Acute bilateral experimental neck pain: Reorganise axioscapular and trunk muscle activity during slow resisted arm movements

Abstract

Abstract Aims Neck pain is frequent and many develop on-going neck pain after the initial onset. Studies on clinical neck pain suggested that altered axioscapular muscle activity may be an important factor in on-going neck pain. This study investigates the effect of bilateral experimental neck pain on axioscapular muscle activity during standardised resisted arm movements. Methods 25 healthy participants were recruited for this single blinded cross-over study. Experimental pain was induced by bilateral injection of hypertonic saline into the splenius capitis muscle. Isotonic saline was used as a control. Pain intensity was recorded using an electronic visual analogue scale (VAS; 0-10 cm). Participants performed standardised arm movements, from a seated position, while wearing 1 kg wrist weights. Six arm abduction movements (30° to frontal plane, 3 per side) were performed to an angle of 140°. Each movement consisted of two 3 s phases (up/down) and was separated by a 6 s break, before moving the opposite arm. Surface electromyography (EMG) was recoded from 8 bilateral muscles. Recordings were done before, immediately after, and 5 min after the experimental pain. Root-mean-square (RMS) of the EMG signals were extracted for each muscle and averaged for the 3 trials. Data was compared between sides and no differences were identified after which data was pooled for further analysis. Results During the painful condition for the slow upward movement, a reduced RMS-EMG activity was found for the ipsilateral upper trapezius (P< 0.01). In addition, increased RMS-EMG was found bilaterally for the erector spinae muscle (P< 0.01). Conclusion Bilateral experimental neck reorganise axioscapular and trunk muscle activity during resisted, slow upward movement. The results of this supports previous studies on neck pain patients suggesting neck pain is linked to axioscapular function and underpins the necessity to include the shoulder girdle in assessment and rehabilitation of neck pain patients.