Neuromuscular Plantar Flexor Performance of Sprinters versus Physically Active Individuals

Introduction Comparison of the neuromuscular performance of different athlete types may give insight into the in vivo variability of these measures and their underpinning mechanisms. The study aims to compare the neuromuscular function of the plantar flexors of sprinters and physically active individuals to assess any differences in explosive force performance. Methods Neuromuscular performance of a group of sprinters (highly trained/national level, n = 12; elite/international level, n = 2) and physically active individuals (n = 14) were assessed during involuntary, explosive, and maximum voluntary isometric plantar flexions, across different muscle-tendon unit (MTU) lengths (10° plantarflexion, 0° (anatomical zero/neutral), and 10° dorsiflexion). Plantarflexion rate of torque development (RTD) was measured in three 50-ms time windows from their onset. The synchronous activation of the plantar flexor agonist muscles was calculated as the time difference between 1) the first and last muscle onset and 2) the onsets of the two gastrocnemii muscles. Muscle size and MTU stiffness were assessed using sonograms of the medial gastrocnemius and myotendinous junction. Results Sprinters exhibited greater involuntary RTD across time points (0-50 ms, 50-100 ms) and MTU lengths. In addition, sprinters demonstrated greater early phase voluntary RTD (0-50 ms, 50-100 ms) across MTU lengths. Sprinters also demonstrated greater late-phase RTD (100-150 ms), and relative maximal voluntary torque at the DF angle only. The sprinters demonstrated a more synchronous activation of the gastrocnemii muscles. There were no observable differences in muscle size and MTU stiffness between groups. Conclusions These findings suggest sprint-specific training could be a contributing factor toward improved explosive performance of the plantar flexors, particularly in the early phase of muscular contraction, evidenced by the greater explosive torque producing capabilities of sprinters.