Effects of muscle fatigue on quadriceps muscle performance in healthy amateur soccer players

Quadriceps femoris muscle (QFM) fatigue has a detrimental impact on athlete performance. Therefore, it is crucial to evaluate various performance parameters under fatigued conditions. This study aimed to assess the performance of the QFM during both concentric and eccentric contractions before and after fatigue in the lower extremities of healthy amateur soccer players. Twenty-four healthy amateur soccer players performed three consecutive knee extension and flexion movements concentrically and eccentrically at a velocity of 120°/s with maximum effort, using a Biodex dynamometer. Fatigue was induced by a protocol involving repetitive concentric knee extension and flexion movements at 120°/s, with a load of 50% of maximal voluntary isometric contraction (MVIC) of the QFM until its moment declined to 50% of MVIC. Separate 2-way analyses of variance were conducted to assess the influence of contraction and fatigue on various isokinetic parameters. No significant interaction effect between contraction and fatigue was observed for any of the parameters. There was a significant main effect of fatigue on average power for both lower extremities. However, no significant main effect of fatigue was observed for normalized peak moment, angle of peak moment, moment at 0.2s, total work, acceleration, and deceleration times. In contrast, significant main effects of contraction were noted for normalized peak moment, moment at 0.2s, average power, acceleration, and deceleration times in both lower extremities. Average power appeared as the most sensitive performance parameter to fatigue. To enhance QFM performance, emphasizing eccentric exercises during training and conditioning programs could be beneficial for athletes. •Isokinetic contractions enable the extraction of multiple performance parameters for evaluating the QFM.•Evaluation across different muscle contractions enhances the understanding of QFM fatigue resistance and functional capacity.•Average power emerged as the most sensitive measure of QFM performance under fatigue, indicating a decline in performance.•Prioritizing intensive exercises to challenge the QFM's eccentric functional capacity may enhance performance.•Eccentric functional capacity appears to be a crucial factor influencing performance under fatiguing conditions.