Peak Oxygen Uptake During Running and Arm Cranking Normalized to Total and Regional Skeletal Muscle Mass Measured by Magnetic Resonance Imaging

The purposes of our study were to determine the peak oxygen uptake (V(.) >O(2peak)) per total or regional skeletal muscle (SM) mass using magnetic resonance imaging (MRI) and to investigate the relationships between SM mass and V(.) >O(2peak) during running and arm cranking. Eight male college swimmers aged 18-22 years [mean (SD) age 20.0 (1.3) years] were recruited to participate in this study. V(.) >O(2) during running and arm cranking were measured using an automated breath-by-breath mass spectrometry system. Contiguous MRI slices were obtained from the first vertebra cervicale to the malleolus lateralis (1.0-cm slice thickness, 0-cm inter-slice gap), resulting in a total of approximately 156 images for each subject. The absolute V(.) O(2peak) and the V(.) O(2peak) per body mass during running and arm cranking were 3.6 (0.6) l.min(-1), 54.4 (5.9) ml.min(-1).kg(-1) and 2.5 (0.5) l.min(-1), 36.9 (5.3) ml.min(-1).kg(-1), respectively. The absolute V(.) O(2peak) was higher ( P <0.05) during running than during arm cranking, but not the V(.) O(2peak) per regional area SM mass. The lower body SM mass was correlated to the V(.) O(2peak) during running ( r =0.95, P <0.001). All measurements and calculated values were expressed as the mean (SD) for the eight subjects. To eliminate the influence of body mass and fat-free mass (FFM), a regression analysis was performed on the mass-residuals of the V(.) O(2peak) during running and the lower body SM mass. The residuals of lower body SM mass were correlated to the residuals of V(.) O(2peak) during running, with respect to body mass ( r =0.90, P <0.001) and FFM ( r =0.82, P <0.05). These results suggest that the MRI-measured lower body SM mass was closely associated to the absolute V(.) O(2peak) during running, independently of body mass or FFM, and that the V(.) O(2peak) per regional SM mass corresponded, regardless of the type of exercise (upper or lower body).