Introduction Functional hamstring-to-quadriceps ratio (H/Q: ratio between eccentric hamstring to concentric quadriceps torque) is gaining popularity in soccer as potential predictor of injury risk. It has been shown that after fatiguing exercise tasks, H/Q is reduced, and this may increase the injury risk(Rahnama,2003). The aim of this study was to examine the effect of fatigue on H/Q ratio after a soccer match simulation and to examine whether it is influenced by sport-specific experience (i.e. sport-specific adaptations). Methods For this cross-sectional study, 22 amateur soccer players and 18 control (sport science students practicing different sports like swimming, running, etc.) completed the Loughborough Intermittent Shuttle Test (LIST). During fatiguing exercise, RPE and heart rate was monitored. Pre and post LIST, participants performed 1) isokinetic strength test at 60°/s, 180°/s and 300°/s on dominant (D) and non dominant (ND) limb, 2) Squat Jump (SJ) and Counter Movement Jump (CMJ). Dependent variables were analysed using a mixed 3-way ANOVA. Results No three-way interaction we found. After LIST, D showed a significant reduction in H/Q at 180°/s (CI 95% -0.150 to -0.055) and 300°/s (-0.149 to -0.044), and there was a trend at 60°/s (-0.065 to 0.002, p=0.065). In ND limb, significant reduction in H/Q occurred only at 60°/s (-0.080 to -0.011). Eccentric peak torque flexion angle resulted significantly increased in D at 60°/s (7.3° to 14.2°), 180°/s (3.6° to 13.5°) and 300°/s (1.8° to 9.4°) and in ND at 60°/s (5.3° to 12.1°), 180°/s (8.5° to 19.1°) and 300°/s (2.4° to 9.8°). In both limbs concentric peak torque angle during extension did not change. Two way interaction was found for RPE (p<0,01) and heart rate were significantly lower in soccer players. Both SJ and CMJ showed decrement in all subjects, but it was significantly greater in control. Discussion Functional H/Q ratio was significantly altered by exercise-induced fatigue, especially in dominant limb, confirming A previous study(Delextrat,2010). A novel finding was that the peak angle during eccentric knee flexion was left shifted indicating an alteration of torque-length relationship. This latter result may be an additional factor influencing the injury risk that warrants further studies. However, it is not different between groups, suggesting that this mechanism Is not influenced by sport background. Delextrat, A et al. (2010). The use of the functional H:Q ratio to assess fatigue in soccer. Int. J of sports med., 31(3), 192–7. Rahnama, N. et al. (2003). Muscle fatigue induced by exercise simulating the work rate of competitive soccer. J sports sci., 21(11), 933–42.
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