Cross-adaptive responses to different forms of leg training: skeletal muscle biochemistry and histochemistry.

The influence of a program of high intensity training and of a combined program of high intensity training and prolonged submaximal training on adaptations to the vastus lateralis muscle was investigated in two groups of elite athletes. The high intensity training (H) consisted of ice hockey practices and games over a 14-week period while the combined program (HI-LO) included the addition of supplementary sessions of cycling, three times per week, progressively increasing from 30 to 45 min per session and at an intensity of 70% VO2max. Determinations of enzyme activities representative of energy supplying pathways revealed no change in 3-hydroxyacl CoA dehydrogenase (HADH), total phosphorylase (PHOSP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), and a 7% increase (p less than 0.05) in succinate dehydrogenase (SDH). The addition of the supplementary program caused no further adaptation in the metabolic profile. Similarly, neither the HI nor the HI-LO program induced any alteration in the percentage fibre type (slow twitch (ST) vs. fast twitch (FT) or the subtypes (FTa, FTb, FTc). Reductions in the size (p less than 0.05) of ST fibres were noted for both the HI and the HI-LO training programs. In contrast, increases in capillarization (p less than 0.05) were found for both the ST (23%) and FTa (32%) fibres for the HI-LO program whereas a reduction in capillarization (21%) occurred in the FTa fibres as a result of HI training only. It is concluded that metabolic differentiation does not appear to occur in a manner consistent with the conditions of energy expenditure at least for high intensity work.