Rapid hamstrings/quadriceps strength capacity in professional soccer players with different conventional isokinetic muscle strength ratios

Abstract

Muscle strength imbalance can be an important factor in hamstrings muscle strain. A hamstrings/quadriceps (H/Q) strength ratio based on concentric peak torque values (H con:Q con) has traditionally been used to describe the potential for knee-joint destabilization. Because certain standard actions in soccer are explosive, the analysis of the H/Q strength ratio based on the rate of torque development (H rtd:Q rtd) might also be useful in the evaluation of joint stability. The objective of this study was to compare the H rtd:Q rtd between professional soccer players with heterogeneous values of H con:Q con. Thirty-nine professional soccer players took part in the following procedures on different days: 1) Familiarization session with the isokinetic dynamometer, and 2) Two maximal isometric actions and five maximal concentric actions at 60°·s-1 for hamstrings (H) and quadriceps (Q). Participants were ranked according to their H con:Q con ratio. The median third was excluded to form a high torque group (HTG), and a low torque group (LTG). Peak isometric (H) and concentric (H and Q) torques and rate of torque development (H) were significantly greater in the HTG group. Similarly, H con:Q con (0.68 ± 0.02 vs. 0.52 ± 0.03) and H rtd:Q rtd (0.54 ± 0.12 vs. 0.43 ± 0.16) were significantly greater in the HTG group than in the LTG group. There was no significant correlation between H con:Q con and H rtd:Q rtd. It can be concluded that H con:Q con and H rtd:Q rtd are determined, but not fully defined, by shared putative physiological mechanisms. Thus, the physiologic and clinical significance of H con:Q con and H rtd:Q rtd to an athlete's individual evaluation might be different. © Journal of Sports Science and Medicine (2012).