Data

This randomized controlled trial investigated the effects of an 8-week, volume-equated eccentric training program comprising Nordic Hamstring and Reverse Nordic exercises performed either once or twice per week on physical fitness measures in pubertal male soccer players. A total of 34 participants were randomly assigned into a 1-day (n = 16; age = 14.58 ± 0.28 years) or 2-day (n = 18; age = 14.84 ± 0.22 years) per week training group. Physical fitness was assessed using 5 m and 10 m sprints, the 505 change of direction (CoD) speed test, Y-shaped agility test, countermovement jump (CMJ), and standing long jump (SLJ). Significant group-by-time interactions were observed for the 505 CoD test, agility, and CMJ performance (effect sizes [ES] = 0.80 to 1.13). However, no significant interactions were found for the 5 and 10 m sprint as well as SLJ (p > 0.05). Compared to the 1-day group, the 2-day training group showed greater improvements in CoD speed (∆7.36%; p < 0.001; ES = 0.92), agility (∆7.91%; p < 0.001; ES = 1.68), and CMJ (∆7.44%; p < 0.01; ES = 0.35), while no differences were observed in 5, and 10 m linear sprint or SLJ performance. According to individual response analysis, improvements across the physical fitness parameters beyond the smallest worthwhile change (SWC0.2) were observed in 22–83% of players in the 1-day group and 77–100% in the 2-day group. In summary, the findings suggest that when training volume is matched, distributing the eccentric training regimen over two days per week may lead to greater improvements in CoD speed, agility, and CMJ performance compared to a single-day approach.