Effects of Low-frequency High-intensity Interval Training on Cardiorespiratory Function during High Intensity Exercise in Athlete

Abstract

In a previous study, we found that once weekly high-intensity interval training (HIIT) for 8-12 weeks in normal healthy subjects increased maximal oxygen uptake (V_O2max) by 6-13% and prolonged maximal exercise duration by 33-89%during high-intensity exercise. Moreover, the effects of HIIT were reported to be more pronounced and specific during more high-intensity exercise at 90%maximum work rate (WR_max) and maximal exercise than during high-intensity exercise at 80% WR_max. However, it is unclear whether comparable effects are observed in athletes who perform intense exercise on a daily basis. The purpose of this study was to examine the effects of once weekly HIIT on cardiorespiratory function and exercise performance during maximal and submaximal exercises in college athletes. Seven male college student athletes participated in the study. Cardiorespiratory function was investigated by an incremental maximal exercise test and two constant step exercise tests, before and after the HIIT program. For HIIT, the subjects performed cycle ergometer training once a week for 2 months. The training consisted of three bouts of exercises at 90%maximum work rate to volitional fatigue. Significant increases in V_O2max (+12%, p=0.003) and maximal work rate (+16%, p<0.001) during the ramp exercise test were observed after HIIT. Maximal time to volitional fatigue during high intensity step exercise test was also significantly prolonged after HIIT (+72%, p=0.01) . Heart rates during exercise at both intensities were reduced significantly after HIIT compared to before HIIT, but oxygen uptake and minute ventilation measured over the same time interval did not change during high-intensity exercise. Regardless of the individual difference in initial V_O2max among subjects, the same improvement in V_O2max was obtained after HIIT, and the rate of increase in maximal exercise duration correlated with the rate of increase in V_O2max (γ=0.904, p=0.005) . In conclusion, short-duration once weekly HIIT improves cardiorespiratory function and exercise performance during maximal exercise in athletes, and the effects are more pronounced and specific during exercise at higher intensities. These findings will contribute to the development of new and optimal exercise programs for various age groups and physical conditions, including competitive athletes.