The ventilatory threshold gives maximal lactate steady state.
The purpose of this study was to examine whether the ventilatory threshold (Thv) 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 Thv (WThv) was determined. The results of two-way ANOVA showed that the coefficient of variation of a single WThv determination was 2.6%. Secondly, 13 men performed 30-min exercise at WThv (Thv trial) and at 4.9% above WThv (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 Thv trial. However, the [la]b of Thv + trial significantly increased (P less than 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 Thv gives the [la]ss, max, at which one can perform sustained exercise without continuous [la]b accumulation.
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Y
Y
Yamamoto
M
M
Miyashita
R L
RL
Hughson
S
S
Tamura
M
M
Shinohara
Y
Y
Mutoh
D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007773:Lactates / Q000097:blood*; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption; D012119:Respiration / Q000502:physiology*
D007773:Lactates; D019344:Lactic Acid