Effect of different incremental exercise protocols on the determination of lactate and ventilatory thresholds.

The aerobic threshold (AeT) determined from ventilatory curves occurs at the same oxygen uptake and is independent of the rate of increase of power output in an incremental exercise test. On the other hand, it has been proposed that the AeT determined from blood lactate curves and the anaerobic threshold (AnT) determined from ventilatory curves may vary depending on the exercise protocol. Seven healthy subjects performed two incremental exercise tests to evaluate the effect of the rate of power increment on the AeT and the AnT determined from the break points in both ventilatory and venous blood lactate curves. The protocols on the cycle ergometer consisted of increments of 15 W every min (slow) or every 0.25 min (fast). When the results were expressed as the corresponding oxygen uptake, neither the lactate AeT (slow = 2.662 +/- 0.395 1/min; fast = 2.577 +/- 0.392 1/min; P greater than 0.05) nor the ventilatory AeT (slow = 2.737 +/- 0.426 1/min; fast = 2.583 +/- 0.555 1/min; P greater than 0.05) was significantly affected by the protocols. The lactate AnT (slow = 3.675 +/- 0.610 1/min; fast = 3.683 +/- 0.610 1/min; P greater than 0.05) and the ventilatory AnT (slow = 3.635 +/- 0.665 1/min; fast = 3.823 +/- 0.645 1/min; P greater than 0.05) were also not significantly affected by the protocols. The oxygen uptake corresponding to a blood lactate concentration of 2 mM was significantly higher for the fast protocol (slow = 3.235 +/- 0.735 1/min; fast = 4.005 +/- 0.643 1/min; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)