Regional Distribution of Myoelectric Median Frequency in the Erector Spinae Muscles Under the Influence of Delayed-Onset Muscle Soreness.

Delayed-onset muscle soreness (DOMS) is a noninvasive pain model offering a unique opportunity to study trunk neuromuscular adaptations. While prior research has examined regional muscle activation in the lumbar region, the spatial distribution of median frequencies (MF) under DOMS has not been explored. This study investigated the effect of DOMS-induced pain on the spatial distribution of MF in the lumbar erector spinae muscles and its association with trunk force variability during submaximal contractions. Twenty healthy adults completed 2 laboratory sessions: 1 pain-free and 1 under low back DOMS. High-density surface electromyography was recorded bilaterally on the erector spinae during submaximal isometric trunk extensions. MF distribution was analyzed using centroid coordinates with and without DOMS. Force variability was also assessed. DOMS significantly increased perceived muscle pain and soreness in the lumbar region. It also caused a cranial and medial shift of the MF centroid, significant on 1 side of the trunk. However, force variability remained stable between conditions. These results suggest that DOMS induces regional adaptations in lumbar muscle MF. The spatial distribution of MF may serve as a novel and sensitive marker of neuromuscular adaptation to pain. The trunk system was able to maintain force steadiness despite pain and soreness.