Plyometrics refers to the concept of increasing the force of concentric contraction by preceding it by overloading an eccentric contraction.
Last updated on October 08, 2019
European strength athletes have used the principles of plyometric training for years in an effort to increase power (in this sense, literally, force x velocity). Such exercises can be made applicable to both Olympic and powerlifters or any activity where great amounts of explosive forces are required. Plyometrics refers to the concept of increasing the force of concentric contraction by preceding it by overloading an eccentric contraction. The idea behind the concept is to utilize the stretch reflex. The stretch reflex merely infers that a muscle will contract more forceably if it is immediately proceeded by a quick stretch in the opposite direction from which it usually contracts. This stretch usually amounts to a short, quick, forced eccentric contraction. This facilitation of a muscle contraction by the use of a quick stretch is a known physiological fact. Plyometrics seeks to expand upon this by not only using a stretch reflex but by forcing the muscle to work and be loaded eccentrically before it contracts concentrically.
Way back in the mid 70's Olympic lifting coach Carl Miller was a big advocate of using such drills, strongly favoring the European drill of bounding for speed and distance. When bounding, the quadriceps are forced to contract eccentrically to decelerate the body (otherwise you would simply collapse at the end of a bound). Then, the muscles must reverse the eccentric work and contract vigorously in a concentric manner to propel you into another bound. Part of the theory professes that this rapid transition of eccentric to concentric work develops power by forcing the muscles to develop their intramuscular cross-bridges faster. This process is one of the most important factors in generating muscle force.
As we understand plyometrics it would be best not to try and utilize the theory in conventional lifting, but to use drills during the off-season to develop better explosive action in the muscular system (within the limits that inherent genetic power can be enhanced). In actuality, many of the lifts involve an eccentric work phase immediately prior to a concentric effort anyway (bench and squat, for instance).
When applying plyometric loading, keep in mind that many of the factors in eccentric work are just the opposite of the concepts involved in concentric work. With plyometrics, the faster a muscle is forced to lengthen, the greater the tension it exerts. This is because a stretch reflex must be a quick stretch and not slow or sustained. Rate of stretch, then, is of utmost importance. This is just the opposite of concentric contraction, in which case, the faster a muscle shortens, the less tension it can develop. This of course, says something for heavy, slow training for strength, as in powerlifting, Remember also, that strength will only result from a work load that is carried out at a greater intensity than the muscle is normally used to.
The best drills for developing explosiveness in Olympic and powerlifters would include the following:
1. Horizontal Bounding for speed and distance. This can be done off both legs and occasionally on and off one leg. These bounds should be explosive for short distances, such as up to 50 yards.
2. Sprinting backwards for distances, also up to 50 yards.
3. Depth Jumping. Drop down off either a 24 inch box (181 lbs. and over) or a 30 inch box (under 181 lbs.) land on the balls of the feet and jump vertically as high as possible on the rebound. Depth jumping should be done in the off-season, only once a week and should be discontinued if patella tendon problems develop.
In summary, plyometrics are drills that can be used by Olympic and powerlifters during the off-season to aid in the development of explosiveness. They should be done as an adjunct to regular training (weights). Depth jumps should be done only once a week and be discontinued if knee tendonitis develops.
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