Adaptations to training at the individual anaerobic threshold

Summary

The individual anaerobic threshold (Th_an) is the highest metabolic rate at which blood lactate concentrations can be maintained at a steady-state during prolonged exercise. The purpose of this study was to test the hypothesis that training at the Th_an would cause a greater change in indicators of training adaptation than would training “around” the Th_an. Three groups of subjects were evaluated before, and again after 4 and 8 weeks of training: a control group, a group which trained continuously for 30 min at the Th_an intensity (SS), and a group (NSS) which divided the 30 min of training into 7.5-min blocks at intensities which alternated between being below the Th_an [Th_an−30% of the difference between Th_an and maximal oxygen consumption ($\dot VO_{2 max}$)] and above the Than (Th_an + 30% of the difference between Th_an and$\dot VO_{2 max}$). The$\dot VO_{2 max}$ increased significantly from 4.06 to 4.271 · min⁻¹ in SS and from 3.89 to 4.061-min⁻¹ in NSS. The power output (W) at Th_an increased from 70.5 to 79.8%$\dot VO_{2 max}$ in SS and from 71.1 to 80.7%$\dot VO_{2 max}$ in NSS. The magnitude of change in$\dot VO_{2 max}$,W at Th_an, %$\dot VO_{2 max}$ at Th_an and in exercise time to exhaustion at the pretraining Th_an was similar in both trained groups. Vastus lateralis citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities increased to the same extent in both trained groups. While all of these training-induced adaptations were statistically significant (P<0.05), there were no significant changes in any of these variables for the control subjects. These results suggest that the relative stimulus for physiological adaptation to training was similar in SS and NSS. These results also demonstrate that, when training intensity is set relative to the Th_an, it is the mean intensity during training that determines the extent of adaptation regardless of whether the exercise is performed intermittently or continuously.