Independence of ventilation and blood lactate responses during graded exercise

The effect of power output increment, based on an increase in pedal rate, on blood lactate accumulation during graded exercise is unknown. Therefore, in the present study, we examined the effect of two different rates of power output increments employing two pedal rates on pulmonary ventilation and blood lactate responses during graded cycle ergometry in young men. Males (n=8) with an mean (SD) peak oxygen uptake of 4.2 (0.1) 1·min^–1 served as subjects. Each subject performed two graded cycle ergometer tests. The first test, conducted at 60 rev· min^–1, employed 4 min of unloaded pedaling followed by a standard power output step increment (SI) of 60 W every 3rd min. The second test, conducted at 90 rev·min^–1, employed 4 min of unloaded pedaling followed by a high power output step increment (HI) of 90 W every 3rd min. Venous blood was sampled from a forearm vein after 5 min of seated rest, 4 min of unloaded pedaling, and every 3rd min of graded exercise. Peak exercise values for heart rate, oxygen uptake (O₂), and ventilation (_E) were similar (P > 0.05) for SI and HI exercise, as was the relationship between_E andO₂, and between_E and carbon dioxide production (CO₂). However, the relationship between blood lactate concentration andO₂ was dissimilar between SI and HI exercise with blood lactate accumulation beyond the lowest ventilatory equivalent of oxygen, and peak exercise blood lactate concentration values significantly higher (P < 0.05) for SI [12.8 (2.6) mmol·l^–1] compared to HI [8.0(1.9) mmol·l^–1] exercise. Our findings demonstrate that blood lactate accumulation and_E during graded exercise are dissociated. Blood lactate accumulation is influenced by the rate of external power output increment, while_E is related toO₂ andCO₂.