Does muscle imbalance affect fatigue after soccer specific intermittent protocol?

ObjectivesThis study investigated the muscular strength imbalance dependence of the effect of fatigue induced by an exhaustive laboratory-based soccer-specific exercise on different hamstrings:quadriceps (H:Q) ratios of soccer players.DesignRepeated measures.MethodsTwenty-one male professional soccer players (23.2 ± 3.5 years) performed a pre-test to assess the concentric (con) and eccentric (ecc) strength of the knee extensors (KE) and flexors (KF) at 60° s−1 and 180° s−1. Then performed an exhaustive laboratory-based soccer-specific exercise and a post-test similar to the pre-test. The players were allocated into one of two groups in accordance to their conventional Hcon:Qcon (balanced group, BG = Hcon:Qcon > 0.60; unbalanced group, UNBG = Hcon:Qcon < 0.60).ResultsThe KEcon (BG = 4%, p < 0.05; UNBG = 6%, p < 0.01) and KFcon (BG = 7%, p < 0.01; UNBG = 8%, p < 0.01) at 60° s−1 were significantly reduced after exercise for both groups. However, KFecc at 180° s−1 was significantly reduced only in BG (16%, p < 0.01). The Hcon:Qcon and Hecc:Qcon were significantly reduced after exercise in BG (0.65 ± 0.03 vs. 0.62 ± 0.04, p < 0.05; 1.38 ± 0.2 vs. 1.20 ± 0.2, p < 0.01; respectively), but not in UNBG (0.55 ± 0.04 vs. 0.54 ± 0.07; 1.19 ± 0.1 vs. 1.13 ± 0.2, respectively).ConclusionsThe effect of fatigue induced by an exhaustive laboratory-based soccer-specific exercise on Hcon:Qcon and Hecc:Qcon in the dominant leg of professional soccer players is dependent on muscular strength balance. Thus, experimental designs and prevention programmes should consider that muscular strength balance might also module the game-induced fatigue of professional soccer players.