Eur J Appl Physiot (1991) 63:55-59

Applied Physiology European Journal of

and OccupationarPhysiology © Springer-Verlag1991

The ventilatory threshold gives maximal lactate steady state Yoshiharu Yamamoto 1, Mitsumasa Miyashita 2, Richard L. Hughson 1, Shin-ichi Tamura 2, Minoru Shinohara 2, and Yoshiteru Mutoh 2 1 Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 2 Laboratory for Exercise Physiology and Biomechanics, Faculty of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, 113 Accepted February 1, 1991

Summary. The purpose of this study was to examine whether the ventilatory threshold (Thv) would give the maximal lactate steady state ([la]. . . . . ), which was defined as the highest work rate (IV) 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 (Wa-hv) 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 30min exercise at Wa'hv (Thv trial) and at 4.9% above I)¢'Vhv(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.1-1, SEM 0.14) and at 30 min (2.95 mmol.1-1, SEM 0.18) were not significantly different in Thv trial. However, the [la]b of Thv + trial significantly increased (P 0.05) while the between subjects F-value was significant (P 0.05) different. The set intensity for T h v + trials was 162.7 W, SEM 31.0, representing 104.9% of 155.1 W, SEM 29.6. Table 2 shows the individuals values and Fig. 4 shows the group means of [la]b at the onset, the 15th min, and the 30th min o f constant intensity exercise in Thv and Thv + trials. Although we terminated the r a m p exercise tests as soon as possible, some subjects still showed relatively high values for baseline [la]b (Table 2). Therefore, in this study, we focused on intra-individual changes in [la]b between 15 and 30 rain of exercise. The m e a n [la]b at 15 rain (3.15 m m o l . 1 - 1 , SEM 0.14) was not different from that at 30 rain (2.95 m m o l . 1-1, SEM 0.18) in Thv trials. However, [la]b o f Th V -1- trials significantly increased ( P < 0,05) from 15 rain (3.62 m m o l . 1 - 1 , SEM 0.36) to 30 rain (3.91 retool.1-1, SEM 0.40).

58 Table 2. The individual blood lactic acid values (mmol.1-1) in

study 2 Thv Subject

Thv+

Rest

15 min

30 min

Rest

15 min

30 min

1.3 2.6 1.9 1.8 1.6 1.3 1.3 1.1 2.6 2.4 1.0 3.1 1.9

3.6 3.3 3.3 3.4 2.5 3.0 2.9 2.8 3.3 3.9 2.2 4.0 2.7

3.3 2.8 2.7 2.7 2.3 3.0 2.2 3.2 2.2 2.8 2.4 4.5 3.3

1.5

4.1

2 3 4 5 6 7 8 9 10 11 12 13

2.2 1.2 1.2 2.2 2.4 0.8 1.2 1.3 2.2 1.0 2.2 1.0

3.9 2.5 2.4 2.8 4.7 2.4 3.0 2.4 6.1 2.2 5.7 4.8

4.2 4.1 3.0 2.1 3.1 5.1 3.1 2.9 2.5 6.5 2.4 5.6 6.2

Mean SEM

1.84 0.28

3.15 0.14

2.95 0.18

1.57 0.16

3.62 0.36

3.91" ** 0.40

1

* P