Effects of Contrast Training Using Holding Isometric and Ballistic Exercises on Physical Performance of Youth Male Soccer Players: A Randomized Controlled Study.

This study aimed to compare the effects of a 12-week complex-contrast training (CT) intervention, combining both holding isometric and ballistic exercises, on the physical performance of male youth soccer players. Thirty (age: 17.7 ± 0.6 years) Tier 2 (developmental or trained) male soccer players were randomly assigned to the CT ( n = 15) or control group ( n = 15). Sprint force-velocity profile, 10- and 30-m sprint times, countermovement jump, change-of-direction speed, isometric mid-thigh pull, Yo-Yo intermittent recovery test level 1, kicking distance, and kicking velocity were collected at baseline and post-12-week intervention. A 2-by-2 mixed analysis of variance and analysis of covariance with the baseline scores as covariate and Bonferroni-corrected post hoc analysis revealed significant improvements in 10- and 30-m times, sprint Pmax (i.e., relative peak power), sprint ratio of forces for the first 10 m (i.e., average ratio of force for the first 10 m), change-of-direction speed, countermovement jump, isometric mid-thigh pull, kicking distance, and kicking velocity for the CT group compared with the control group ( p < 0.001-0.028, ηp2 = 0.18-0.56). The Yo-Yo intermittent recovery level 1 similarly improved in both groups. In contrast, no improvements were observed for maximal sprint velocity and slope of the linear decrease in the ratio of force as sprint velocity increases (i.e., the slope of linear decrease in ratio of force as sprint velocity increased). In conclusion, CT using holding isometric and ballistic exercises has the potential to induce neuromuscular adaptations and improve the physical performance of male youth soccer players. This CT method could be particularly relevant for soccer players without gym access and/or for nonresistance-trained players who may be reluctant to lift heavy weights.