i hated this one in juniors , but it is still in my routine almost 20 years later.
i put a milk crate on the floor and do lateral jumps over it for a minute. (you know side to side with your feet together) ......in the old days it was the weight bench ...sigh....
for the second set i carry 15 lbs. in each hand and do another minute of jumps.
third and last ( unless i'm feeling saucy) i jump for two minutes with no weights.if i'm still in the mood, i grab the weights again and jump until i'm done. this excersise helps the lungs , the calves, and at the same time helps with footspeed.
(that after a real light strength workout, bench press light weights many reps,good mornings light weight many reps, and some light shoulder work again light weight many reps. should help. hell i'm still playing with the twenty somethings well into my thirtys and they dont laugh.)
sounds easy, but it will help with your stamina and leg strength.
remember, keep the feet together and try to bend the knees while youre in the air and keep your shoulders as still and level as possible. up the height of the obstacle and /or the amount of jumping for desired effect.
and remember ... always drink tons of water.