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

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

JOURNAL=Frontiers in Physiology

VOLUME=Volume 8 - 2017

YEAR=2017

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2017.01018

DOI=10.3389/fphys.2017.01018

ISSN=1664-042X

ABSTRACT=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 muscleV̇O2) and immediately following a maximal exercise test (post-exercise muscleV̇O2). Exercise-related increase in muscleV̇O2 (ΔmV̇O2) was derived from these measurements and cardio-pulmonary peakV̇O2 measured by analysis of expired gases. All measurements were repeated within 3 weeks of participants completing following the marathon  and marathon completion time recorded. 
MuscleV̇O2 was positively correlated with cardio-pulmonary peakV̇O2 (r=0.63, p<0.001). MuscleV̇O2 increased at follow-up (48% increase; p=0.004) despite no change in cardio-pulmonary peakV̇O2 (0% change; p=0.97). Faster marathon completion time correlated with higher cardio-pulmonary peakV̇O2 (rpartial=-0.58, p=0.002) but not muscleV̇O2 (rpartial=0.16, p= 0.44) after adjustment for age and sex (and adipose tissue thickness for muscleV̇O2 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.