Does muscle imbalance affect fatigue after soccer specific intermittent protocol?

This 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. Repeated measures. Twenty-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 H(con):Q(con) (balanced group, BG=H(con):Q(con)>0.60; unbalanced group, UNBG=H(con):Q(con)<0.60). The KE(con) (BG=4%, p<0.05; UNBG=6%, p<0.01) and KF(con) (BG=7%, p<0.01; UNBG=8%, p<0.01) at 60° s⁻¹ were significantly reduced after exercise for both groups. However, KF(ecc) at 180° s⁻¹ was significantly reduced only in BG (16%, p<0.01). The H(con):Q(con) and H(ecc):Q(con) 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). The effect of fatigue induced by an exhaustive laboratory-based soccer-specific exercise on H(con):Q(con) and H(ecc):Q(con) 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. Copyright © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.