Pi→ATP flux compared with other measures of oxidative ATP synthesis in some published studies of resting human muscle. The
circles represent individual subjects’ data points from Schmid et al. (2), showing the Pi→ATP flux measured by 31P MRS MT plotted against oxidative ATP synthesis rate in normally perfused muscle estimated as the rate of nonoxidative ATP
synthesis by 31P MRS during temporary ischemia; also shown is the linear regression line through the individual data points [compared with
Fig. 4e in Schmid et al. (2)] extended to the x-axis. The diamonds represent mean ± SEM data from Ref. 16, showing the Pi→ATP flux measured by 31P MRS MT plotted against oxidative ATP synthesis estimated from TCAC rates measured by 13C MRS; results are shown for young subjects (closed symbols) and elderly, relatively IR, subjects (open symbols), linked by
a dotted line. The dashed line is the line of identity.