When a horse jumps, the rider must follow the movement of the horse.
Let's look at that movement: First, the horse plants his front hooves
at his "takeoff point." All of his weight is on his forelegs and he may
duck his head.
Next, he brings his hind legs under, as close as he can to the forelegs
(but without kicking himself). This causes a "rubber band" motion of
his back; it pops the rider up much the same as in a posting trot.
Next, he rocks back and puts all of his weight on the hind legs. He
will push up with his forelegs; this lifts his upper body so that his
body will "point" up and over the jump.
Next, he pushes off with his hind legs. He'll begin tucking his
forelegs to go over the jump. He will stretch his neck forward so that
his body can curve as he goes over the jump. (When he lands, his head
will be looking down, not up!)
In the next movement, he will sail gracefully :) over the jump. You
should get a nice half circle (bascule) from the takeoff point to the
landing point. The horse will tuck his forelegs as his head and fore
goes over the jump itself, and will tuck up his hindlegs as his hind
end goes over the jump.
As he lands, the horse will extend his forelegs to take his weight. He
lands heavily on his forelegs; the pasterns extend quite a bit to take
the shock of landing. His neck is lowered, and his hind end is still up
in the air.
He'll bring his hind legs down, again close to his forelegs. As his
hind legs land, he'll bring his neck up and take weight on his hind
end.
Once his hind legs are on the ground, his forelegs leave the ground
again and he takes his first stride away from the jump.
The horse shifts his weight around a lot while he's jumping; if you're not
following his movement with your own body, you can get thrown around a
bit. Also, if you're off-balance, you may pull him off-balance too.
Usually you will learn to jump over low jumps, on a steady, experienced
horse who can compensate for you while you learn to balance.
I think it is good for riders to learn, at first, riding in two-point
for the whole jump. In two-point, you are off the horse's back. It is
easier to move with the horse, because you do not have to get into
two-point, "release" with the reins, and then sit again after the horse
lands.
Two-point means that you have your weight on two points (your two legs:
knees, calves, and heels) instead of three points (your two legs, and
your seat). To ride in two point, "stand up" in the saddle; take all
your weight in your legs and stick your rear end out behind you :)
"Fold" your torso a little--that is, lean forward from the hips. Make
sure your knee is still nicely bent. Your knee is the "shock absorber"
that allows you to follow the horse's movement.
While learning to jump in two point, you'll also have your hands about
halfway up the horse's neck. You can either grab the mane with both
hands, or rest your fists along the horse's crest (where his mane
grows).
You want lots of slack in the reins. As the horse jumps, he extends his
head and neck forward. If the reins are too short, then he doesn't have
room to move forward; he will reach the end of the reins and hit his
mouth on the bit. He will not be able to extend any more. He needs that
room to extend in order to have a nice "bascule"; if he can't extend
his neck, then his balance is compromised and he is punished (hitting
the bit) for trying to extend his neck. Alternatively, if he keeps
pulling, he may yank you off balance. Eventually you will learn to
follow the extension of his neck with your hands as you jump (moving
your hands forward and back). But while you are learning, just make
sure that there is lots of slack in the reins.
You'll go into your two-point position and approach the jump. When the
horse goes to jump, you need to simply maintain your balance with your
upper body. Lean forward a little as the horse goes up and over, and
get back in standard two-point as he lands.
Riding this way you can learn how it feels to go over a jump, before
you need to add actually going into two-point on takeoff and releasing
the reins. You will probably need someone to lead the horse, or lunge
the horse, while you are learning this way; while you have lots of
slack in your reins, you will probably need someone else to direct the
horse over the jump.
Part Two: Once you accustom yourself to
the feel of a jump in two-point, learning to ride the jump.