H.I.I.T. stands for high intensity interval training, and it’s one of the most efficient exercise modalities around.  Set a timer and let’s go! Start with :30 seconds hard work and :30 seconds rest.  As your fitness improves, shorten your rest interval to 20 or even 10 seconds.  Make sure you are going all out during the work intervals.  You should be feeling breathless and your heart should be PUMPING.  Now rest.  Rinse and repeat!