Abstract. BACKGROUND: People with neck pain often present with weakness in the scapulothoracic muscles. Few studies have examined lower trapezius (LT), middle trapezius (MT) and serratus anterior (SA) muscle strength in individuals with neck pain, nor compared strength to asymptomatic individuals. OBJECTIVES: The aim of this study was to examine LT, MT and SA muscle strength in individuals with chronic neck pain. METHODS: Descriptive cross sectional design. Twenty two individuals with chronic neck pain and 17 asymptomatic individuals were included. Participants were asked to complete a screening questionnaire, Neck Disability Index, and underwent manual muscle testing for the LT, MT, and SA muscles bilaterally. Data analyses included paired and comparative independent t-tests. RESULTS: For individuals with neck pain, significant within subject differences in strength between sides for the LT (P < 0.01) and MT (P < 0.01) were present. In contrast, no within subject difference between sides for the asymptomatic group was found for any muscle. Individuals with neck pain were significantly weaker than asymptomatic individuals for the LT (p = 0.02), MT (p = 0.03), and SA (p = 0.01) on their side of neck pain, but not on their non-painful side. CONCLUSIONS: Significant within subject differences were found between sides for the LT and MT while significant between group differences were identified for all three muscles tested.

Introduction: Scapulothoracic muscle weakness has been associated with neck pain (NP). Little evidence exists regarding lower trapezius (LT), middle trapezius (MT) and serratus anterior (SA) strength in this population. LT strength changes have been observed following thoracic manipulation in healthy subjects. The purpose of the present study was to examine scapulothoracic strength changes following cervical manipulation in subjects with NP. Methods: Twenty-two subjects with NP and 17 asymptomatic control (AC) subjects underwent strength testing of the LT, MT and SA using a hand-held dynamometer. Subjects with NP were treated with passive intervertebral neck manipulation and neck range of motion exercises. The AC group received no intervention. Strength testing was repeated after manipulation, then 48 and 96 hours later. Change scores were calculated for strength over time. Paired t-tests were done for strength change between painful and non-painful sides in the NP group. Independent t-tests were done for strength change between the NP group and AC group. Results: There was no significant difference between groups for age, gender, hand dominance or body mass index. Mean (standard deviation) symptom duration for subjects in the NP group was 43.27 (62.71) months. There was no significant difference in strength change over time between painful and non-painful sides in the NP group for any muscle; however, there was a significant difference in strength change over time between those in the NP group and AC group for the LT (p < 0.01), SA (p < 0.01) and MT (p < 0.01). Discussion: Scapulothoracic muscle strength improvements were observed in both extremities following passive intervertebral neck manipulation and neck range of motion exercises. Improvements lasted up to 96 hours following manipulation, even though no strengthening exercises were prescribed. Conclusions: Manipulation and range of motion should be considered as a component of intervention programmes for patients with NP and scapulothoracic muscle weakness. Future studies should compare manipulation alone to exercise alone to determine impact on strength.

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