The response of endurance-adapted adults to intense anaerobic training.

The effects of a 6 week program of intense, intermittent hill running was investigated in 5 endurance-trained men (34-37) years. Venous lactate responses averaged 10.7 mM X 1(-1) during training. Biopsies were obtained from the vastus lateralis before and after training for determinations of histochemical classification, phosphagen concentrations (ATP and CP) and activities of total LDH and selected LDH isozymes. Indices of aerobic and anaerobic capacity were also measured. Significant improvements (P less than 0.01) were noted in training distance and loads employed in leg presses, also part of the training: the treadmill test for anaerobic capacity improved by 16.7% and the terminal blood lactate level increased 14%(P less than 0.05). No changes occurred in VO2 max, body fat per cent or anaerobic power. Muscle ATP concentration increased by 14.8% (P less than 0.01) whereas the tissue level of CP remained unchanged. Total LDH activity and the LDH isozymes (LDH-1, LDH-5 and LDH-2, 3, 4) were not altered by training. No changes in fibre distribution were observed. That adaptations to the anaerobic training did occur is evident, but the cellular locus remains to be elucidated further.