Response of ventilatory and lactate thresholds to continuous and interval training

The purpose of this study was to evaluate the effects of continuous and interval training on changes in lactate and ventilatory thresholds during incremental exercise. Seventeen males were assigned to one of three training groups: group 1: 55 min continuous exercise at ~50% maximum O₂ consumption (V̇O₂(max)); group 2: 35 min continuous exercise at ~70% V̇O₂(max); and group 3: 10 x 2-min intervals at ~105% V̇O₂(max) interspersed with rest intervals of 2 min. All of the subjects were tested and trained on a cycle ergometer 3 day/wk for 8 wk. Lactate threshold (LT) and ventilatory threshold (VT) (in addition to maximal exercise measures) were determined using a standard incremental exercise test before and after 4 and 8 wk of training. V̇O₂(max) increased significantly in all groups with no statistically significant differences between the groups. Increases (±SE) in LT (ml O₂.min^-1) for group 1 (569 ± 158), group 2 (584 ± 125), and group 3 (533 ± 88) were significant (P < 0.05) and of the same magnitude. VT also increased significantly (P < 0.05) in each group. However, the increase in VT (ml O₂.min^-1) for group 3 (699 ± 85) was significantly greater (P < 0.05) than the increases in VT for group 1 (224 ± 52) and group 2 (404 ± 85). For group 1, the posttraining increase in LT was significantly greater than the increase in VT (P < 0.05). We conclude that both continuous and interval training were equally effective in augmenting LT, but interval training was more effective in elevating VT. The marked dissociation between the changes in LT and VT after training in group 1 suggests that LT and VT are regulated by different mechanisms. Our results demonstrate that LT and VT cannot be used interchangeably as indices of training adaptations.