Fig. 2. Oxygen consumption (_O2) (A), lactate production (B), total ATP production (C), twitch force (D) and twitch force relative to total ATP production (E) are presented for isolated turtle (left) and trout (right) ventricular muscle. Preparations were either stimulated at 30 min^-1 (N=8 for both turtle and trout) or left to rest (N=7 for both turtle and trout). For all parameters, values are means ± S.E.M. of the average obtained over the 30 min period of oxygenation and over the last 30 min of the 70 min hypoxic period, respectively. Asterisks signify differences between stimulation and rest, signifies differences between oxygenation and hypoxia and signifies differences between turtle and trout.