Effects of exercise intensity on postexercise oxygen consumption of the vastus lateralis

Abstract

Postexercise muscle oxygen consumption (mV O2) rate may contribute to understanding responses to and recovery from exercise. To measure postexercise mV O2 of the vastus lateralis (VL) muscle after various exercise intensities using near-infrared spectroscopy (NIRS). Twenty healthy individuals, 18–35 yr old, participated in two testing sessions. An NIRS device was placed on the belly of the VL to measure differences in oxygenated and deoxygenated hemoglobin (Hbdiff). Electrodes were placed proximally and distally to the NIRS device, and a cuff capable of rapid inflation was placed on the upper leg. mV O2 at rest was assessed as the slope of the Hbdiff signal (% s-1) during 3 × 30-s cuff inflations at 300 mmHg. Neuromuscular electrical stimulation (NMES) was applied for 30 s, and mV O2 was assessed 5 min later. Participants performed maximal and submaximal (60% V O2peak) cycling tests 1 wk apart, and mV O2 was assessed 15 min later. Desaturation slopes (% s-1) were calculated in Hbdiff signals to measure mV O2. On average, mV O2 5 min post-NMES was 1.8-fold higher compared with resting (P < 0.001). mV O2 was 4.2-fold and 2.7-fold higher 15 min after maximal and submaximal cycling, respectively, compared with resting (both P < 0.001). Blood lactate was elevated 10 min after maximal (10 ± 3 mmol/L) and submaximal (4 ± 3 mmol/L) cycling (both P < 0.001). Muscle metabolism remained highly elevated 15 min after cycling exercise. NIRS-based mV O2 may have value as an indicator of postexercise muscle metabolism.