Effects of exercise intensity on post-exercise oxygen consumption of the vastus lateralis

Post-exercise muscle oxygen consumption rate (mVO 2 ) may contribute to understanding responses to and recovery from exercise. Purpose: To measure post-exercise mVO 2 of the vastus lateralis (VL) muscle after various exercise intensities using near-infrared spectroscopy (NIRS). Methods: Twenty healthy individuals, 18-35 years old, participated in two testing sessions. A NIRS device was placed on the belly of the VL to measure differences in oxygenated and deoxygenated hemoglobin (Hb diff ). Electrodes were placed proximally and distally to the NIRS device, and a cuff capable of rapid inflation was placed on the upper leg. mVO 2 at rest was assessed as the slope of the Hb diff signal (% s -1 ) during 3 x 30 second cuff inflations at 300 mmHg. Neuromuscular electrical stimulation (NMES) was applied for 30 seconds, and mVO 2 was assessed 5 minutes later. Participants performed maximal and submaximal (60% VO 2 peak) cycling tests 1 week apart, and mVO 2 was assessed 15 min later. Desaturation slopes (% s -1 ) were calculated in Hb diff signals to measure mVO 2 . Results: On average, mVO 2 5 minutes post-NMES was 1.8-fold higher compared to resting ( p < 0.001). mVO 2 was 4.2-fold and 2.7-fold higher 15 minutes after maximal and submaximal cycling, respectively, compared with resting (both p < 0.001). Blood lactate was elevated 10 minutes after maximal (10 ± 3 mmol/L) and submaximal (4 ± 3 mmol/L) cycling (both p < 0.001). Conclusions: Muscle metabolism remained highly elevated 15 minutes after cycling exercise. NIRS-based mVO 2 may have value as an indicator of post-exercise muscle metabolism.