THE VENTILATORY THRESHOLD GIVES MAXIMAL LACTATE STEADY-STATE

The purpose of this study was to examine whether the ventilatory threshold (Th(v)) would give the maximal lactate steady state ([la]ss, max), which was defined as the highest work rate (W) attained by a subject without a progressive increase in blood lactate concentration [la]b at constant intensity exercise. Firstly, 8 healthy men repeated ramp-work tests (20 W.min-1) on an electrically braked cycle ergometer on different days. During the tests, alveolar gas exchange was measured breath-by-breath, and the W at Th(v) (W(Thv)) was determined. The results of two-way ANOVA showed that the coefficient of variation of a single W(Thv) determination was 2.6%. Secondly, 13 men performed 30-min exercise at W(Thv) (Th(v) trial) and at 4.9% above W(Thv) (Thv) + trial), which corresponded to the 95% confidence interval of the single determination. The [la]b was measured at 15 and 30 min from the onset of exercise. The [la]b at 15 min (3.15 mmol.l-1, SEM 0.14) and at 30 min (2.95 mmol.l-1, SEM 0.18) were not significantly different in Th(v) trial. However, the [la]b of Th(v) + trial significantly increased (P < 0.05) from 15 min (3.62 mmol.l-1, SEM 0.36) to 30 min (3.91 mmol.l-1, SEM 0.40). These results indicate that Th(v) gives the [la]ss, max, at which one can perform sustained exercise without continuous [la]b accumulation.