The ventilatory threshold gives maximal lactate steady state

Summary The purpose of this study was to examine whether the ventilatory threshold (Th_v) would give the maximal lactate steady state ([1a]_{ss, max}), which was defined as the highest work rate (W) attained by a subject without a progressive increase in blood lactate concentration [1a]_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 theW atTh_v (W_Thv) was determined. The results of two-way ANOVA showed that the coefficient of variation of a singleW_Thv determination was 2.6%. Secondly, 13 men performed 30-min exercise atW_Thv (Th_v trial) and at 4.9% aboveW_Thv (Th_v + trial), which corresponded to the 95% confidence interval of the single determination. The [1a]_b was measured at 15 and 30 min from the onset of exercise. The [1a]_b at 15 min (3.15 mmol·1^–1, SEM 0.14) and at 30 min (2.95 mmol·1^–1, SEM 0.18) were not significantly different inTh_v trial. However, the [1a]_b ofTh_v+ trial significantly increased (P<0.05) from 15 min (3.62 mmol·1^–1, SEM 0.36) to 30 min (3.91 mmol·1^–1, SEM 0.40). These results indicate thatTh_v gives the [1a]_ss,max, at which one can perform sustained exercise without continuous [1a]_b accumulation.