Effects of a novel neck balance system on neuromuscular fatigue of neck muscles during repeated flexions and extensions

This study aimed at investigating the effects of a novel neck balance system (NBS), which is a baseball cap with counterweights in the occipital part, on neuromuscular fatigue of neck muscles during and after a full-range repeated neck flexion-extension task. Surface electromyography (sEMG) of sternocleidomastoid (SCM) and semispinalis capitis (SC) muscles was recorded in 15 healthy individuals during full-range flexion-extension movements of the neck lasting 5min at a fixed pace (1Hz), with or without NBS. Maximal isometric force and sEMG were recorded before and after the fatiguing task. During the fatiguing task, the SC muscle showed a higher decline in amplitude of sEMG with NBS than without NBS, while no differences in the SCM muscle emerged between the two conditions. Maximal isometric force of both neck flexor and extensor muscles decreased significantly after the fatiguing task, both with NBS (p<.05) and without NBS (p<.05), with no differences between the two conditions. In conclusion, adopting the NBS promotes an increase of the activation of neck extensor muscles, possibly leading to earlier decline of the neuromuscular performance and to diminished ability to actively stabilize neck structures. For these reasons, the adoption of the NBS during dynamic, fatiguing contractions may not be appropriate.