Improved Exercise-Related Skeletal Muscle Oxygen Consumption Following Uptake of Endurance Training Measured Using Near-Infrared Spectroscopy

Siana Jones, Andrew D'Silva, Anish Bhuva, Guy Lloyd, Charlotte Manisty, James C. Moon, Sanjay Sharma, Alun D. Hughes

Skeletal muscle metabolic function is known to respond positively to exercise interventions. Developing non-invasive techniques that quantify metabolic adaptations and identifying interventions that impart successful response are ongoing challenges for research. Healthy non-athletic adults (18-35 years old) were enrolled in a study investigating physiological adaptations to a minimum of 16 weeks endurance training prior to undertaking their first marathon. Before beginning training, participants underwent measurements of skeletal muscle oxygen consumption using near-infrared spectroscopy (NIRS) at rest (resting muscle[Formula: see text]O2) and immediately following a maximal exercise test (post-exercise muscle[Formula: see text]O2). Exercise-related increase in muscle[Formula: see text]O2 (Δm[Formula: see text]O2) was derived from these measurements and cardio-pulmonary peak[Formula: see text]O2 measured by analysis of expired gases. All measurements were repeated within 3 weeks of participants completing following the marathon and marathon completion time recorded. Muscle[Formula: see text]O2 was positively correlated with cardio-pulmonary peak[Formula: see text]O2 (r = 0.63, p < 0.001). Muscle[Formula: see text]O2 increased at follow-up (48% increase; p = 0.004) despite no change in cardio-pulmonary peak[Formula: see text]O2 (0% change; p = 0.97). Faster marathon completion time correlated with higher cardio-pulmonary peak[Formula: see text]O2 (rpartial = -0.58, p = 0.002) but not muscle[Formula: see text]O2 (rpartial = 0.16, p = 0.44) after adjustment for age and sex [and adipose tissue thickness (ATT) for muscle[Formula: see text]O2 measurements]. Skeletal muscle metabolic adaptions occur following training and completion of a first-time marathon; these can be identified non-invasively using NIRS. Although the cardio-pulmonary system is limiting for running performance, skeletal muscle changes can be detected despite minimal improvement in cardio-pulmonary function.