Next time you watch a basketball or volleyball game, notice how high the athletes jump to block a shot or spike the ball. Ever wonder if you could jump as high?

Stand next to a wall with a short pencil in your hand and hold your arm as high above your head as you can, keeping your feet flat on the floor. Make a mark on the wall to note your standing reach. Then jump as high as you can, keeping your arm high above your head. At the top of your jump, make another mark on the wall. It works best to stand close to, but not touching, the wall when you jump. The difference in height between the two marks is a measure of how high you jumped.

You may be able to jump higher if you change how much you bend your knees before jumping. As you straighten your knees, you push your feet harder into the floor, which allows you to push off the ground with more force and jump higher. If you don't bend your knees much, you don't get much extra push. On the other hand, a deep crouch overstretches the thigh muscles, making them less efficient in pushing you off the ground. Experiment to find the amount of knee bend that gives you the most height.

Swinging your arms up can also add to your jump's height. As your arms swing up, your body is forced downward in reaction, increasing the force with which you push off the ground, and, therefore, the height of your jump. To be effective, your arms must finish their upward motion before your feet leave the ground.

This method of measuring a person's vertical jump is known as a Sargent jump, after Dudley Sargent, one of the pioneers in American physical education. When he studied a group of college students early in this century, he found that, on average, they jumped about 20 inches. There are no official records for a jump like this, but in 1976, basketball player Darrell Griffith's standing vertical jump measured four feet!