Influence of prolonged intermittent high-intensity exercise on knee flexor strength in male and female soccer players

This study investigated the effect of an acute, prolonged, intermittent, high-intensity single-leg pedalling exercise task (PIHIET) on the isokinetic leg strength of the knee flexors in six male and seven female collegiate soccer players. Following determination of single-leg VO2peak, subjects completed a PIHIET designed to simulate the energetics of soccer match play (~90 min in total; ~70% single-leg VO2peak). Pre-, mid- and post-PIHIET gravity-corrected indices of knee flexion peak torque (PT) and range of motion-relativised torque at 15% of knee flexion (RRT15%; 0% = full knee extension) were assessed at a lever-arm angular velocity of 1.05 rads-1 for intervention and control limbs using an isokinetic dynamometer. Repeated measures ANOVAs revealed significant condition (PIHIET, control) time (pre-, mid-, post-PIHIET) interactions for knee flexion PT (F [2,22]=26.2; P<0.001) and RRT15% (F [2,22]=20.1; P<0.001). Flexion PT and RRT15% were observed to decrease, pre- to post-intervention, from 92.8 (28.7) Nm to 72.1 (28.0) Nm and from 63.8 (17.5) Nm to 47.9 (18.4) Nm respectively, for the intervention limb alone. These data corresponded to 22.3% and 24.9% mean reductions pre-post intervention in PT and RRT15%. Exploratory post hoc analysis of the pattern of the relative deterioration (%) of PT and RRT15%, for the intervention limb alone, revealed a three-way interaction [group (male, female) x parameter (PT, RRT15%) x assessment phase (pre- to mid-PIHIET, mid- to post-PIHIET)] (F 1,11=5.2; P<0.05). This interaction characterised a greater deterioration of strength performance during the mid- to post-PIHIET assessment phase, at the extremes of range of motion (RRT15%) for the female group. The greater percentage of mid-post phase strength loss observed in women near the end-range extension may potentially be implicated in the higher incidence of knee injury reported in female soccer players.sch_phyAbernethy P (1993) Influence of acute endurance activity on isokinetic leg strength. J Strength Cond Res 7:141-146 Craig BW, Lucas J, Pohlman R, Stelling H (1991) The effects of running, weightlifting and a combination of both on growth hormone release. J Appl Sports Sci Res 5:198-203 Fu FH (1993) Biomechanics of knee ligaments. J Bone Joint Surg Am 75: 1716-1727 Gleeson NP, Mercer TH (1992) Reproducibility of isokinetic leg strength and endurance characteristics of adult men and women. Eur J Appl Physiol 65:221-228 Gleeson NP, Mercer TH, Reilly T, Rakowski S, Rees D (1998) The influence of acute endurance activity on leg neuromuscular and musculoskeletal performance. Med Sci Sports Exerc 30: 596-608 Gleeson NP, Rees D, Walters M, Minshull C, Kyffin I, Mercer TH (2003) The effects of a three-week resistance conditioning programme on indices of neuromuscular and musculoskeletal performance of the knee joint in women. J Sports Sci 20: (in press) Hawkins RD, Fuller CW (1999) A prospective epidemiological study of injuries in four English professional football clubs. Br J Sports Med 33:196-203 Hewett TE, et al (1999) Am J Sports Med 27:699-705 Hutchinson MR, Ireland ML (1995) Knee injuries in female athletes. Sports Med 19:288-302 Lindenfield TN, et al (1994) Am J Sports Med 22: 364-371 Mercer TH, Gleeson NP, Claridge S, Clement S (1998) Prolonged intermittent high intensity exercise impairs neuromuscular performance of the knee flexors. Eur J Appl Physiol Occup Physiol 77:560-562 Noyes FR, Mooar PA, Matthews DS, Butler DL (1983) The symptomatic anterior-cruciate-deficient knee. Part I: the longterm functional disability in athletically active individuals. J Bone Joint Surg Am 65:154-162 Ryder SH, Johnson RJ, Beynnon BD, Ettlinger CF (1997) Prevention of ACL injuries. J Sport Rehabil 6:80-9689pub969pub