When my time in sispec...
This guy was jumping 205cm in SBJ...
My OC told him " You go run 1 round parade square!"
When he came back, OC say "jump again!" We though he so shack liao how to jump...
This time he jump an amazing 230cm !!
ONly from that result, then i notice OC was not actually punishing him.. running really warm up our muscles... therefore, it is better to do some running on the spot, tuck jumps.. before SBJ...
If your shuttle run come before SBJ... good for you! if not then do some warm up exercises... SBJ is all about explosive power...
So try the power jump method suggested by the others.. or you can try execises that involve quick and explosive muscle movements... But always remember to warm up before....
And 7 hrs of uninterrupted sleep !!