The effects of high intensity training upon respiratory gas exchanges during fixed term maximal incremental exercise in man.

The response of respiratory gas exchanges to a 6 week high intensity training program was examined in 5 healthy males during fixed term maximal incremental treadmill exercise. Training was performed 3 d.wk-1 and consisted of a progressive series of repeated 15 sec and 30 sec maximal runs, and weight training exercises for the leg extensor muscles. Respiratory gases during the tests were continuously monitored using an on-line system. Muscle biopsy samples were obtained from the m. vastus lateralis before and after training for histochemical determination of fibre distribution based on myosin ATP-ase activity, and fibre cross-sectional area based on NADH-Tetrazolium Reductase activity. Training significantly increased the proportion of type IIa fibres (+5.9 +/- 2.0%, p less than 0.001) and decreased type I fibres (-6.3 +/- 2.0%, p less than 0.001), the distribution of type IIb fibres remained unchanged (+0.4 +/- 0.9%). Muscle cross-sectional area also showed a significant increase after training in type I (+318 +/- 215 microns 2, p less than 0.05), IIa (+652 +/- 207 microns 2, p less than 0.001) and IIb (+773 +/- 196 microns 2, p less than 0.001) fibres. During fixed term maximal incremental exercise the mean carbon dioxide output (VCO2) and mean respiratory exchange ratio (R = VCO2/VO2) were significantly increased (p less than 0.01) after training. The R-time relationship was at all times shifted to the left after training, being significantly (p less than 0.01) so over the final five min of exercise. No changes in mean exercise oxygen uptake (VO2), maximum oxygen uptake (VO2max) and maximum heart rate (FHRmax) were observed between tests.(ABSTRACT TRUNCATED AT 250 WORDS)