Context: Epidemiologic findings of higher incidences of hamstrings muscle strains during the latter stages of soccer match play have been attributed to fatigue.
Objective: To investigate the influence of soccer-specific fatigue on the peak eccentric torque of the knee flexor muscles.
Design: Descriptive laboratory study.
Setting: Controlled laboratory environment.
Patients or other participants: Ten male professional soccer players (age = 24.7 +/- 4.4 years, mass = 77.1 +/- 8.3 kg, Vo(2max) = 63.0 +/- 4.8 mL x kg(-1) x min(-1)).
Intervention(s): Participants completed an intermittent treadmill protocol replicating the activity profile of soccer match play, with a passive halftime interval. Before exercise and at 15-minute intervals, each player completed isokinetic dynamometer trials.
Main outcome measure(s): Peak eccentric knee flexor torque was quantified at isokinetic speeds of 180 degrees x s(-1), 300 degrees x s(-1), and 60 degrees x s(-1), with 5 repetitions at each speed.
Results: Peak eccentric knee flexor torque at the end of the game (T(300eccH105) = 127 +/- 25 Nm) and at the end of the passive halftime interval (T(300eccH60) = 133 +/- 32 Nm) was reduced relative to T(300eccH00) (167 +/- 35 Nm, P < .01) and T(300eccH15) (161 +/- 35 Nm, P = .02).
Conclusions: Eccentric hamstrings strength decreased as a function of time and after the halftime interval. This finding indicates a greater risk of injuries at these specific times, especially for explosive movements, in accordance with epidemiologic observations. Incorporating eccentric knee flexor exercises into resistance training sessions that follow soccer-specific conditioning is warranted to try to reduce the incidence or recurrence of hamstrings strains.
Keywords: athletic injuries; isokinetic activity.