Dissociation between fatigued power output and traditional peak torque for isokinetic hamstring:quadriceps ratios in professional soccer players

Background Muscle strength imbalance assessment (e.g., hamstring-to-quadriceps ratio, H:Q) using traditional peak torque isokinetic measurements has been shown to be a weak risk factor predictor of future lower-limb injuries (e.g., hamstring strain and anterior cruciate ligament tear). In soccer, power-related tasks are commonplace and injuries are most likely to occur during fatigued high-velocity actions. Thus, it is reasonable to that calculating H:Q using power output and may serve as an alternative to traditional peak torque-based H:Q. Aims We aimed to investigate the relationship of isokinetic H:Q calculated from traditional peak torque and power output during non-fatigue and fatigue conditions. Methods Seventy-nine professional soccer players (25.6 +/- 4.9 years old; 78.7 +/- 8.1 kg; 179.4 +/- 6.7 cm) performed concentric knee extension-flexion contractions at 60 degrees(.)s(-1) (five repetitions) and 300 degrees(.)s(-1) (30 repetitions, fatigue trial). Traditional peak torque H:Q was calculated using the highest torque obtained during five repetitions at 60 degrees(.)s(-1). Power output H:Q(non-fatigued) was calculated using the average from the 2nd, 3rd and 4th repetitions, and power output H:Q(fatigued) was obtained as the average of the power output of the last three repetitions of the fatigue trial. Results Weak (r(s) = 0.27) and moderate (r(s) = 0.49) correlations were found between traditional peak torque and power output H:Q(fatigued), and traditional peak torque and power output H:Q(non-fatigued), respectively. Conclusion The present data suggested that power H:Q differs from traditional H:Q, particularly during fatigue in professional soccer players, which warrants further investigation on the potential use of power output H:Q ratios for injury prediction.

Automated summary

The study found different levels of correlation between traditional peak torque and power output H:Q values in professional soccer players, particularly during fatigue.