Ten weeks of isometric versus dynamic contrast resistance training on soccer players’ physical performance: a randomised controlled trial

Purpose The study aimed to compare the effects of high-load isometric versus high-load dynamic contrast resistance training on soccer players’ physical performance. Material and methods Highly trained male soccer players (<i></i>n = 105; aged 24.4 ± 3.3 years) were randomly allocated to a control (i.e., soccer training only; n = 35), high-load isometric training (<i>n</i> = 35), or high-load dynamic contrast resistance training (<i>n</i> = 35) group. Two intervention sessions were conducted weekly over 10 weeks during the off-season. Physical performance was assessed before and after the interventions for linear sprint speed (10 m and 40 m), change of direction speed, 300-yard shuttle run test time, countermovement jump height, standing long jump distance, and absolute and relative (to body mass) maximal strength (1RM squat). Results After the ANCOVA and post-hoc t-test, improvement was noted in the 10-m and 40-m sprints, and change of direction speed (<i>p</i> < 0.001–0.002) after both interventions compared to the controls. Further improvement was noted in the 300-yard shuttle run test time, countermovement jump height, and absolute and relative 1RM after dynamic compared to isometric intervention (<i>p</i> < 0.001–0.024). Conclusions High-load isometric and high-load dynamic contrast resistance training can improve soccer players’ physical performance (linear and change of direction speed), although the latter approach may induce greater improvement in the 300-yard shuttle run, vertical jump, and maximal dynamic strength.