http://www.tabataprotocol.com/

Try to workout (weight lifting/running/push ups etc...) against time and with a Gymboss or a clockwatch!

The best is to work with the Tabata protocol = 8 intervals of 20 seconds all-out intensity exercise followed by 10 seconds of rest

Yo can change the timing if you want =i lift weight during 30 secondes and rest 30 others...........The results = you work your mental power+you work your heart+you work more than when you want to do X reps and X set.......

Of course you have to decrase the weight to do this................

Try this!!!