Slower trabecula shortening kinetics during work-loop contractions. (A) Extent of shortening signifies the width of the work-loop (Fig. 6 C), and is expressed as a percentage of L_o. The average relations of extent of shortening and active stress (relative to peak stress at L_o) were fitted using quadratic regression. (B) Velocity of shortening was quantified as the slope of the length trace at the shortening phase of the work-loop (Fig. 6 A). The average relations of velocity of shortening and active stress (relative to peak stress at L_o) were fitted using cubic regression. (C) Power of shortening was quantified as the product of velocity of shortening and active stress. The average relations of power of shortening and active stress (relative to peak stress at L_o) were fitted using cubic regression with both variables fixed at zero at the origin. (D) MHC mRNA expression (measured by the 2^−ΔΔCt method) of the α and β isoforms. Data were expressed as fold change relative to the control group (n = 9 per group). In A–C, control rat (solid lines), hypertrophic rat (broken lines), n = 12 trabeculae. SEM is superimposed at peak values for each relation. The difference between regression lines was analyzed by the random coefficient model; *, P < 0.05. Insets in each panel show data from an exemplar trabecula. In D, graphs show mean ± standard error. Data analyzed by Student’s t test; *, P < 0.05.