Dose-response relationship between interval training frequency and magnitude of improvement in lactate threshold

The purpose of this study was to determine if interval training at 110-120% of peak power output one and two days/wk in addition to habitual training would elicit improvements in lactate threshold (LT) in a dose response manner. Twenty physically active individuals completed this study: age--21.1+/-1.3 yr, height--172.1+/-7.4 cm, body mass--68.4+/-9.1 kg, VO (2)max--45.3+/-5.2 mL/kg/min; and were randomly assigned into two separate 6 wk training groups--either 1 day/wk interval training or 2 days/wk interval training at 110-120% of peak workload (from an incremental exercise test) on a cycle ergometer. After 6 wk, LT (% VO (2)max) increased significantly ( P<0.05) in both 1 day/wk (4.3+/-3.2%) and 2 days/wk (8.2+/-2.6%) groups. A two-factor mixed ANOVA identified a significant interaction between exercise frequency and LT (%VO (2)max) values ( P<0.05) indicating that LT responded differently to 1 day/wk and 2 days/wk of interval training. Findings from the present study show high-intensity, interval training to be a successful strategy for modifying this important metabolic threshold. Moreover, results suggest that there is a dose-response relationship between frequency of interval training and the magnitude of LT improvement.