The goal of this study was to describe the isokinetic thigh muscle strength profile of professional male football players in Australia. Concentric (60° and 240°/second) and eccentric (30° and 120°/second) hamstrings and quadriceps isokinetic strength was assessed with a HUMAC NORM dynamometer. The primary variables were bilateral concentric and eccentric hamstring and quadriceps peak torque ratios, concentric hamstring-quadriceps peak torque ratios, and mixed ratios (eccentric hamstring 30°/second ÷ concentric quadriceps 240°/second). Hamstring strength imbalance was defined as deficits in any two of: bilateral concentric hamstring peak torque ratio < 0.86, bilateral eccentric hamstring peak torque ratio < 0.86, concentric hamstring-quadriceps ratio < 0.47, mixed ratio < 0.80. Fifty-five strength tests involving 42 players were conducted. Ten players (24%) were identified as having hamstring strength imbalance. Athletes with strength imbalance had significantly lower concentric and eccentric bilateral hamstring peak torque ratios at all angular velocities tested; and decreased eccentric quadriceps peak torque (30°/second) in their stance leg, in comparison to those without strength imbalance. Approximately one in four players had preseason hamstring strength imbalance; and all strength deficits were observed in the stance leg.
Concentric and eccentric hamstrings strength imbalance could affect in-season football performance, and might have implications for the future risk of injury.