I just did the toughest weight training ever. I believe it was so difficult to me b/c naturally i am very quick/fast/bouncy but my endurance is naturally poor. My coach used to do it in Indonesia. Basically you do weights but do 40 reps of each weight then 30. I would use about 60% of my max weight, but this is only the first time i've done the whole circuit. The point of doing these weights is to do them quickly as if you were working on footwork. I have never felt like puking after weights before... this is what I did: 40 reps, 30 reps half squat 40, 30 calf raises 40, 30 inclined squats 40, 30 leg extension Do all of these excercises quickly. The burning i felt was unreal, also the workout only takes 20-30 minutes including warm up! If you are naturally more fast twich fibers this workout will make you feel it! I was planning on doing 400m sprints today but there was snow on the ground. This IMO is harder and the natural high lags for 30-45 min afterwards!