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. Author manuscript; available in PMC: 2020 Aug 1.
Published in final edited form as: Curr Opin Physiol. 2019 May 10;10:118–127. doi: 10.1016/j.cophys.2019.05.004

Figure 4. Force-velocity and force-power curves of fast MHC II fibers from young and old men at 15°C.

Figure 4.

Absolute peak power (PPw) and peak isometric force (Po) of the fast MHC II fibers from young adults (A) were ~2-fold greater than in fibers from the old adults (B). The age differences in absolute PPw and Po were explained entirely by differences in the size of the fibers between young and old adults. The insets are digital images taken of young and old adult fast fibers at 800x magnification that are representative of the average size of the fast MHC II fibers studied in the young and old adults. The combined pH 6.2 and 30 mM Pi condition caused significant decreases in Vmax, Po and PPw compared to the condition mimicking quiescent human skeletal muscle (pH 7.0 + 4 mM Pi) in fibers from young and old adults; however, the relative reductions did not differ with age. The variances around the mean curves were omitted for clarity. The figure was modified with permission from [10].