Fig. 6.

Unloaded shortening velocity (V_o) of fast MHC IIa fibers measured below and above 10% shortening in maximal (pCa 4.5) and half-maximal Ca²⁺ (pCa₅₀). A: representative plot of individual fibers from a young and old woman for V_o below (filled symbols) and above (open symbols) 10% shortening in both pCa 4.5 and pCa₅₀. B: group means for V_o below 10% shortening in both pCa 4.5 and pCa₅₀. C: group means for V_o above 10% shortening in both pCa 4.5 and pCa₅₀. There were no age or sex differences in V_o below or above 10% shortening in either pCa 4.5 or pCa₅₀. The horizontal line in each box plot indicates the median, while the whiskers represent 1.5 times the upper- and lower-interquartile range. Each dot is an individual fiber, with the number of fibers (n) displayed below the box plots. Data were analyzed using a nested ANOVA.