A randomised controlled trial of 1- versus 2-day per week formats of Nordic hamstring training on explosive athletic tasks in prepubertal soccer players

Purpose: This randomised controlled trial examined the effect of volume-equated programmes of Nordic hamstring exercise (NHE) training, executed at frequencies of 1- or 2-days per week, on explosive athletic tasks (30 m sprint, 15 m manoeuvrability and standing long jump [SLJ]) in male youth soccer players (mean age: 10.3 ± 0.5 years). Materials and methods: Players were divided into an experimental group (n=31) which was further subdivided into 1-day (n=16) and 2-days (n=15) per week training conditions, and a control group (n=14). Results: There were significant group-by-time interactions for 30-m sprint (p<0.001, d=0.6), SLJ (p=0.001, d=1.27) and 15 m manoeuvrability (p<0.001, d=0.61). The experimental group demonstrated small to moderate effect sizes in 30-m sprint (d=0.42, p=0.077), SLJ (d=0.97, p<0.001) and 15 m manoeuvrability (d=0.61, p<0.001). The control group showed small significant performance decrements or no change in these variables. There were no significant differences between the 1-day and 2-day training groups. In two of the three tests (30 m sprint, SLJ) the 2-day group demonstrated larger effect sizes. Conclusion: The NHE enhances explosive athletic task performance in prepubertal youth soccer players and there may be only small advantages to spreading training over two days instead of one.