Fig. 8. Effects of varying contraction frequency on mean work output per cycle (A), enthalpy output per cycle (B) and net mechanical efficiency, _Net (C) (N=6). The duration of the initial stretch or isometric period was 75 ms or 15 % of the cycle duration, and shortening was 10 % L_max, where L_max is the length at which active force production is maximal. Letters indicate statistically significant differences. Values are means ± S.E.M.