ROLE OF DECREASED CARBOHYDRATE OXIDATION ON SLOWER RISES IN VENTILATION WITH INCREASING EXERCISE INTENSITY AFTER TRAINING

In these studies, we examined whether the rightward shift in steady-state minute ventilation (V-E) versus O-2 uptake curves after training is more closely linked to the reduced CO2 production from carbohydrate oxidation (CHOOX) after training than to the attenuated increase in blood lactate concentration. Steady state V-E values and gas exchange were measured in eight previously sedentary men who underwent exercise tests of 60 W + 40 W every 6 min before and after a 9 week training programme of cycling approximately 40 min a day. Following training, the slower rises in V-E with increasing exercise intensities were associated with a reduced reliance on CHOOX, (P < 0.01). Both before and after training, V-E values in litres per minute rose as a linear V-E = 18 . CHOOX + 14, function of rates of CHOOX in grams per minute (r = 0.99), irrespective of a marked shift to the right in arterialized venous blood lactate concentration versus CHOOX curves following training (P < 0.01). Thus, slower increases in steady-state V-E values with increasing exercise intensities following endurance training appeared to be more closely linked to the decreased reliance on CHOOX than to the attenuated increase in blood lactate concentration.