Plyometric exercises are quick, powerful movements that literally put a spring in your step. You don't just walk: You jump. You bound. You leap. You skip. If you're an athlete, you need plyometric training to be able to react rapidly and safely on the playing field. Even if you're not a jock, the speed and strength you develop through plyometric exercises can help you lift your groceries or recover from a stumble more easily.
Plyometrics for Power
The word "plyometric" is derived from two Greek words. Plio means "more" and metric means "measure," so the word literally means "more measure." Although jumping and plyometric-type exercises have a long history, the term plyometrics was only coined in 1975, by American track and field coach Fred Wilt. The purpose of plyometric exercises is to increase the power of your muscles -- their ability to contract forcefully as quickly as possible.
Plyometric Muscle Actions
Your muscles stretch before contracting in plyometric exercises. For instance, to jump, you first flex your hips and knees, stretching your glutes, hamstrings and quads. Those same muscles then quickly contract to propel you into the air. Many upper body plyometric exercises involve catching a medicine ball thrown by a partner. As you catch the ball, your elbows bend to absorb the impact, stretching your triceps. Your triceps then contract powerfully, enabling you to toss the ball back to your partner.
The Stretch-Shortening Cycle
That rapid transition between your muscles stretching and contracting -- called the stretch-shortening cycle -- is the key to how plyometric exercises work to increase your power. As connective tissues in your muscles stretch, they store elastic energy. Like the rapid recoil of a stretched rubber band in a slingshot, your stretched tendons and fascia spring back quickly, enabling your muscles to contract more powerfully than they could without pre-stretching.
The Stretch Reflex
Plyometric exercises also stimulate your nervous system to create stronger muscle contractions. Receptors in your muscles sense when a muscle is being stretched. Those receptors send a signal to your spinal cord, which causes a reflex contraction of the muscle. The more rapid the stretch, the more powerful the contraction. This is the same reflex your doctor measures when she taps your knee with a hammer. The tap stretches the tendon of your quadriceps muscle, stimulating the stretch receptors. The reflex contraction of your quads causes your foot to pop up.
- Essentials of Strength Training and Conditioning; National Strength and Conditioning Association
- Therapeutic Exercise for Athletic Injuries; Peggy A. Houglum
- Human Anatomy and Physiology; Elaine N. Marieb
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