Near-infrared spectroscopy-derived muscle kinetics after moderate running exercise in healthy males: reliability and associations with parameters of aerobic fitness.

Abstract

What is the central question of this study? What is the reliability of near-infrared spectroscopy-derived muscle oxygen uptake ( ) kinetics following running exercise and what is the relationship between the time constant of off-kinetics and parameters of aerobic fitness? What is the main finding and its importance? The time constant of kinetics in gastrocnemius following moderate running exercise presents good to excellent reliability. In addition, it was well correlated with parameters of aerobic fitness, such as maximal speed of an incremental test, ventilatory threshold and pulmonary on-kinetics. Therefore, near-infrared spectroscopy-derived muscle oxidative capacity together with other physiological measurements may allow a concomitant local and systemic analysis of the components of the oxidative system. Near-infrared spectroscopy-derived muscle oxygen uptake ( ) kinetics following single-joint exercise has been used to assess muscle oxidative capacity. However, little evidence is available on the use of this technique following whole-body exercise. Therefore, this study aimed to assess the reliability of the NIRS-derived kinetics following running exercise and to investigate the relationship between the time constant of off-kinetics ( ) and parameters of aerobic fitness. After an incremental test to determine , first (VT1 ) and second (VT2 ) ventilatory thresholds, and maximal speed (Smax ), 13 males (age=21±4years; =55.9±3.4mlkg-1 min-1 ) performed three sets (two on the first day and one on a subsequent day) of two repetitions of 6-min running exercise at 90%VT1 . The pulmonary ( ) on-kinetics and off-kinetics in gastrocnemius were assessed. presented no systematic change and satisfactory reliability (the standard error of the measurement (SEM) and intraclass correlation coefficient of 4.21s and 0.49 for between transitions; and 2.65s and 0.74 averaging within each time set), with no difference (P>0.3) between the within- (SEM=2.92s) and between-day variability (SEM=2.78s and 2.19s between first vs. third set, and second vs. third set, respectively). (28.5±4.17s) correlated significantly (P<0.05) with Smax (r=-0.66), VT1 (r=-0.64) and time constant of the p on-kinetics (r=0.69). These findings indicate that NIRS-derived kinetics in the gastrocnemius following moderate running exercise is a useful and reliable parameter to assess muscle oxidative capacity.