Abstract
Abstract This study investigated neuromuscular activation strategies in individuals with different training backgrounds during isometric contractions of the knee extensor muscles (m. vastus lateralis) during moderate-intensity contractions (≤30% of maximal voluntary contraction, MVC) with progressively increasing load. Untrained (n = 18) and trained participants (n = 14) were compared. Muscle activity was recorded using high-density surface electromyography (HD-sEMG) during testing on an IsoMed 2000 isokinetic dynamometer, followed by signal decomposition and extraction of motor unit (MU) activation patterns. Analysis revealed differences in muscle activation strategies between groups: trained participants demonstrated a more economical MU recruitment strategy and more pronounced increases in MU discharge frequency and amplitude with rising load. The findings indicate that the greater efficiency of force generation in trained individuals is determined not only by higher absolute strength but also by functional adaptations in MU recruitment and discharge behavior. The results reflect specific neuromuscular adaptations formed in response to systematic strength training and may be useful for personalized assessment of the functional state of the neuromuscular system.