A plyometric exercise is one that involves an eccentric contraction followed by an explosive movement of the same muscle. Plyometrics are performed to increase the ability of a muscle to generate explosive force, which in the case of the legs enables the athlete to jump higher and farther.
A squat jump requires no equipment. To perform a squat jump, set your feet shoulder-width apart. Squat down until your upper legs are parallel with the floor, then jump straight up into the air as high as you can. Concentrate on exploding into the leap.
A box jump requires a stable surface onto which you will jump. Use a box that will not slide out from under your feet. To perform a box jump, bend at the knees and leap onto the box. Step back off the box and repeat. Start with a low box and increase the height as you improve. This exercise can also be performed with one leg as an advanced variation.
Lateral Box Push-Offs
To perform a lateral push-off, find a box whose height causes your upper leg to be parallel to the ground when you stand beside the box and place one foot on top of it. Push off with the foot that's on the box, leaping laterally over the box and landing with that foot on the ground. The foot that was previously on the ground should now be on the box, and you will be on the opposite side of the box from where you started.
Burpees will help you get into position to explode into a leap much faster, as well as increase your endurance and work your upper body. To perform a burpee, squat all the way to the floor from standing position so that your hamstrings are pressed against your calves. Put your hands on the floor, and throw you legs backward into the pushup position. Perform a pushup, then return to the squatting position. Leap into the air and raise your hands overhead. Perform this sequence as quickly as possible.
To perform a box-depth jump, start on top of the box. Drop off to the ground. Don't jump; you are simply executing a controlled fall. The second you hit the ground, leap straight up into the air as high as possible. Your time spent on the ground should be as short as possible. Increase the height of the box to raise the difficulty.