Muscle Oxygenation during Prolonged Concentric and Eccentric Exercises in Well-trained Males

Understanding how training status influences muscle oxygen dynamics during resistance exercise is crucial for optimizing exercise prescriptions and performance adaptations. However, limited information is available regarding muscle oxygenation responses during fatigue resistance exercises across different training levels. Therefore, this study aimed to compare the effects of long-concentric (CON-L) and long-eccentric (ECC-L) resistance exercise on muscle oxygen dynamics in recreationally trained (RTR) and well-trained (WTR) individuals. Eleven male RTR and nine male WTR participants performed unilateral leg extension exercises, with each leg randomly assigned to CON-L (5 s concentric, 1 s isometric, and 1 s eccentric) or ECC-L (1 s concentric, 1 s isometric, and 5 s eccentric). Each protocol was performed to volitional failure for three sets with a 2-min rest between sets. Muscle oxygen saturation (StO 2 ) of the vastus lateralis was continuously monitored via near-infrared spectroscopy. Time-normalized StO 2 values were analyzed at 20% intervals, and the minimum StO 2 during each set was recorded. Results indicated that WTR individuals exhibited significantly lower StO 2 during exercise compared to RTR, suggesting greater muscle oxygen utilization. No significant differences were observed between CON-L and ECC-L in either group. These findings suggest that training status plays a key role in muscle oxygen dynamics during resistance exercise.