hey man .. great start. .. atleast u can tell what he is doing
but i have a few issues with it. please dont take it that i am battering your animation. i'm not disney myself.
1. at the start u might want to anticipate him going up before having him go down. ( a bit of anticipation on top of anticipation)
2. i would break those joints a bit. (hands) they are way too straight throughout the animation. bend them a lil bit it will look more natural .. maybe u can read up on successive breaking of joints. (animation survival toolkit by richard williams) is the bible!
3. at the start when he is crouching down he seems to be a bit off balance.
4. when he is landing. you might want to put it in a straight contact pose. for more change within the action and to show the impact.
5. and i would work on the landing a bit. i feel its a bit unrealistic he needs to overshoot a bit or even step forward or something.
6. play with his spine a bit more.
thats all i can think of for now i'm a bit tired
.. again great start and keep it up man