honestly Intensive is the best way of training you don't need the others I train during GC's and have won games at 60% health before today stupid I know but thats sweet nitro for you .
to answer your question on training
stretching takes a little of your health away 3% to be precise takes just over 30 mins to recover unless you use your health kits itis easy to recover from but you won't progress in terms of getting training points fast with the stretching
Cardio takes up 2 hrs and 15% of your health you get a little in training points
intensive takes at least 4 hrs and 36% of your health but you will get the most training points for your team if you do intensive