Figure 2. Time to task failure and associations with initial power and peak rates of relaxation of muscle.

A. Time to task failure of young and old men for the dynamic and isometric postural contractions. Shown are the means (± SEM). * denotes an age difference for the isometric task (P < 0.05). B. The difference in the time to failure (between the isometric and the dynamic contraction for those subjects who performed both protocols, n = 6 young and 14 old men) was associated with the peak power during initial maximal velocity concentric contractions performed prior to the fatiguing contractions (r = −0.54, r² = 0.29, P = 0.015). C–D. Time to task failure was associated with the peak rate of relaxation for the isometric postural contraction (C, r = -0.43, r² = 0.19, n = 7 young and 14 old men) and dynamic contraction (D, r = -0.44, r² = 0.20, n = 9 young and 16 old men). A faster rate of relaxation was associated with a briefer time to failure for both tasks (P < 0.05). Note that the y-axis for panels C and D is inverted. Larger negative numbers indicate more rapid relaxation.