Muscle Oxygenation Threshold in More and Less Active Muscles and 3,000-m Running Pace

This study determined and compared the second muscle oxygenation threshold (MOT2) in the vastus lateralis (VL) (more active) and biceps brachii (BB) (less active) muscles in the graded exercise test (GXT). Furthermore, we investigated the correlation between BB and VL MOT2 with the 3,000-m time trial, as well as the muscle oxygenation responses during the free-paced strategy of elite endurance athletes. Nine elite men's middle- and long-distance runners from the Brazilian Paralympic Endurance Team performed the GXT in a laboratory setting. MOT2 was determined by the breakpoint in the tissue saturation index (TSI) curve in both muscles by wearable near-infrared spectroscopy (NIRS). After 48 h, athletes performed a 3,000-m running test on an outdoor athletics track while monitoring the oxygenation in both muscles. MOT2 velocity values in BB (19.3±1.3 km.h^-1) and VL (19.4±1.2 km.h^-1) did not show a significant difference between them (p>0.05). We observed a significant correlation between BB and VL MOT2 with 3,000-m mean velocity (r=0.88 and 0.86, respectively, p<0.05). Our results reinforce that the maximal aerobic capacity determined in different muscles influenced the athletes' performance in the 3,000-m running. The muscle oxygenation responses showed that BB and VL worked in an integrated manner during the GTX and in the 3,000-m running effort.