How Plyometrics Works

The basis of plyometric exercises is that they toughen muscles and condition nerve cells, which trigger a pattern of muscle contractions. Specifically, the exercises engage the myotatic reflex -- the release of power -- when muscles are stretched to their maximum. This reflex in turn stimulates neurons called stretch sensory receptors. The ultimate goal is achieving as strong a muscle contraction as possible in the shortest amount of time possible. Plyometrics uses a key concept of exercise science: Muscle contractions that last the least amount of time produce more energy than a slower contraction or release regardless of the size or bulk of the muscle.

Another key element of plyometrics is concentric contraction. For a muscle to act, it first must "coil up," which is actually stretching out to its maximum pre-action length. This loads the muscle, like cocking a gun. Then, as the muscle is held in this state, energy is stored, and energy grows as the muscle is held. That brief storage -- lasting a second or less -- allows for maximum storage and use of the energy.

There are three phases of the plyometric muscle contraction. The first is the eccentric phase, the rapid muscle-lengthening movement -- that initial stretch or loading action. Next is the amortization phase, the very brief, power-building period of muscle rest or holding period. Finally comes the concentric phase, in which muscles are released to create the explosive muscle shortening movement. It's the big payoff.

There's also a neurological component: Plyometrics train the brain to treat muscles differently, to the athlete's advantage. The brain is hardwired to limit force when a muscle is stretched out; the brain tells the muscle to hold, and the muscle can waver slightly, resulting in a loss of energy as it's slowly released in a series of small contractions. Plyometric exercises can condition the brain to tell the muscles something different -- they train neurons to learn that in sports situations, the needs of a muscle are quick muscle contractions and precise, powerful, singular releases that produce a surge of energy.

Read on to learn about the benefits and risks of plyometrics.

The benefits of plyometrics are the simple but elusive athletic needs of more speed, more stamina and more power, be it in running, jumping, throwing, swimming or another sport-specific movement. It's about the efficient use and manipulation of muscles to produce consistent peak performance, not about building bulkier muscles.

These benefits come with practice, training and care. These exercises take competitive athletes who want a permanent, physical edge to the next level of competition by teaching their bodies to do what they want them to do. To attempt a plyometrics routine, you've got to already be in shape. While sometimes used to build muscle back as part of rehabilitation or physical therapy, plyometrics are still primarily for use by athletes who are in training and are already strong, fit and flexible. Flexibility prevents injury, while also ensuring that the plyometrics are used to their peak efficiency. It also helps to be strong and currently engaged in a strength-building routine. Can you back-squat (lifting with the bar of the weight held behind you at the base of your neck) double your bodyweight? Then you're suited for lower-body plyometrics. If you can bench-press your bodyweight, you're ready to try upper-body plyometrics.

While plyometics injuries aren't common, they can happen. If you attempt, say, a jumping exercise from too high, you can land wrong and twist an ankle. Even if you're doing everything right and under the guidance of a trainer, don't overwork your muscles if they feel too tender, because that can lead to tears. A proper exercise surface is important, too. It's best to avoid using a concrete or gym floor. Instead, train on soft ground or gym mats, which absorb the shock of plyometrics.

What are some plyometric exercises you can try? Check out the next page.

Plyometrics may look like simple exercises, but they are part of a precise and advanced training system, so seek out a trainer before you begin a regimen in earnest. Success can be ensured -- or at least enhanced -- with proper sports nutrition, too. And when you start, don't do too much too fast. Plyometrics should be performed no more than three to four times a week (for 10 to 15 minutes at a time) at first to properly train muscles and neurons. It's a gradual process to change the hardwiring of your brain and muscles.

Plyometrics is a mid-workout activity. You should have already done some basic but thorough stretching, aerobic exercise and/or weight training before the session. You should be very loose and very mobile.

Here are some examples of plyometric routines which are simple and even fun:

Slalom jump -- Stand with your feet together on one side of a line. Jump over the line from side to side, repeatedly, with your feet held together.

Depth jump -- Stand on a raised platform approximately 2 to 3 feet (61-91 centimeters) above the ground. Step off with one foot, then the other, then immediately jump straight up.

Vertical jump -- Stand with your feet hip-width apart, hands on hips. Tilt your hips back, bend your knees, and then immediately leap straight up. Land with your feet in the same place they started.

Ankle hops -- Balance on the balls of your feet, with your heels slightly elevated and your feet about hip-width apart. Bend your knees, place your hands on your hips, and repeatedly hop forward, pushing off with and landing on the balls of your feet. Keep bouncing along, spending almost no time on the ground (hit the ground, leap), never letting your heels or toes hit the surface. Then do it backward.

Plyometric push-up -- Get into your usual push-up position then lower yourself. Now, push up quickly and forcefully so that your hands leave the ground. Catch your fall with your hands.

Explosive start throws -- Stand with your feet at hip-width and with your knees slightly bent. Pick up a medicine ball to chest level, then immediately push yourself up to stranding straight and push the ball out forward. As you push the ball forward, heave your body into a spring of a few steps. Keep repeating, alternating which foot you push out with.

To see more speed training articles, check out the next page.