The Effects of Short-Duration High-Intensity Soccer Fatigue Simulation on Dynamic Balance and Lower Limb Isokinetic Strength in Youth Soccer Players

Background. This study investigated the effects of short-duration high-intensity simulation of soccer fatigue on the dynamic balance and isokinetic strength of the lower limbs in youth soccer players. Methods. Thirty-nine youth soccer players completed a high-intensity fatigue simulation in 5-min. The participants performed tests on dynamic balance and isokinetic strength before the fatigue simulation (PRE), immediately after simulation (POSTS), and 20 min (POST20) and 35 min (POST35) after simulation. Dynamic balance was measured using the Y-Balance test for both legs in the anterior, posteromedial (PM), and posterolateral (PL) directions. The muscle strength of the lower limb was measured using the maximal isokinetic contraction of the dominant leg only. Results. Dynamic balance was significantly reduced after stimulation in all directions for both legs (P<0.005). Significant reduction in the eccentric hamstring, concentric hamstring, and concentric quadriceps peak torques were also observed (P<0.05). However, no significant reductions were found in the functional hamstring/quadriceps ratio and conventional hamstring/quadriceps ratio (P>0.05). Conclusion. Fatigue influences dynamic balance, hamstrings, and quadriceps strength which may have implications for higher risk of knee injury in youth players.