The Impact of Weekly Acceleration and Deceleration Loads on Neuromuscular Performance in Soccer: A Session-to-Session...

This study examined weekly variations in accelerations, decelerations, and neuromuscular performance in male under-19 soccer players. It also explored the relationship between accumulated acceleration and deceleration loads and fluctuations in neuromuscular performance across a weekly microcycle. A repeated-measures observational design was used over two consecutive weeks, involving 39 outfield players monitored via Global Navigation Satellite Systems. Neuromuscular performance was assessed through countermovement jump (CMJ), hamstring strength (HS), and delayed onset muscle soreness (DOMS), measured both before and after training on five days each week, following a consistent training structure. Significant post-training reductions in CMJ (all days p < 0.001) and HS (all days p < 0.001) were observed, with the greatest impairments occurring on MD-4 and MD-5, although CMJ showed a slight rebound on MD-5 compared to MD-4. DOMS ratings peaked on MD-3 (F = 39.186, p < 0.001), indicating a buildup of midweek fatigue. The highest numbers of accelerations (F = 248.121, p < 0.001) and decelerations (F = 227.853, p < 0.001) occurred on MD-4 and MD-5. However, no statistically significant correlations were found between daily acceleration/deceleration counts and changes in CMJ or HS performance. These findings suggest that while neuromuscular performance declines progressively throughout the week, no statistically significant correlations were found between impairments and the acceleration or deceleration load of individual training sessions. Instead, the cumulative effect and timing of high-intensity training may play a more substantial role in contributing to fatigue and neuromuscular decline.