Role of decreased carbohydrate oxidation on slower rises in ventilation with increasing exercise intensity after...

In these studies, we examined whether the rightward shift in steady-state minute ventilation (VE) versus O2 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 VE 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 VE with increasing exercise intensities were associated with a reduced reliance on CHOOX, (P < 0.01). Both before and after training, VE values in litres per minute rose as a linear VE = 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 VE 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.