Association Between Whole-body And Skeletal Muscle Oxygen Consumption Rate At Rest And While Ambulatory

Near-infrared spectroscopy (NIRS) allows for non-invasive measurement of oxy- and deoxy-hemoglobin content in skeletal muscle (SM) and can be used to measure SM oxygen consumption rate. However, scarce studies have evaluated the relationship between SM and whole-body O2 consumption rates. PURPOSE: The purpose of our study was to investigate the relationship between NIRS-derived SM O2 consumption rate (mVO2) and whole-body O2 consumption (wbVO2) at rest and while walking. METHODS: mVO2 was measured by placing a NIRS device on the belly of the medial gastrocnemius (MG) of the participant’s dominant leg (N = 26, 25 ± 8 years old). A pneumatic rapid inflation cuff was placed proximal to the testing site for occlusion of arterial blood flow. After a 5-minute rest while lying supine, average resting mVO2 was measured during three rounds of 30s arterial occlusion and 30s of rest. Ambulatory mVO2 was measured during a 10s arterial occlusion immediately following 6 minutes (group 1, N = 12) or 5 minutes (group 2, N = 14) of walking at usual gait speed over a 40 m course. In group 1, whole-body oxygen consumption (wbVO2) rate was measured during 15 minutes of rest by indirect calorimetry and during ambulation by portable indirect calorimetry. In group 2, wbVO2 rate was measured during rest (10 minutes) and ambulation by portable indirect calorimetry. The association between wbVO2 rate and mVO2 rate was modeled through linear regression analysis, adjusted for group and muscle tissue thickness. RESULTS: At rest, a significant positive association (β = 11.1, P < 0.001) was observed between mVO2 (mean: 0.27 ± 0.07%/s) and wbVO2 (mean:3.7 ± 0.8 mL/kg/min). Similarly, a significant positive association (β = 1.1, P < 0.05) was observed between walking mVO2 (mean: 6.7 ± 2.5%/s) and walking wbVO2 (mean: 13.9 ± 3.2 mL/kg/min). CONCLUSION: An association between whole-body and muscle oxygen consumption rate was detected both at rest and during ambulation. These findings suggest the use of NIRS to accurately assess SM metabolism and potential changes to SM metabolism that may occur as a result of disease, muscle damage, or training/rehabilitation. Supported by: Supported by Towson University College of Health Professions Summer Undergraduate Research Institute.