicts pain intensity, proprioception, and functional performance among CNP individuals. Sixty-four participants with CNP (mean age 54.31 ± 9.41) were recruited for this cross-sectional study. The following outcome measures were evaluated: Kinesiophobia using the Tampa Scale of Kinesiophobia (TSK), neck pain intensity using the visual analog scale (VAS), cervical proprioceptive joint position errors (in flexion, extension, and rotation directions) using cervical range of motion (CROM) device and handgrip strength as a measure of functional performance using the Baseline® hydraulic hand dynamometer. Kinesiophobia showed a strong positive correlation with neck pain intensity (r = 0.81, p<0.001), a mild to a moderate positive correlation with proprioception joint position errors (JPE) in extension, rotation left and right directions (p<0.05), but no correlation in flexion direction (p = 0.127). Also, there was a moderate negative correlation with handgrip strength (r = -0.65, p<0.001). Regression analysis proved that kinesiophobia was a significant predictor of pain intensity, proprioception, and functional performance (p<0.05). This study infers that kinesiophobia in individuals with CNP predicts pain, proprioception, and functional performance. Kinesiophobia assessment should be considered in regular clinical practice to understand the barriers that can influence rehabilitation outcomes in CNP individuals.

Introduction

In the general population, chronic neck pain (CNP) is one of the debilitating conditions that can impair the ability to perform regular everyday activities, decrease productivity, and adversely affect life quality [1]. In developed countries, approximately two-thirds of people experience neck pain [1]. At a given point in time, about 14% to 16% of the adult population globally experience neck pain [2], and the mean lifetime prevalence is 48.5% [2].

Chronic pain is categorized as pain that lasts more than three months [3]. However, there are distinct pathological mechanisms that contribute to the development of chronic musculoskeletal pain. It is critical to understand neuroplasticity (a neuron’s capacity to completely alter its structure, function, or biochemical profile in response to repeated afferent sensory inputs) to know how acute pain transforms as chronic pain [4]. Local inflammation of the injured tissue increases peripheral sensory neurons’ sensitivity (nociceptors), resulting in repetitive abnormal afferent input to the central nervous system [5]. Researchers also discovered that people with chronic pain have less volume in their prefrontal cortex—the part of the brain that controls thoughts, personality expression, and social behavior [6]. Chronic pain has been shown to induce escape and avoidance behaviors and is strongly associated with kinesiophobia [6, 7].

Kinesiophobia is a concept that describes a condition in which a patient has an unwarranted and deteriorating fear of physical movement and actions that results from a feeling of vulnerability to painful injury or re-injury [7]. An exaggerated negative cognitive and affective response to an anticipated or actual pain is expressed as pain catastrophizing [8]. It is characterized by an increase in the possible negative aspects of pain, an inability to disengage from stressful thinking, and a sense of helplessness in dealing with pain. In the acute pain stage, these habits may be adaptive [8]. However, in long-lasting pain, the issue paradoxically worsens, aggravating impairment and pain perception thresholds as patients enter a vicious cycle that perpetuates chronic pain and functional disability [9, 10].

CNP is multifactorial, and the factors that contribute to maintain and increase pain intensity are hard to define [11, 12]. A closed-loop, proprioceptive, vestibular, and visual systems’ interplay role works to maintain static and dynamic balance during functional tasks [11, 13]. Kinesiophobia and catastrophic behaviors can induce neck pain recurrence or cause changes in the somatosensory system [14]. The cervical afferent input to the higher centers may be changed by these changes, thereby impairing the cervical proprioception, which warrants assessment in detail [11]. Previous studies have shown that CNP individuals may be difficult or incapable of performing functional tasks [15, 16]. Also, kinesiophobia can further hinder their overall functional performance, which can affect their quality of life [17, 18]. Due to the avoidance of physical exercise, kinesiophobia may contribute to a deterioration of functional ability, leading to decreased mobility and chronic pain [18]. However, there is no conclusive evidence, how kinesiophobia impacts functional performance among individuals with CNP.

It is vital to develop effective recovery strategies in these neck pain patients by evaluating psychological factors before and after rehabilitation and recognizing which psychological impairments contribute significantly to neck rehabilitation [19]. There is no explored research, to our knowledge, in neck pain patients that correlated pain, proprioception and functional performance with kinesiophobia. The objectives of this study are 1) to evaluate the relationship between kinesiophobia, neck pain intensity, proprioception, and functional performance; 2) to determine whether kinesiophobia predicts pain intensity, proprioception, and functional performance among CNP individuals. We hypothesize that kinesiophobia is significantly associated with pain, proprioception, and functional performance. This study’s results may provide a fundamental understanding of the interactions between kinesiophobia, pain, proprioception, functional performance, and clinical management characteristics of kinesiophobia in CNP patients.

Material and methods

Design and settings

This cross-sectional study was conducted in the Department of Medical Rehabilitation, King Khalid University. The study followed the 1975 Declaration of Helsinki guidelines, as amended in 1983. King Khalid University ethics committee board (ECM#2019–61) approved this study. All the individuals read the patient information sheet, which included a concise summary of the research objectives and a detailed description of the research process and signed written consent before the study’s commencement. The individual pictured in Fig 1 has provided written informed consent to publish their image alongside the manuscript.

Fig 1

Cervical proprioception assessment using a cervical range of motion device.

Subjects

Sixty-four participants (38 males and 26 females) included in this study were over 18 years (age range: 28–64 years) and were referred to the physical therapy department by an orthopedist or general physician. Neck pain was defined as discomfort felt dorsally between the occiput’s (inferior margin) and T1. If they met the following inclusion criteria, CNP individuals were recruited: 1) neck pain for more than three months; 2) Chronic neck pain elicited by neck postures, neck movements, or palpation of the cervical musculature; 3) neck pain intensity of 30 to 70 mm measured on a visual analog scale (VAS); and 4) neck disability score, 15 or more measured on neck disability index (NDI). Exclusion criteria included: 1) signs of radiculopathy that were tested and confirmed by a positive Upper Limb Tissue Stress Test and Spurling Test [20]; 2) history of neurological disease or whiplash injury; 3) cervical myelopathy; 4) tumors; 5) cervical spine infection, and 6) insufficiency of the vertebrobasilar artery.

Sample size calculation

We used G*power 3.1 software (Universities, Dusseldorf, Germany) [21] to compute the study sample. As this study’s primary outcome, the Tempa scale of kinesiophobia (TSK) score (mean and standard deviation) was used to estimate the study sample [9]. The calculated sample size was 64, using a power of 0.80, an alpha of 0.05, and a beta of 0.2.

Outcome measures

Anthropometric data

Following the standard protocol, anthropometric characteristics were measured, including height (m), weight (kg), and BMI (kg/m2) (Table 1).

Table 1

Participant demographics, self-report measures, and study data (n = 64).

Variables	Mean ± SD (range)
Age (years)	54.31 ± 9.41 (28–64)
Gender (Male: Female)	38: 26
BMI (kg/m2)	25.60 ± 2.34 (21.4–26.1)
VAS (mm)	56.2 ± 0.98 (2.2–7.9)
NDI	19.65 ± 3.67
TSK total score	49.73 ± 11.82 (21–65)
Handgrip strength (kg)	21.06 ± 8.10 (5–38)
JPE
• Flexion	1.49 (2–8)
• Extension	1.14 (4–9)
• Rotation Left	1.391 (3–8)
• Rotation Right	5.16 ± 1.336 (3–8)

BMI = body mass index; VAS = visual analog scale; NDI = Neck Disability Index; TSK = Tampa scale of kinesiophobia; JPE = joint position error.

Kinesiophobia assessment

The Tampa Scale of Kinesiophobia (TSK) assessed the fear of movement or re-injury [22]. There was an appropriate degree of internal consistency in this questionnaire’s original versions (Cronbach’s alpha of 0.8), proof of prejudice, and parallel criterion-related and incremental validity [22]. The total TSK score ranges from 17 to 68, where 17 indicates no kinesiophobia, 68 shows moderate kinesiophobia, and ± 37 indicates that kinesiophobia is present [22].

Pain assessment

The current neck pain intensity was assessed using the visual analog scale (VAS) scores. The scale is 100 mm long and is anchored by the words "no pain" and "worst pain imaginable "on the left and right sides [23]. Individuals were requested to draw a vertical mark that better reflects the pain level across the horizontal line; 0–30 mm indicates mild, 30–70 mm indicates moderate, and > 70 mm indicates severe pain intensity. VAS is a widely used evaluation method and has good reliability and validity [24].

Proprioception testing

The Cervical Range of Motion (CROM) device (Performance Attainment Associates, Minnesota) was used to assess cervical spine range of motion (ROM) and proprioception. The CROM unit has three inclinometers and a magnetic yoke or harness (Fig 1). The individual in this manuscript has given written informed consent to publish these case details. The principles for joint position errors (JPE) measurements have been adopted by Alahmari et al. [25]. The JPE is estimated according to the participant’s capacity to consciously reposition his or her head to a target location previously shown by the examiner. Each individual was guided to the testing lab and got familiarized with the testing procedures. The individuals were asked to sit in the chair and put on the CROM device as if it were a pair of glasses, which was then secured around the head using the Velcro band (Fig 1). The individual in this manuscript has given written informed consent to publish these case details. A magnetic yoke was positioned directly over the participant’s shoulders and pointed north. The examiner used a webbing strap to minimize the patients’ shoulder and trunk motions during the examination. The examiner asked the individual to maintain the head in the neutral position (starting point) and standardized the CROM device to the starting position.

To start with JPE testing, the participants were asked to close their eyes throughout the testing procedure. The examiner slowly guided the participant’s head to the target position, which was previously determined and is 50% of their maximum ROM [13]. The participant’s head was then held in the target position for three seconds, allowing the individuals to memorize the target position. Successively, the examiner brought the participant’s head back to a starting position. The participant was then asked to reposition their heads to the target position consciously (absolute error). The examiner measured the relocation accuracy in degrees once they reached the reference position. The JPE testing was performed in four directions, i.e., flexion, extension, left rotation, and right rotation. A simple chit method was used to randomize the order of JPE testing in four directions [26]. Three attempts were performed in each movement direction, and an average of three attempts was used for analysis.

Functional performance

Handgrip strength as a measure of functional performance was measured using the Baseline® hydraulic hand dynamometer. It is a valid, clinically easy, useful test to measure grip strength [27] and identify any functional performance changes in individuals with CNP. This test is performed with the participant sitting in the chair with the shoulder adducted and neutrally rotated, elbow flexed to 90 degrees, forearm and wrist maintained in the neutral position (neither flexed nor extended), and gripping the handheld dynamometer (Fig 2) [28]. The individual in this manuscript has given written informed consent to publish these case details. The dynamometer was set to the second or third handle position to ensure consistency, claimed to be more suitable by the participant [29]. For most participants, the second position was used, which was considered the optimal level for grip evaluation and was adopted for routine testing by the American Society of Hand Therapists [29]. The individuals squeezed the handheld dynamometer’s handle as hard as possible, as explained by the investigator. The measurements were performed on the dominant side, three trials were conducted, and an average of three trials was used for analysis. The handgrip strength was recorded in kilograms. Between each attempt, a one-minute rest period was allowed to minimize fatigue effects. No verbal encouragement was to the participants during the handgrip strength measurements. The hydraulic hand dynamometer was calibrated regularly throughout the study duration.

Fig 2

Handgrip strength evaluation using a handheld dynamometer.

Statistical analysis

Descriptive demographic statistics, correlation, and regression analysis were performed using the IBM SPSS statistical software version 20 (IBM Corporation, USA). The significance of the study critical values was set at p < 0.05. Using the Shapiro-Wilks test, the normality of the study variables was analyzed. Pearson’s correlation coefficient was used to assess the relationship between kinesiophobia and pain, proprioception, and functional performance, and correlations were interpreted as follows: < 0.3 = mild, 0.31–6.9 = moderate, and ≥0.7 = strong. Furthermore, multivariate linear regression analysis was performed to determine whether kinesiophobia predicts pain, proprioception, and functional performance.

Results

Table 1 summarizes the demographic characteristics (age, BMI), pain intensity, proprioception JPE’s and physical performance (handgrip strength) values of the study population. Sixty-four CNP individuals participated in the study. The TSK score of this study’s participants was 49.73.

The correlations between kinesiophobia and neck pain intensity, proprioception, and functional performance are summarized in Table 2 and Fig 3. To our expectation, kinesiophobia showed a strong positive correlation with neck pain intensity (r = 0.81, p<0.001), a mild to moderate positive correlation with proprioception JPE errors in extension, rotation left and right directions (p<0.05), but no correlation in flexion direction (p = 0.127). Also, there was a moderate negative correlation with handgrip strength (r = -0.65, p<0.001).

Table 2

Relationship between kinesiophobia, pain intensity, functional performance, and proprioception (n = 64).

Correlated Variables	Kinesiophobia
	r	p value
Pain intensity (VAS)	0.81	<0.001
JPE
• Flexion	0.19	0.127
• Extension	0.48	<0.001
• Rotation Left	0.28	0.025
• Rotation Right	0.31	0.011
Handgrip strength (kg)	-0.65	<0.001

VAS = visual analog scale; JPE = joint position error. The correlation was tested using Pearson’s correlation coefficient analysis.

Fig 3

The relationship between kinesiophobia, pain intensity, functional performance, and proprioception JPEs in flexion, extension, left and right rotation.

(n = 64). VAS = Visual analog scale; TSK = Tempa scale of kinesiophobia; JPE = Joint position error.

Table 3 shows multivariate linear regression analysis findings between kinesiophobia, neck pain intensity, proprioception JPE and functional performance. Kinesiophobia was a significant predictor of neck pain intensity (r2 = 0.53, p<0.001), proprioception (extension: r2 = 0.12, p<0.002; rotation right: r2 = 0.09, p<0.008) and functional performance (r2 = 0.41, p<0.001) in individuals with CNP.

Table 3

Multivariate linear regression of TSK and explanatory variables (n = 64).

Variable	Adjusted R square	B	SE	p value
Pain intensity	0.53	0.73	0.01	<0.001
JPE
• Flexion	0.02	0.18	0.21
• Extension	0.12	0.37	0.15
• Rotation Left	0.04	0.23	0.20
• Rotation Right	0.09	0.33	1.18	0.008
Handgrip strength (kg)	0.41	-0.65	0.08	<0.001

JPE = joint position error; B = Standardized Coefficients Beta, SE = standard error.

Discussion

This study intended to establish the relationship between kinesiophobia, neck pain intensity, functional performance, and proprioception in CNP individuals. This study adds a crucial dimension to the findings of research on CNP individuals. The kinesiophobia showed a significant positive correlation with pain intensity and proprioceptive JPE’s and a significant negative correlation with handgrip strength. This study also showed that kinesiophobia significantly predicted neck pain intensity, cervical proprioception, and functional performance in individuals with CNP.

To the best of our knowledge, research assessing the association of kinesiophobia with pain intensity, cervical proprioception, and functional performance in populations with CNP is limited in the scientific literature. A previous study by Gunay et al. [30] showed no correlation between kinesiophobia and pain intensity in 87 non-specific CNP individuals. However, our study demonstrated a significant correlation between kinesiophobia and pain intensity. Compared to Gunay et al.’s study, our study participants had increased mean pain intensity (56.2 on VAS) and TSK score (59.73), which might have influenced these results. This study participants’ mean age was higher (54 years), and elderly individuals with CNP may show less resilience towards pain intensity and kinesiophobia [9]. Thus, this might explain the significant correlation between kinesiophobia and pain intensity in the study. The literature on kinesiophobia in other populations with chronic pain is more robust. Like this study’s results, Comachio et al. [31], using kinesiophobia in chronic back pain individuals, found a strong association between TSK scores and pain severity, disability, and quality of life [31]. Vaegter et al. [32], in an explorative analysis, showed a higher degree of kinesiophobia with increased pain intensity, and vice versa, in chronic musculoskeletal pain individuals [32].

This study showed a mild to moderate association between TSK scores and JPE’s in extension and rotation directions, fitting with our hypothesis, indicating that proprioceptive behavior is associated with fear of movement. The most direct inference on this finding may be that the cervical muscles’ proprioceptive functioning, considered the most significant afferent source of the neck, performing independently of its structure, and force-generating capabilities are influenced by fear of movement [11, 33]. There is a vicious cycle of maladaptive thoughts, leading to immobility with an increased perception of pain, leading to muscle atrophy and fibrosis, thus translating to functional disability [14]. During movements, kinesiophobia can also influence the altered activation patterns of neck muscles that may modify afferent input, leading to impaired proprioception [34]. In individuals with chronic low back pain, Pakzad et al. reported that pain catastrophizing was correlated with altered motor control and activation patterns [35]. Similar relationships may exist in CNP individuals.

Kinesiophobia induced by pain stimulation ultimately leads to fear avoidance behavior that can impact functional performance, including upper limb functions [9]. This study found a significant association between kinesiophobia and handgrip strength among individuals with CNP. A previous study [9] revealed that the crucial predictors of upper extremity function and disability significantly correlated with handgrip strength and kinesiophobia [9]. Bartlett et al. [36] showed a significant correlation between TSK scores, catastrophizing, disability, and comorbidity of musculoskeletal complaints in their investigation on individuals with neck and shoulder disorders [36]. The positive correlation in this study may be due to fear of movement. Long-term inhibition of upper extremity muscles may lead to disuse atrophy and translate to decreased handgrip strength [34].

Limitations

This study design was cross-sectional; therefore, causal relationships proving the presence of a temporal sequence between the exposure factor and the subsequent development of the disease cannot be identified. Cross-sectional research could, however, be performed as the first phase of a cohort study. This study limits the generalizability of our results, as this study included patients with moderate neck pain and disability. In this study, only absolute errors were recorded; constant and variable errors were not measured. The constant error and variable errors would have given more meaningful information regarding the direction and magnitude of errors in proprioception tests. Furthermore, confounding variables such as age, gender, nature of the job, marital status, formal education, smoking, sleeping hours, and leisure time (sport and hobby) that may have affected these findings were not considered by the authors. As a result, future studies should look at these confounding variables and see how they affect the outcome.

Conclusion

In conclusion, this study demonstrated that kinesiophobia significantly correlated with pain intensity, proprioception, and functional performance in CNP individuals. Also, kinesiophobia predicted pain, proprioception, and functional performance. Therefore, these correlations should be performed in clinical settings to understand and manage CNP individuals and further validate the current findings.

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30 Mar 2021

PONE-D-21-05740

Kinesiophobia and its correlations with pain, proprioception, and functional performance among subjects with chronic neck pain

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Reviewer #1: The manuscript presented a study aimed to evaluate the relationship between kinesiophobia, pain, proprioception and functional performance among subjects with chronic neck pain. The influence of kinesiophobia in the musculoskeletal rehabilitation is well understood in the previous studies, however, the authors justified that limited studies have been done among people with CNP. Generally, the paper was written with a good flow, A few comments for improvement is suggested prior to publication:

1. Revise the title, may need to change the term subjects. Also be consistent in the paper either to use subjects or participants.

2. In the introduction, it was not clearly explained which one comes first, pain or kinesiophobia or vice versa. As it is clearly stated in the previous literature pain is the cause of impairment. This needs to be clearly discussed.

3. In the Methodology; some outcome measures were not well described in terms of its procedure, so that it is replicable.

4. In the results: The authors have not considered any confounding factors such as duration of condition, nature of job, etc.

5. Others: i. Some typo errors were noted, need to check for English as well.

Reviewer #2: In the current manuscript, authors have investigated the “Kinesiophobia and its correlations with pain, proprioception, and functional performance among subjects with chronic neck pain”. It is a very interesting study, but I strongly encourage the authors to edit their paper with someone who has professional proficiency in English. In some parts, I had some difficulty to understand what the authors are trying to communicate.

Reviewer Comments:

Title: Change the “subjects” to “individuals”

Introduction and discussion need to be written again and consider adding more up to date references. You can use key words like “neck pain and upper limb proprioception” in your literature review researches.

Methods:

• What is “patient information sheet”? Is it study procedure or any type of questionnaires?

• My suggestion is to change the subjects to participants for the entire of the manuscript

• What was the age range? You just mentioned: “All the participants included in this study were over 18 years and ...” for example you should say (18-50 years)

• In addition, say how many male and female were participated in your study.

• Page 6: “1) Subjects diagnosed with CNP and pain subsequently felt between the first thoracic spinal process and the occiput's lower margin” how did you diagnosed that?

• Page 6: “2) neck pain intensity of 30 to 7o mm measured on a visual analog scale (VAS).” Fix the number 70 and clarify why you choose this intensity?

• Page6: “3) moderate neck disability score, between 15 to 30 measured on neck disability index” according to the NDI scoring your value should be between 15 - 24 to be consider a moderate neck pain. Check the following website (https://chiro.org/LINKS/OUTCOME/Painter_1.shtml)

• For sample size calculation what was your rational to use Tempa scale of kinesiophobia (TSK) score to estimate the study sample.

• Page 7: for the Anthropometric Data, refer to the table that has these information

• Page 7? Why you have the results for the Kinesiophobia Assessment but you did not included the results for Pain assessment

• Page 8: you should explain here what is your rational for choosing (50 % of their maximum ROM)

• Page 8: did you only analysis the absolute error? How about constant and variable errors?

• Functional Performance need to be more clarified. For how long they hold the dynamometer. What do you mean with neutral position? What was the position of the shoulder? What do you meand with dominant side> Right hand or left hand? Why you chose the highest value for analysis? Why you din not average the trials? How many trials they did? Why one minute rest? You should explain all the procedure and rational of your work in here.

• Change the title of table 1 to “Participant demographics, self-report measures, and study data”

• Page 10 “Kinesiophobia showed a positive mild to a moderate positive correlation with proprioception JPE errors in extension” there is two positives

• You should add more information on how to use the CROM

• Improve your JEP section

section

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Reviewer #1: Yes: Associate Professor Dr Maria Justine

Reviewer #2: No

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22 Apr 2021

Thank you for your effort and time in reviewing our manuscript. The reviewing process has significantly improved the quality of this manuscript. I am submitting this "Response to reviewers" document summarizing the changes that we made in response to the critiques.

RESPONSE TO REVIEWR 1

1. 1. Revise the title, may need to change the term subjects. Also be consistent in the paper either to use subjects or participants.

Answer• The term “subjects” was replaced with “individuals.” The changes are implemented throughout the manuscript.

2. 2. In the introduction, it was not clearly explained which one comes first, pain or kinesiophobia or vice versa. As it is clearly stated in the previous literature pain is the cause of impairment. This needs to be clearly discussed.

Answer• I agree with your statement that pain comes first, and it is the cause of impairment. • The introduction is modified.

3. 3. In the Methodology; some outcome measures were not well described in terms of its procedure, so that it is replicable.

Answer• The outcome measures are described in detail to replicate the study procedure.

4. 4. In the results: The authors have not considered any confounding factors such as duration of condition, nature of job, etc. A

h as duration of the condition, nature of the job, etc., were not considered, as these were not the objectives of this study, but as you say, these can be the confounding factors.

• The same is mentioned as a part of the limitations of this study.

5. 5. Others: i. Some typo errors were noted, need to check for English as well.

Answer• Professional English experts have edited the manuscript to fix the grammatical issues.

RESPONSE TO REVIEWR 2

1. Reviewer #2: In the current manuscript, authors have investigated the “Kinesiophobia and its correlations with pain, proprioception, and functional performance among subjects with chronic neck pain”. It is a very interesting study, but I strongly encourage the authors to edit their paper with someone who has professional proficiency in English. In some parts, I had some difficulty to understand what the authors are trying to communicate.

Answer• Professional English editing experts have edited the manuscript.

2. Reviewer Comments:

Title: Change the “subjects” to “individuals”

Answer• The term “subjects” was replaced with “individuals.” The changes are implemented throughout the manuscript.

3. Introduction and discussion - consider adding more up to date references. You can use key words like “neck pain and upper limb proprioception” in your literature review researches.

Answer• The introduction and discussion rewritten and added with more up-to-date references.

4. Methods:

• What is “patient information sheet”? Is it study procedure or any type of questionnaires?

Answer• The information sheet included a concise summary of the research project and its objectives and a detailed description of the research process. It defined what participation entails in practice, how long it takes, where it occurs, and what it entails.

5. • My suggestion is to change the subjects to participants for the entire of the manuscript

Answer• The term “subjects” was replaced with “individuals.” The changes are implemented throughout the manuscript.

6. • What was the age range? You just mentioned: “All the participants included in this study were over 18 years and ...” for example you should say (18-50 years)

Answer• All the participants included in this study were over 18 years (age range 18 to 64 years). • Changes are incorporated in the manuscript.

7. • In addition, say how many male and female were participated in your study.

Answer• No. of male and females participated in this study are mentioned in the text and in table 1.

8. • Page 6: “1) Subjects diagnosed with CNP and pain subsequently felt between the first thoracic spinal process and the occiput's lower margin” how did you diagnosed that?

Answer• I mean to say that subjects are diagnosed with neck pain by the orthopaedician, neurosurgeon, or general physician and

• Neck pain was defined as pain felt dorsally between the inferior margin of the occiput and T1.

• The confusing statement is modified.

9. • Page 6: “2) neck pain intensity of 30 to 7o mm measured on a visual analog scale (VAS).” Fix the number 70 and clarify why you choose this intensity?

Answer• We included neck pain intensity of 30 to 70 mm measured on a visual analog scale (VAS) as we want to make sure all the subjects had mild to moderate neck pain intensity levels.

• Previous studies also have used similar inclusion criteria -Lauche, R., Langhorst, J., Dobos, G. J., & Cramer, H. (2013). Clinically meaningful differences in pain, disability and quality of life for chronic nonspecific neck pain–a reanalysis of 4 randomized controlled trials of cupping therapy. Complementary therapies in medicine, 21(4), 342-347.

• Number 70 is fixed.

• Changes are incorporated in the manuscript.

10. • Page6: “3) moderate neck disability score, between 15 to 30 measured on neck disability index” according to the NDI scoring your value should be between 15 - 24 to be consider a moderate neck pain. Check the following website (https://chiro.org/LINKS/OUTCOME/Painter_1.shtml)

Answer • I agree with you that according to the NDI scoring, the value should be between 15 - 24 to be considered a moderate neck pain

• There is a Typo error. We included subjects with NDI score of 15 or above.

• The changes are incorporated in the manuscript.

11. • For sample size calculation what was your rational to use Tempa scale of kinesiophobia (TSK) score to estimate the study sample.

Answer• We selected the most important parameter (i.e., TSK score) in the study and computed the sample size required for it. The rest of the parameters were not able to provide enough precision.

• We computed the sample size separately for each parameter in the study and used the greatest obtained sample size i.e., TSK score.

12. • Page 7: for the Anthropometric Data, refer to the table that has these information

Answer• The changes are incorporated.

• referred to Table 1 for information

13. • Page 8: you should explain here what is your rational for choosing (50 % of their maximum ROM)

Answer• The tests were conducted in midranges (50 % of their maximum ROM) and therefore not engaging the joint receptors as limit detectors, highlighting the emphasis of tests for muscle spindle afferent activity.

• Reference: Hillier, Susan, Maarten Immink, and Dominic Thewlis. "Assessing proprioception: a systematic review of possibilities." Neurorehabilitation and neural repair 29.10 (2015): 933-949.

• The cervical JPE measurement protocol was adopted from Alahamrirt et al. study. This study also used 50% of the maximum range of motion as target head position.

• (Alahmari, Khalid, et al. "Intra-and inter-rater reliability of neutral head position and target head position tests in patients with and without neck pain." Brazilian journal of physical therapy 21.4 (2017): 259-267.)

14. • Page 8: did you only analysis the absolute error? How about constant and variable errors? • In this study, only absolute errors were recorded; constant and variable errors were not measured.

• The same has been mentioned as one of the limitations of this study.

15. • Functional Performance need to be more clarified. For how long they hold the dynamometer. What do you mean with neutral position? What was the position of the shoulder? What do you meand with dominant side> Right hand or left hand? How many trials they did? Why one minute rest? You should explain all the procedure and rational of your work in here.

Answer• The handgrip strength evaluation procedure is rewritten. This test is performed with the subject sitting in the chair with the shoulder adducted and neutrally rotated, elbow flexed to 90 degrees, forearm and wrist maintained in the neutral position (neither flexed nor extended) gripping the handheld dynamometer.

• The handgrip strength measurements were performed on the dominant side (mostly right hand), three trials were conducted, and an average of three attempts was used for data analysis.

• Between each attempt, a one-minute rest period was allowed to minimize fatigue effects. Previous studies also considered one-minute rest between trials, which was enough to eliminate the effects of fatigue. (Bobos, Pavlos, et al. "Measurement properties of the handgrip strength assessment: a systematic review with meta-analysis." Archives of physical medicine and rehabilitation 101.3 (2020): 553-565.)

16. • Change the title of table 1 to “Participant demographics, self-report measures, and study data”

Answer• Title of table 1 is changed to “Table 1. Participant demographics, self-report measures, and study data (𝑛 = 64).”

17. • Page 10 “Kinesiophobia showed a positive mild to a moderate positive correlation with proprioception JPE errors in extension” there is two positives

Answer• English editing of the article is done and the sentence is modified.

18. • You should add more information on how to use the CROM

Answer• Added more information on how to use CROM.

Submitted filename: Response to Reviewers.doc

Click here for additional data file.

11 May 2021

PONE-D-21-05740R1

Kinesiophobia and its correlations with pain, proprioception, and functional performance among subjects with chronic neck pain

PLOS ONE

Dear Dr. REDDY,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

You have mainly addressed the reviewers' concerns however However simply say that only absolute errors were recorded as a limitation is not acceptable. Constant and Variable errors can be calculated from the data that you have. There are many articles with the formulas. Here is one of many that explains how to calculate absolute, constant and variable error. https://motorcontrol.wordpress.com/2008/06/19/constant-error-variable-error-absolute-error-and-root-mean-square-error-labview/#:~:text=The%20formula%20for%20it%20is,alone%20without%20mentioning%20the%20direction.

Please include all error types in the methods, results and discussion of the next revision.

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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18 Jun 2021

· Thank you for sharing the link which showed the formulas to calculate the constant and variable error.

· We are unfortunate that we could not calculate the Constant and variable errors.

The formula to measure constant error is: Σ (xi-T)/N, and variable error is sq. root (Σ (xi-M)^2/N. In the formula "Xi" indicates the deviation from the target; it comes with a positive (overshooting) or negative sign (undershooting) that points out the error's direction. We did not measure or record this overshooting or undershooting. We measured the total error around the target (absolute error) only.

Submitted filename: Response to Reviewers.doc

Click here for additional data file.

24 Jun 2021

Kinesiophobia and its correlations with pain, proprioception, and functional performance among individuals with chronic neck pain

PONE-D-21-05740R2

Dear Dr. REDDY,

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Academic Editor

PLOS ONE

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Reviewers' comments:

28 Jun 2021

PONE-D-21-05740R2

Kinesiophobia and its correlations with pain, proprioception, and functional performance among individuals with chronic neck pain

Dear Dr. Reddy:

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on behalf of

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