sportEX dynamics - 1999-2010

EXPLOSIVE TRAINING

running, kicking or throwing) involve the reflex/elastic properties of

the muscle-

tendon complex and are ballistic in nature, even when initiated from a static position. These elastic properties allow a stretch- shortening cycle to occur, this is where a muscle is forcibly and rapidly lengthened by a stretch or countermovement, then stretch receptors (muscle spindle fibres, golgi tendon organs) send signals to the central nervous system, stimulating concentric contraction of the involved muscles which then contract forcefully as elastic energy is released from the muscle fibres and connective tissue. This process is commonly referred to as a myotatic reflex, which forms the basis for all plyometric-training actions.

Training for maximum strength alone will not adequately train these elastic proper- ties within a muscle, therefore training for sports should not only encourage the inclusion of rapid stretch-shortening (plyometric) methods, but it should also incorporate frequent stretch-shortening cycles into training movements as much as possible to enable the athlete to produce maximal forces in training movements. The ‘amortisation’ or reactive phases of the stretch-shortening cycle (the transition phase between eccentric lengthening and concentric shortening) should be as short/rapid as possible. This is trainable within athletes who are subject to the correct coaching and training methods.

A stretch-shortening cycle can be observed in the most experienced lifters performing both the snatch and clean lifts, and it is this action that needs to be developed in athletes if the maximum benefits of the lift are to be carried over to

BOX 1 - GLOSSARY

■ Muscle-tendon complex = describes the interaction between muscle fibres and dense connective tissue that surrounds individual muscle fibres, bundles of muscle fibres and the muscle belly itself

■ Stretch-shortening cycle = when a muscle is forcibly and rapidly lengthened by a stretch (such as countermovement), stretch receptors (muscle spindle fibres and golgi tendon organs) to sense both the rate and amount of stretch within the muscle. When this stretch becomes rapid in nature, as a mechanism for injury prevention, these receptors initiate a rapid and forceful contraction of the stretch muscles through the central nervous system. This reflex contraction utilises potential and elastic energy that has been stored in the muslce fibres and connective tissue. the muscle fibres and connective tissue

■ Amortisation or the reactive phase of the stretch-shortening cycle = the transition phase between eccentric lengthening and concentric shortening

■ Plyometric = bounding movements designed to stimulate stretch-shortening cycles. 16 www.sportex.net

sports performance (10). This stretch- shortening cycle occurs during the transi- tion phase immediately following the first pull, and is often referred to as the double-knee bend (DKB).

COACHING THE DOUBLE KNEE BEND Over time, many coaches have observed that the double knee bend ‘just happens’ in experienced lifters. It only ‘just happens’ when taught correctly. Although we could debate whether to teach or not to teach the double knee bend until we’re blue in the face, one thing is not debate- able, the fact that the DKB must happen if the lift is to be optimal. It is the optimal technique that is necessary to derive the benefits these lifts offer. Some coaches will say you can’t teach the DKB because it is stretch reflex. But why does this stretch reflex happen? If the first pull technique is executed correctly it will place the athlete in the proper position to elicit the stretch- shortening cycle - this certainly can, and should, be coached. Waiting for the athlete to ‘stumble’ upon the technique, as an ‘accidental phenomenon’ will only allow incorrect motor patterns to establish themselves. We are what we repeatedly do, therefore proper technique should become a habit rather than an ‘accidental phenomenon.’

It is hard to imagine taking the same approach when teaching a squat, where many athletes find a full range of move- ment hard while keeping their heels on the floor. Do we just allow them to squat on their toes because they are not able to execute the proper technique right away? How about a gymnastics coach taking the same approach to coaching a hand-spring

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