Fig. 4. Percentage changes in mitochondrial volume density Vv(mt,f) (A) and the length density of capillaries Jv(c,f) (B) after 6 weeks of endurance training in hypoxia (Hyp) or normoxia (Nor) at individual anaerobic threshold (high) or at a level of training approximately 25% below individual anaerobic threshold (low) (Vogt et al., 2001). Values are means + S.E.M. (N=8 for both normoxia groups; N=7 for both hypoxia groups). *Significant difference between pre- and post-training values (P<0.05).