INVESTIGATING THE HAMSTRING-TO-QUADRICEPS MUSCLE STRENGTH RATIO IN A FATIGUED STATE

Abstract

Background: Muscle fatigue is known to reduce force production and alter neuromuscular performance; however, its effects on muscle balance, particularly the hamstring-to-quadriceps (H:Q) ratio, remain unclear. Understanding how fatigue influences both strength and muscle balance is important for injury prevention and performance assessment.Methods: Fifteen healthy, untrained adults (11 males, 4 females) participated in this study. Peak torque of the hamstrings and quadriceps was assessed using isokinetic dynamometry at two angular velocities (60°/s and 180°/s) before and immediately after a fatigue protocol consisting of repeated shuttle runs. The H:Q ratio was calculated at each velocity. Perceived exertion (RPE) and performance (distance covered across six laps) were also recorded. A repeated-measures ANOVA was conducted to examine the effects of time (pre vs. post) and velocity on muscle performance outcomes. Results: Fatigue resulted in significant reductions in peak torque, particularly at the higher velocity (180°/s), indicating greater fatigue-related decline under faster contraction conditions. In contrast, no significant changes were observed in the H:Q ratio following fatigue, suggesting that both muscle groups were affected proportionally. A significant main effect of velocity was found for the H:Q ratio, indicating differences between testing speeds independent of fatigue. Perceived exertion increased progressively across laps, confirming the effectiveness of the fatigue protocol, while performance showed a non-significant decline with substantial individual variability. Conclusion: These findings indicate that fatigue significantly impairs muscle force production but does not necessarily alter muscle balance as measured by the H:Q ratio. The results highlight the importance of considering contraction velocity when assessing fatigue effects and suggest that the H:Q ratio alone may not be sensitive to fatigue-related changes. Additionally, substantial individual variability in fatigue responses emphasizes the need for individualized assessment in both research and applied settings.