Two weeks of high intensity inverval training (HIIT) produced vast improvements in many fitness markers. Aerobic capacity (VO2max) improved 13%, this is an incredible improvement in such a short time. Whole body fat oxidation increased 36% after HIIT training.
The subjects performed 10 four minute intervals at 90% maximum with 2 minute rest between intervals. 7 sessions were performed over the two weeks, so the training was probably performed every other day.
This is truly an impressive study. I’ve never seen any evidence that lower intensity exercise could duplicate these results in such a short time period.