Mixed
Six sessions of high-intensity interval training (HIT) over two weeks significantly improve maximal oxygen uptake (VO2peak) and endurance performance in previously untrained individuals, primarily through increased skeletal muscle mitochondrial content and respiratory capacity rather than cardiovascular adaptations.
If you are new to exercise, you do not need to spend hours on the bike. Performing just six sessions of high-intensity interval training over two weeks—consisting of repeated 60-second hard efforts with short recovery—can significantly boost your aerobic capacity and endurance. Focus on intensity rather than duration to see rapid results.
These results suggest that increases in mitochondrial content following six HIT sessions may facilitate improvements in respiratory capacity and oxygen extraction, and ultimately are responsible for the improvements in maximal whole body exercise capacity and endurance performance in previously untrained individuals.
Why this rating
Randomized controlled trial with objective physiological measures, though small sample size (n=16) and short duration limit generalizability.
Source
Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function
Robert A. Jacobs et al. · Journal of Applied Physiology · 2013
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