i have been doing this lately, good cardio workout and is a great fat burner
each is a 10 minute session,will really fuck you over]
to begin- use an exercise bike, warm up for the first 6 minutes by selecting a moderate level and go at a moderate pace. for the last four minutes you start each minute by going flat-out as fast and as hard as you can go for the first 15 seconds before going moderstely for the other 45 seconds.
then use the rowing machine, again choose a moderate level to go at and for 10 minutes go as fast and hard as you can go for 20 seconds then slow down to a moderate speed for 40 seconds. do this for the full 10 minutes.
then (the real killer) get on the treadmill-again its 10 minutes, except this time you run flat out for 2 minutes, then moderately for 2 minutes,etc...
finally get on the crosstrainer and just go at a moderate pace for 10 minutes ( you should be blowing ut of your arse by now)
works a treat especially if you are trying to build up your cardio-fitness and stamina