Effects of eccentric exercise on optimum length of the knee flexors and extensors during the preseason in professional soccer players

Abstract Objective To assess the effects of eccentric exercise on optimum lengths of the knee flexors and extensors during the preseason in professional soccer. Design Twenty-eight athletes from a professional Spanish soccer team (Division II) were randomly assigned to an eccentric exercise intervention group (EG) or a control group (CG). Over the four-week period two athletes from the control group suffered RF injuries and two athletes were contracted by other clubs. After these exclusions, both groups (EG, n = 13; and CG, n = 11) performed regular soccer training during the four-week preseason period. Results After the four weeks, the optimum lengths of the knee flexors were significantly (P < 0.05) increased by 2.3° in the CG and by 4.0° in the EG. The change in the EG was significantly (P < 0.05) greater than that of the CG. The optimum lengths of the knee extensors were significantly increased only in the EG by 6.5°. Peak torque levels and ratios of quadriceps to hamstring (Q/H ratios) were not significantly altered throughout the study for either group. Conclusion Eccentric exercise can increase the optimum lengths of both the knee extensors and knee extensors flexors during the preseason in professional soccer.