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Table of Contents
ORIGINAL ARTICLE
Year : 2020  |  Volume : 2  |  Issue : 2  |  Page : 121-126

An observational pilot study to compare the strength and endurance of neck muscles of chronic neck pain patients as compared to age- and gender-matched controls using a handheld dynamometer


1 P.T. School and Center, TNMC and BYL Nair Hospital, Mumbai, Maharashtra, India
2 Department of Physiotherapy, TNMC and BYL Nair Hospital, Mumbai, Maharashtra, India

Date of Submission17-Mar-2020
Date of Decision06-Jun-2020
Date of Acceptance18-Jul-2020
Date of Web Publication04-Jan-2021

Correspondence Address:
Dr. Vaibhavi Bhupendra Rathod
A/3, Sahakar Darshan Society, Kisan Nagar 1, Wagle Estate, Thane - 400 604, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijptr.ijptr_6_20

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  Abstract 


Context: Neck pain is a common musculoskeletal disorder. Strength and endurance measurements of neck muscles can be of substantial help to evaluate the basic condition and examine whether the rehabilitation protocol has been beneficial or not.
Aims: The aim was to propose a technique to use handheld dynamometer for measurement of strength of neck muscles and study the strength and endurance of neck muscles in chronic nonspecific neck pain patients as compared to age- and gender-matched controls.
Settings and Design: It is a cross-sectional observational study.
Materials and Methodology: Neck muscle strength and endurance was measured in patients with neck pain (n = 30) and without neck pain (n = 30).
Statistical Analysis Used: Test–retest reliability, Man–Whitney U-test, and ratio analysis were used for statistical analysis.
Results: Inter-rater and intra-rater reliability for the technique used to measure neck muscle strength was found reliable and valid. The mean of neck flexor and extensor strength in neck pain patients was 2.97 ± 1.09 kg and 4.70 ± 0.87 kg (P < 0.05), respectively. The mean of neck flexor and extensor endurance in neck pain patients was 22 ± 12.21s and 52.57 ± 45.07s (P < 0.05), respectively. The ratio of the strength of neck extensors to neck flexors in neck pain patients was 2:1 and that of controls was 1.5:1.
Conclusions: Handheld dynamometer is a reliable tool to measure the strength of neck muscles. Strength and endurance of neck muscles chronic neck pain patients is significantly lower as compared to age- and gender-matched controls.

Keywords: Chronic neck pain, Handheld dynamometer, Muscle imbalance, Neck muscle endurance, Neck muscle strength


How to cite this article:
Asgaonkar BD, Rathod VB, Verma CV. An observational pilot study to compare the strength and endurance of neck muscles of chronic neck pain patients as compared to age- and gender-matched controls using a handheld dynamometer. Indian J Phys Ther Res 2020;2:121-6

How to cite this URL:
Asgaonkar BD, Rathod VB, Verma CV. An observational pilot study to compare the strength and endurance of neck muscles of chronic neck pain patients as compared to age- and gender-matched controls using a handheld dynamometer. Indian J Phys Ther Res [serial online] 2020 [cited 2021 Apr 14];2:121-6. Available from: https://www.ijptr.org/text.asp?2020/2/2/121/190045




  Introduction Top


Neck pain is a common musculoskeletal disorder that leads to significant disability throughout the world.[1],[2] Nearly two out of three individuals experience at least one episode of neck pain at some time during their lives.[3] A systematic review of different observational studies of neck pain around the world revealed that its annual prevalence ranged from 16.7% to 75.1% and a lifetime prevalence rate was 48.5%. Women are more likely to develop neck pain with an incidence rate ratio of 1.67 than men.[3] A prolonged forward head posture is commonly adopted by office workers, students, teachers, pilots of high-performance aircraft, surgeons, dentists, or people with an occupation of carrying heavy weights. Biomechanically, sustained forward flexion of the neck results in increased compressive loading on the cervical spine ultimately leading to imbalance of the neck muscles. This position places increased stress on the soft tissues and joints of cervical spine.[4]

Objective assessment of neck pain in the clinic usually includes measurement of the range of motion, palpation, and X-ray evaluation which are inadequate. A thorough assessment can be of substantial help to identify the cause of this problem so that appropriate preventive and therapeutic measure can be taken. Manual muscle testing can provide relative strength assessment and is not precise enough to monitor the progress of the patient who is on a strengthening program.

The purpose of the study is to find a simple, less time-consuming, and reliable method of measuring neck muscle strength using a Jamar hydraulic handheld dynamometer. The aim of the study is to compare the neck muscle strength and endurance of patients with chronic neck pain and healthy individuals without neck pain, so that appropriate therapeutic measures can be taken and incorporated in the rehabilitation program.


  Materials and Methodology Top


The present study was a cross-sectional observational study with convenient sampling. The study was endorsed by the Institutional Ethics Committee and was conducted at physiotherapy outpatient department (OPD). The study was conducted from December 2018 to May 2019. Since it was a pilot study, 30 participants were recruited in each of the groups.

The purpose of the study was explained and written informed consent was obtained from the participants. A total of 30 patients with neck pain and 30 controls with age- and gender-matched individuals were enrolled [Figure 1]. Inclusion criteria for neck pain patients were patients with nonspecific neck pain for more than 3 months, patients of both gender in the age group of 18–40 years, and patients willing to participate in the study. Exclusion criteria were radiating neck pain, patients rating pain on Visual Analog Scale more than 6,[5] past history of trauma to neck, cervical spine infection, history of cervical spine or shoulder surgery, congenital anomalies of cervical spine, progressive neurological disorder of cervical spine, and patients with rheumatoid arthritis.[6] Inclusion criteria for the control group were individuals without neck pain for more than 6 months and with a normal head neck alignment (plumb line should pass through the external auditory meatus and midway through the shoulder); Individuals who were age and gender matched with the study population whereas patients with improper head-neck posture, individuals with any history of neck pain within 6 months and vulnerable population (physiotherapy department students) were excluded from the study.
Figure 1: Schematic representation of methodology

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Each participant participated in a single testing session and was given the study information sheet. Data were obtained from the patients who came to OPD for the first time for treatment of neck pain. After data collection, the patients were further evaluated and treated for their respective condition.

Neck flexor and extensor strength was tested using a Jamar hydraulic handheld dynamometer [Figure 2].[7],[8] A Velcro strap was taken and an equidistant point was marked with the help of a marker and an equidistant point at the center of the dynamometer was marked. Center point of the dynamometer was placed on the center of the Velcro strap and then readings were taken to minimize subjective errors. Validity and reliability of the technique was checked by two authors at two different times where one author was masked of the result of the other.[9]
Figure 2: An equidistant point is marked on the Velcro strap and the point is placed on the center of the head and an equidistant point is marked on the dynamometer

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Measurement of neck flexor strength

All patients who participated in the study were asked to lie down in supine, crook lying position with elbows bent and hands overhead, resting on the plinth.[10] A Velcro strap (center point was marked with a marker) was put on their forehead such that center point of the strap comes exactly at the center of the forehead. An equidistant point was marked on the dynamometer such that it matched the center of their head to reduce subjective errors. They were asked to flex the cervical spine by lifting the head from the plinth, with chin depressed (chin tuck) and approximating toward the sternum.[10] The dynamometer was placed over the center of the forehead (center of Velcro strap), and resistance was applied on the anterior surface of the forehead in a posterior direction [Figure 3]. Participants were asked to hold the neck against the resistance applied by the tester (isometric work). Furthermore, they were instructed not to breathe hold in any of the techniques. Three readings were taken, and the best reading was considered as the neck flexor strength measured in kilograms.
Figure 3: Testing position of neck flexor strength

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Measurement of neck flexor endurance

For neck flexor endurance,[11] all the participants were asked to maximally retract the chin and maintain isometrically, they had to lift the head and neck until the head was approximately 2.5 cm off the plinth while keeping the chin retracted. A therapist focused on their neck and placed the hand below the occiput of the head. When the skin folds separated or their occiput touched the hand of the therapist, the test was terminated. Time up to which they were able to hold the position was recorded and considered as neck flexor endurance taken in seconds.[12]

Measurement of neck extensor strength

Neck extensor strength was also tested using a handheld dynamometer. Participants were asked to lie down prone with arms abducted and elbows bent and were asked to do chin up, i.e., neck extension.[10] Handheld dynamometer was placed on the center of their skull (center of the Velcro strap), and resistance was applied in the anterior direction [Figure 4]. They were asked to hold the neck against the resistance applied by the therapist (isometric work). Three readings were taken and the best reading was considered as the neck extensor strength measured in kilograms.
Figure 4: Testing position of neck extensor strength

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Measurement of neck extensor endurance

For neck extensor endurance,[13] participants were asked to hold the above-described position, i.e., neck in extension for as long as possible. Time up to they were able to hold the position was considered as neck extensor endurance taken in seconds.

Statistical analysis

Data were analyzed using the SPSS version 25 (Chicago, USA). Inter-rater and intra-rater reliability was tested using test–retest reliability. Descriptive analysis of the data was done. Since the data were not normally distributed, nonparametric test (Man–Whitney U test) was applied. The difference between the two means of neck flexor strength, neck extensor strength, neck flexor endurance, and neck extensor endurance of both the groups were compared using a Mann–Whitney U-test at 95% confidence interval with level of significance being 0.05. Ratio analysis was performed to compare the ratio of neck extensors to flexors in neck pain patients with controls.


  Results Top


The participants in both the groups were in the age group of 18–40 years, with a mean age of 30.33 ± 8.28 years. Inter-rater and intra-rater reliability for the technique used to measure neck flexor and extensor strength using a handheld dynamometer was found reliable and valid with an intraclass correlation coefficient of 0.87 and 0.85, respectively. The mean of neck flexor strength in neck pain patients was 2.97 ± 1.09 kg and age- and gender-matched controls was 4.87 ± 1.25 kg. The mean of neck extensor strength in neck pain patients was 4.70 ± 0.87 kg and healthy individuals was 6.87 ± 1.04 kg [Table 1] and [Figure 5]. The mean of neck flexor endurance in neck pain patients was 22 ± 12.21 s and age- and gender-matched controls was 69.90 ± 46.49 s. The mean of neck extensor endurance in neck pain patients was 52.57 ± 45.07 s and that of controls was 264.03 ± 119.22 s [Table 1] and [Figure 6]. Nonparametric test was used, i.e., the Mann–Whitney U-test, and a significant difference was found in all the four groups; the P value was significant at 95% confidence interval. The ratio of strength of neck extensors to neck flexors in neck pain patients was found to be 2:1 and for age- and gender-matched healthy individuals was 1.5:1 [Figure 7].
Figure 5: Mean of neck flexor and extensor strength of neck pain patients as compared to age- and gender-matched controls

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Figure 6: Mean of neck flexor and extensor endurance of neck pain patients as compared to age- and gender-matched controls

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Figure 7: The ratio of neck extensors to flexors is altered in neck pain patients as compared to age- and gender-matched controls

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Table 1: Comparison of neck muscle strength and endurance of neck pain patients with age- and gender-matched controls

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  Discussion Top


There was female preponderance in the present study, as neck pain is more common in females than in males. Females have a tendency to get neck pain more frequently than men which can be attributed to the kyphosed posture that females develop due to heavier upper body. A number of studies also found that women are more likely to experience neck pain than men with peak prevalence in middle age.[1],[2],[14],[15]

Pain leads to muscle inhibition which ultimately leads to weakness. Furthermore, pain may lead to muscular imbalances or impairment in posture causing the anterior neck muscles to go in weakness and posterior muscles into stretch weakness. Silverman et al. conducted a study that compared anterior cervical muscle strength in patients with neck pain and control patients, and they found that patients with neck pain had significantly less strength as compared to controls[16] A similar study conducted by Ylinen et al. found that the group with neck pain had lower neck muscle strength in all the directions tested than the control group.[17] There is no evidence that weakness is the consequence of pain or pain is the consequence of weakness. Neck muscle weakness can be a result of prolonged faulty posture which may cause decreased muscle strength and endurance. Jordan et al. found significant reductions in maximal isometric strength in both the neck flexors and extensors of neck pain patients, with the greatest reduction seen in the extensor muscle group.[18]

The neck flexor and extensor endurance in neck pain patients is significantly lower as compared to the control group because the decreased strength of the muscles will decrease the holding capacity of the muscle for longer period of time. Lee et al. conducted a similar study and found lower neck muscle endurance time with patients with neck pain.[19] However, some studies do not support these findings. Edmondston et al. found that patients with postural neck pain did not have significant impairment of neck muscle endurance compared to controls.[20]

Listug and Mitchell conducted a study to determine the extensor-flexor ratio for the neck musculature in normal participants and found that males' cervical strength averages revealed a 1.07:1.0 extensor-flexor ratio while females approximate a 1.47:1.0 ratio.[21] Hence, from the present study, it can be inferred that the ratio of neck extensors to flexors in neck pain patients is increased as compared to healthy individuals and it can be concluded that neck flexors are weaker as compared to neck extensors in neck pain patients. Therefore, during the rehabilitation program, neck flexors should be trained before the extensors.

Lack of instrumentation to assess isotonic contraction of neck muscles limited the study to only isometric measurements of neck muscles. A longitudinal study needs to be conducted, to understand, if weakness is the cause of neck pain, i.e., an individual who has weak neck muscles is more prone to neck pain in the long run or stronger muscles are protective against neck pain. For increasing the objectivity of the study, electromyographic analysis can be used.


  Conclusions Top


Handheld dynamometer is a reliable tool to measure the neck flexor and neck extensor strength. Strength and endurance of neck flexors and extensors of patients with chronic neck pain is significantly lower as compared to normal healthy individuals. The ratio of neck extensors to flexors in neck pain patients is increased as compared to controls, and hence, during the rehabilitation program, neck flexors should be trained before the extensors to avoid malalignment of muscles.

Acknowledgment

We would like to thank our Dean for allowing us to conduct our study in the institution premises. We would also like to specially acknowledge the participants for their valuable time and cooperation given for the study without whom this study would not have been possible. Special thanks to Ms. Danielle Dsouza for her valuable inputs and suggestions.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Arnold CM, Warkentin KD, Chilibeck PD, Magnus CR. The reliability and validity of handheld dynamometry for the measurement of lower-extremity muscle strength in older adults. J Strength Cond Res 2010;24:815-24.  Back to cited text no. 7
    
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Wani SK, Subrat S, Ostwal P, Quazi R. Prevalence of anterior head translation in patients with neck pain. Int J Curr Med Appl Sci 2016;9:78-83.  Back to cited text no. 12
    
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Parazza S, Vanti C, O'Reilly C, Villafañe JH, Tricás Moreno JM, Estébanez De Miguel E. The relationship between cervical flexor endurance, cervical extensor endurance, VAS, and disability in subjects with neck pain. Chiropr Man Therap 2014;22:10.  Back to cited text no. 13
    
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Ylinen J, Salo P, Nykänen M, Kautiainen H, Häkkinen A. Decreased isometric neck strength in women with chronic neck pain and the repeatability of neck strength measurements. Arch Phys Med Rehabil 2004;85:1303-8.  Back to cited text no. 17
    
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Lee H, Nicholson LL, Adams RD. Neck muscle endurance, self-report, and range of motion data from subjects with treated and untreated neck pain. J Manipulative Physiol Ther 2005;28:25-32.  Back to cited text no. 19
    
20.
Edmondston S, Björnsdóttir G, Pálsson T, Solgård H, Ussing K, Allison G. Endurance and fatigue characteristics of the neck flexor and extensor muscles during isometric tests in patients with postural neck pain. Man Ther 2011;16:332-8.  Back to cited text no. 20
    
21.
Listug A, Mitchell K. Cervical Isometric Extensor-Flexor Strength Ratios in Normal Subjects. Capstone; 2003. Available from: https://commons.pacificu.edu/work/a7f8fff4-3738-4854-9848-40259debc1be. [Last accessed on 2020 Jan 31].  Back to cited text no. 21
    


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