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

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] O(2)) and immediately following a maximal exercise test (post-exercise muscle [Formula: see text] O(2)). Exercise-related increase in muscle [Formula: see text] O(2) (Δm [Formula: see text] O(2)) was derived from these measurements and cardio-pulmonary peak [Formula: see text] O(2) 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] O(2) was positively correlated with cardio-pulmonary peak [Formula: see text] O(2) (r = 0.63, p < 0.001). Muscle [Formula: see text] O(2) increased at follow-up (48% increase; p = 0.004) despite no change in cardio-pulmonary peak [Formula: see text] O(2) (0% change; p = 0.97). Faster marathon completion time correlated with higher cardio-pulmonary peak [Formula: see text] O(2) (r(partial) = −0.58, p = 0.002) but not muscle [Formula: see text] O(2) (r(partial) = 0.16, p = 0.44) after adjustment for age and sex [and adipose tissue thickness (ATT) for muscle [Formula: see text] O(2) 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.