For my 4x4 high intensity training (HIIT), I did 4 minutes of all out exertion on an elliptical followed by 4 minutes of rest. Do that four times. You can do this on a bike, running, swimming, etc.
For my 4x4 high intensity training (HIIT), I did 4 minutes of all out exertion on an elliptical followed by 4 minutes of rest. Do that four times. You can do this on a bike, running, swimming, etc.