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

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

doi:10.3389/fphys.2017.01018

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 muscleO2) and immediately following a maximal exercise test (post-exercise muscleO2). Exercise-related increase in muscleO2 (ΔmO2) was derived from these measurements and cardio-pulmonary peakO2 measured by analysis of expired gases. All measurements were repeated within 3 weeks of participants completing following the marathon and marathon completion time recorded. MuscleO2 was positively correlated with cardio-pulmonary peakO2 (r = 0.63, p < 0.001). MuscleO2 increased at follow-up (48% increase; p = 0.004) despite no change in cardio-pulmonary peakO2 (0% change; p = 0.97). Faster marathon completion time correlated with higher cardio-pulmonary peakO2 (rpartial = −0.58, p = 0.002) but not muscleO2 (rpartial = 0.16, p = 0.44) after adjustment for age and sex [and adipose tissue thickness (ATT) for muscleO2 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.

Highlights

Skeletal muscle metabolic adaptions with endurance exercise training are well-recognized (Gollnick et al, 1973; Holloszy and Booth, 1976)
We aimed to (1) describe non-invasive local measurements of muscleV O2 in the gastrocnemius at rest and immediately after peak exercise using near-infrared spectroscopy (NIRS). (2) compare muscleV O2 with cardiopulmonary peak V O2 assessed simultaneously by cardio-pulmonary exercise test (CPET), and (3) investigate the effect of ∼6 months of endurance training in healthy individuals preparing for a first marathon on muscleV O2 and cardio-pulmonary peak V O2, and how these related to firsttime marathon running performance
In these young, healthy individuals, a comparatively low-level of endurance training, while not sufficient to noticeably improve cardio-pulmonary function, still led to positive skeletal muscle adaptations resulting in improved oxygen extraction following exercise

Summary

Introduction

Skeletal muscle metabolic adaptions with endurance exercise training are well-recognized (Gollnick et al, 1973; Holloszy and Booth, 1976). It is generally accepted that in humans, whole body peak V O2, as measured by analysis of expired gases, is usually limited by the rate of oxygen delivery, and not by the rate of uptake/utilization in the muscle (Bassett and Howley, 2000). It remains unclear whether adaptation of one or other of these systems to a greater or lesser extent occurs. Increased physical activity, but not necessarily heavy exercise training, has been show to enhance metabolic health independently of cardio-respiratory fitness (Laye et al, 2015)

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