Fig. 1. Haematocrit and blood oxygen capacity of 12 surface-swimming (control) and 12 dive-conditioned muskrats prior to (pre-training) and following 9–11 weeks of training (post-training) in the laboratory (see text for details). Values are means + 1 S.E.M. For each variable, means sharing the same letter are not significantly different (P>0.05).