Knee Extension Strength and Hamstrings-to-Quadriceps Imbalances in Elite Soccer Players

his study examined the relationship between hamstrings-to-quadriceps strength ratio ( H: Q) and relative strength of the knee extensors in elite soccer players. Peak torque was measured during isokinetic knee extension/ flexion at angular velocities of 60 degrees center dot s - 1, 180 degrees center dot s - 1 and 300 degrees center dot s - 1. 18 professional players were divided into 2 groups, depending on their H: Q at 60 degrees center dot s - 1. Players in the lower H: Q group ( n = 7) had significantly smaller H: Q ratios compared with the higher H: Q group ( n = 11) at all angular velocities ( 60 degrees center dot s - 1: 49.2 %; 95 % CI: 61.3- 57.8 % vs. 59.5 %; 95 % CI: 52.2- 46.2 %, p = 0.001). Players in the lower H: Q group had greater knee- extension peak torque compared with the higher H: Q group ( 60 degrees center dot s - 1: 313; 95 % CI: 335- 291 vs. 269; 95 % CI: 289- 250 N center dot m, p = 0.01). No differences were found in hamstrings' strength between the 2 groups ( 60 degrees center dot s - 1: 156; 95 % CI: 170- 143 vs. 160; 95 % CI: 173- 148 N center dot m, p = 0.96). Negative correlations between knee extension peak torque and H: Q ratio were observed at all angular velocities ( r = - 0.65 to - 0.67, p < 0.01). In conclusion, a low H: Q strength ratio measured during isokinetic strength testing in professional soccer players, is observed mainly in those with strong quadriceps muscles, while players with lower quadriceps strength have H: Q ratios around the recommended values.