4 minutes run hard enough to push heart rate to 90%, 3 minutes recover, repeat 4 times; about 45 minutes, every other day if you're old and need the recovery.

4 minutes run hard enough to push heart rate to 90%, 3 minutes recover, repeat 4 times; about 45 minutes, every other day if you're old and need the recovery. https://www.ntnu.edu/cerg/advice https://www.ntnu.edu/cerg/advice https://vimeo.com/75764170 https://vimeo.com/75764170