Effects of 4 Weeks High-Intensity Training on Running and Cycling Performance in Well-Trained Triathletes

Abstract

Introduction: The aim of this study was to investigate the effect of a 4 week high-intensity interval training (HIIT) program on running and cycling performance. HIIT is a training method which can be used to improve physical fitness in less time, and reduced training volume, than traditional endurance training. HIIT allows athletes to accumulate time at higher training intensities, which is difficult to achieve when training in a continuous method.
Methods: Twelve well-trained triathletes completed 4 traditional training weeks as a control period. They were then randomly assigned to a bike or run HIIT program completing 2 HIIT sessions each week. A 20-minute cycling time trial and maximal aerobic power test on the treadmill were measured before and after the HIIT program.
Results: Both bike and run HIIT group achieved an increase of 6.7 and 2.1% in velocity at 2 mM and a decrease of 6.4 and 8.4% in the HR variable at 2 mM, respectively. Velocity peak decreased 1.9% in the run HIIT group and 1.8% for HR at 4 mM. Velocity peak decreased ~2% in the bike group and maintained HR maximum while there was a small reduction in the run group. For cycle time trial, the bike HIIT group demonstrated a significant improvement in average velocity (8.8%), whereas, velocity was slightly lower in the run training group (-3.5%).
Conclusion: A 4-week bike HIIT program improved running performance in moderate to well trained triathletes. However, in our study, the cycle performance was not enhanced by a 4-week HIIT running program, this may be due to the accumulated fatigue for the run group subjects.