RESEARCH REPORT POSTER DISPLAY

NECK MUSCLE FATIGUE ON CHRONIC NECK PAIN WOMEN. Laliberté M¹, Larochelle J¹, Dumas J², Bilodeau M³, Arsenault B¹; ¹University of Montreal and CRIR-Montreal Rehabilitation Institute, Montreal (Qc), Canada. ²McGill University, School of Physical and Occupational Therapy, Montreal (Qc), Canada. ³University of Ottawa, School of Rehabilitation Sciences, Ottawa (Ont), Canada

PURPOSE: To determine if women with non traumatic chronic neck pain present increased fatigability of their neck extensor and flexor muscles as compared to healthy women. RELEVANCE: There is very little scientific data regarding the presence of superficial neck muscle fatigability in chronic neck pain patients. Also, studies on the matter present contradictory results. It would be important to understand the muscle impairments affecting the chronic neck pain sufferers in order to guide, with evidence based practice data, the clinicians in the rehabilitation process of their patients. PARTICIPANTS: Thirty women with bilateral non traumatic chronic (≥ 1 year) neck pain (CW) aged 31.1±8.3 years and 25 healthy women (HW) aged 33.0±8.5 years participated in this study. For the CW, mean score on the Neck Disability Index was 9.57±3.97. METHODS: For each subject, the maximal voluntary contraction (MVC) was first recorded in isometric neck flexion and extension (random order) in a sitting position. Then, the subject had to perform one 10s fatigue task at 75% MVC with a feedback given on a monitor. EMG signals were recorded with pairs of surface electrodes placed bilaterally on the splenius and sternocleidomastoid (SCM) muscles. Torque was measured in reference to C7-T1. The fatigue index used was the slope (Hz/s) of a series of EMG median frequencies (250 ms windows) over time during the task. ANALYSIS: Two way ANOVAs with repeated measures were used to compare the fatigue index between the two groups and within the both sides for a given muscle. A t-test was used to compare the strength between the two groups both in flexion and extension (alpha = 0.05). RESULTS: There was no difference between the MVC of the CW (15.46±5.00 Nm) and of the HW (17.10±6.53 Nm) groups in flexion. However, the CW (15.91±6.85 Nm) presented significantly less strength (19.61%) than the HW (19.79±6.26 Nm) in extension. For the splenius, even though the left splenius presented significantly more fatigability for both groups, no differences were found in the fatigue index between CW and HS (fatigue indices for the left splenius muscle: CW= −0.21±0.81 Hz/s; HW= −0.27±0.64 Hz/s). The interaction between the two factors was not significant. For the SCM, there were no differences in fatigue between the two groups and both sides. CONCLUSIONS: For the flexor muscles, the two groups had similar strength and levels of fatigue. For the extensor muscles, the CW had less strength than the HW. However, the two groups presented similar levels of fatigue of the extensors. The present results indicate that women with non-traumatic neck pain do not present increased fatigability at high load compared to healthy women. IMPLICATIONS: Based on the results of the present study, fatigability in superficial neck muscles of women with chronic non-traumatic neck pain cannot be considered as an impairment. KEYWORDS: Fatigue, neck muscles, EMG. FUNDING ACKNOWLEDGEMENTS: Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Ordre Professionnel de la Physiothérapie du Québec (OPPQ). CONTACT: recherche_cou@hotmail.com

ETHICS COMMITTEE: Ethics Committee of the Center for Interdisciplinary Researche in Rehabilitation of Greater Montreal (CRIR)