Vastus lateralis oxygenation dynamics during maximal fatiguing concentric and eccentric isokinetic muscle actions

The present study aimed to assess whether high intensity exhaustive eccentric (ECC) exercise was associated with a greater decrease in muscle oxygenation compared to high intensity exhaustive concentric (CON) exercise during maximal isokinetic knee extensions. On two separate days, ten recreationally active participants performed maximal isokinetic concentric (KECON) and eccentric (KEECC) knee extension exercises at 60° s−1 until exhaustion. Muscle oxygenation profile and activity were acquired continuously from the vastus lateralis (VL) muscle using near-infrared spectroscopy, along with surface electromyography (sEMG). The torque output was significantly greater during KEECC (P < 0.01). Total time to exhaustion was longer in ECC condition (P < 0.01). The decrease in tissue oxygenation index observed between the beginning and end-exercise values was significantly greater during KEECC than during KECON (P < 0.05) while total haemoglobin volume did not differ significantly. KEECC resulted in a significant increase in end-exercise integrated sEMG (P < 0.05). We propose that the associated higher intramuscular pressure may have compressed blood vessels and led to a greater decrease in tissue oxygenation index. The observed end-exercise increase in neural drive during KEECC may have occurred to prevent from muscle performance decrease. These results suggest that, over time, repeated maximal ECC actions induce a greater O2 extraction compared to maximal CON actions.