The effect of therapeutic exercise on activation of the deep cervical flexor muscles in people with chronic neck pain
Deep cervical flexor muscle (DCF) activation is impaired with neck pain. This study investigated the effects of low load cranio-cervical flexion (C-CF) and neck flexor strengthening exercises on spatial and temporal characteristics of DCF activation during a neck movement task and a task challenging the neck's postural stability. Forty-six chronic neck pain subjects were randomly assigned to an exercise group and undertook a 6-week training program. Electromyographic (EMG) activity was recorded from the DCF, sternocleidomastoid (SCM) and anterior scalene (AS) muscles pre and post intervention during the cranio-cervical flexion test (CCFT) and during perturbations induced by rapid, unilateral shoulder flexion and extension. C-CF training increased DCF EMG amplitude and decreased SCM and AS EMG amplitude across all stages of the CCFT (all P<0.05). No change occurred in DCF EMG amplitude following strength training. There was no significant between group difference in pre-post intervention change in relative latency of DCF but a greater proportion of the C-CF group shortened the relative latency between the activation of the deltoid and the DCF during rapid arm movement compared to the strength group (P<0.05). Specific low load C-CF exercise changes spatial and temporal characteristics of DCF activation which may partially explain its efficacy in rehabilitation.