Low-volume Nordic hamstring training improves change-of-direction performance more than higher volumes in youth soccer players

Introduction Soccer players adopt hamstring-strengthening programs to enhance sprint and change-of-direction (CoD) performance, despite limited information on optimal volume. Therefore, we aimed to compare low, moderate, and high volumes of Nordic curl training on linear sprint and CoD in pubertal soccer players. Methods Sixty male youth soccer players (13.69 ± 0.31years, 159.43 ± 8.55 cm, 48.51 ± 7.93 kg) were randomly assigned into three groups: low- ( n = 20; 4 sets of 3 repetitions), moderate- ( n = 20; 4 sets of 6 repetitions), and high-volume Nordic curl training ( n = 20; 4 sets of 9 repetitions). The training program lasted 8 weeks in-season. Assessments of sprinting (10 and 20 meters) and CoD performance (15-m-dribbling test with and without a ball) were conducted before and after the intervention. Results While all three groups improved their performance across all tests, a two-way repeated-measures ANCOVA revealed a significant time × group interaction ( p = 0.012) for the 10 m linear sprint, with low- ( p = 0.022, d = 0.78) and moderate-volume ( p = 0.055, d = 0.71) Nordic curl training yielding better results than high-volume Nordic curl training. Nonsignificant between-group differences were encountered for the 20 m sprints. A significant time × group interaction was observed for the CoD without ( p = 0.002) and with the ball (CoDB, p = 0.014), with significantly better results for the low-volume Nordic curl training compared to moderate- (CoD, p = 0.012, d = 0.59; CoDB, p = 0.021, d = 0.60) and high-volume (CoD p = 0.004, d = 0.78; CoDB, p = 0.042, d = 0.56) Nordic curl training. Discussion Low-volume Nordic curl training is the most effective training dose for improving CoD performance in top-tier youth soccer athletes. For sprint, both low and moderate volumes improve the 10 m sprint more than high volume, and all three volumes improve the 20 m sprint similarly.