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

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 (Hcon:Qcon) 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 (Hrtd:Qrtd) might also be useful in the evaluation of joint stability. The objective of this study was to compare the Hrtd:Qrtd between professional soccer players with heterogeneous values of Hcon:Qcon. 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 Hcon:Qcon 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, Hcon:Qcon (0.68 ± 0.02 vs. 0.52 ± 0.03) and Hrtd:Qrtd (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 Hcon:Qcon and Hrtd:Qrtd. It can be concluded that Hcon:Qcon and Hrtd:Qrtd are determined, but not fully defined, by shared putative physiological mechanisms. Thus, the physiologic and clinical significance of Hcon:Qcon and Hrtd:Qrtd to an athlete's individual evaluation might be different. Key pointsSoccer players with high (0.66-0.70) and low (0.50-0.54) conventional concentric hamstrings:quadriceps ratios (Hcon:Qcon) tend to demonstrate similar profiles (i.e., high and low, respectively) in their rate of the torque development H/Q ratio (Hrtd:Qrtd).The lack of a significant relationship between Hcon:Qcon and Hrtd:Qrtd suggests that these ratios are determined, but not fully defined, by shared putative physiological mechanisms.Preseason screening programs that monitor hamstrings:quadriceps ratios should recognize that the physiologic and clinical significance of Hcon:Qcon and Hrfd:Qrfd to an athlete's individual evaluation might be different.