Fig. 3. Recovery of cardiac function following 30 min of severe hypoxia, measured as the percentage recovery of maximum force by ventricular strips [Gesser, 1977; open circles, rainbow trout (N=5) and closed circles, carp (N=5)], or as the % recovery of _MAX in in situ trout hearts (Faust et al., 1994; open square, N=8). Workload during the hypoxic period was similar between studies. The ventricular strips used by Gesser (1977) were developing maximum force, but at a contraction rate (0.2 Hz, 12 contractions min^–1) much lower than measured in vivo (50–60 beats min^–1). By contrast, the power output of the hearts used in Faust et al. (2004) was approx. 1/6th of maximum. Reprinted with permission from the Journal of Experimental Biology.