The effect of eccentric exercise-induced delayed onset neck muscle soreness on force steadiness and the spatial distribution of neck extensor muscle activity

This study investigated the effects of eccentric exercise-induced delayed onset muscle soreness (DOMS) on neck extensor muscle behaviour and force output, examining force steadiness and the spatial distribution of splenius capitis (SCap) and upper trapezius (UT) muscle activity. Twenty healthy individuals completed three laboratory sessions (baseline, 24 h and 48 h post-exercise), where participants performed submaximal isometric neck extension and flexion tasks (20%, 50%, and 70% of their maximum voluntary contraction). High-density surface electromyography was used to examine bilateral SCap and UT muscle activity, and force steadiness was evaluated using the absolute and relative amplitude of force fluctuations. Neck muscle soreness significantly increased 24 h and 48 h post-exercise compared with baseline (p < 0.001), along with significant reductions in pressure pain thresholds over suboccipital and C4 regions (p < 0.001). Caudal shifts of SCap and UT muscle activity were observed during neck extension contractions in the presence of DOMS (p < 0.01, p < 0.001, respectively), and entropy values were significantly higher at 24 h and 48 h for the SCap (p < 0.001). The absolute amplitude of force fluctuations during the neck extension contractions improved across sessions (p < 0.05). These findings suggest that acute neck muscle soreness induces a redistribution of neck muscle activity; this is likely to be adaptive to protect painful muscle regions.