Supertraining, 2006, 6th edition, Mel C. Siff, Denver, Colorado USA
Lisa Ericson¹s System of Non-Impact Plyometrics
In the west, plyometrics (powermetrics) have become synonymous with depth jumps and medicine ball throwing, in other words, with activities involving impulsive contact between the extremities of the body and the ground or some object. Even in Russia, the birthplace of scientific plyometrics, the emphasis has been almost entirely on actions which exert some form of impact loading on the body. It may also be stated that all running, jumping and other ballistic actions involve a phase of polymeric activity, so that shock contact of parts of the body with some surface would appear to be the common denominator underlying all plyometrics.
However, this is not the only way of producing polymeric action. As discussed earlier, all polymeric drills so far used in the athletic world are of the impact variety. The existence of the non-impact variety was recognized when the author used a force plate to analyze biomechanical martial arts movements and the seated fitness for her seated aerobics¹ classes, which she developed after becoming paralyzed. A former professional figure skater and classically trained pianist, she developed a system of exercise rehabilitation which can produce very significant improvements in motor control, strength and hypertrophy without the use of weights or any other resistance apparatus.
After years of experimentation with different training methods, she has managed to gain recognition for her work and for several years has been teaching her seated fitness class to spinal patients at the renowned Craig Rehabilitation Hospital in Denver, as well as to regular aerobics clients at other athletic clubs in that city.
What distinguishes her exercise routines from normal aerobics is that she often uses very rapid wide-range movements choreographed at rates exceeding 200 beats per minute, interspersed with rhythmic transitional PNF-type patterns, offered over a session which characteristically lasts for 60 minutes. After an extended warm-up to ensure that the arms and body are adequately prepared for the main, high-intensity phase, the subsequent movements are initiated and terminated explosively in sets of uninterrupted sequences which regularly change their form and direction to avoid excessive fatigue, habituation or injury.
This system recruits the mitotic stretch reflex dynamically and powerfully in agonistic and antagonistic muscles over as large a range of movement as possible. The use of patterns, deliberately deviating in space and timing from those recommended by PNF and Pilates practitioners, cause pronounced overflow to adjacent muscles and speed up the rehabilitation of spinal patients, a phenomenon that has attracted the attention of medical specialists.
Ericson¹s system may best be categorized as non-impact plyometrics (non-impact powermetrics) because it obeys all the requirements of plyometrics as originally conceived by Russian scientists. True polymeric activity involves a ballistic action which is rapidly terminated by eccentric and explosive isometric muscle contraction, followed immediately by powerful concentric recoil mediated by recruitment of the mitotic stretch reflex, and augmented by the release of elastic energy stored in the connective tissues of the muscle-tendon complex.
The system developed by Ericson is reminiscent in many ways of some of the training methods used in karate which involve explosive snap punches, blows and kicks, or some boxing training drills such as shadow boxing or speed ball. In karate, the limbs are thrust powerfully outwards and then drawn back in a whip-like action, ready for the next repetition. In the martial arts, the number of repetitions are relatively few in number and separated by very brief intervals between them, whereas the Ericson system used many repetitions without pause. The karate punch is rarely whipped back immediately, but makes contact with its target for a very short period, which is sufficient to dissipate much of the elastic energy stored in the connective tissues. The transition phase between eccentric a and concentric phases in the Ericson system is usually shorter than that in karate and therefore, maintains high levels of muscle tension for prolonged periods. The shorter transition phase and the greater number of continuous repetitions in the Ericson system probably explains the differences in functional and structural development produced by it compared with the karate system.
The implications of the Ericson seated aerobics¹ system for sports training are great. Traditional polymeric drills have often been criticized because they all involve high impact forces produced during explosive contact of parts of the body with some surface or object. The Ericson system eliminates the need for impulsive contact width a hard surface and drastically diminished the intensity of shock waves transmitted to the joints and entire musculoskeletal system by explosive two-way movements.
Most of the Ericson movements offered in the average fitness class more accurately would be classed as sub maximal plyometrics, just like the more usual repetitive drills over obstacles or with medicine balls. Performed in the form of all-out single movements, they become maximal non-impact plyometrics. Since depth-jumps involve the projection of the entire mass of the body, maximal impact plyometrics will generally increase muscle tension to a greater extent than the equivalent non-impact movements for the leg and hip extensors (e.g. the karate thrust-kick).
Nevertheless, maximal non-impact plyometrics, like submaximal impact plyometrics can serve as a preparatory tool for maximal impact plyometrics, for enhancing other functional and structural qualities or for selectively offering polymeric training to certain muscle groups instead of unnecessarily stressing the entire musculature. These qualities may include strength, muscle hypertrophy, muscle endurance and speed-strength endurance. To date, research into plyometrics has devoted most of its attention to increases in speed-strength (power), rather than these other qualities, so that preliminary studies executed in 1995 by University of Pretoria physiotherapy students supervised by Siff and Ericson warrant more detailed expansion.
Meanwhile, the significant increases in strength, speed-strength endurance and hypertrophy (which are not simply a result of propelling their wheelchairs) achieved by Ericson and her wheelchair athletes emphasize that there is still much more to be discovered about the methods and consequences of the different types of resistance training. Up till now, it has been considered fairly accurate to state that strength and power are best achieved by few repetitions of high-intensity exercises, whereas hypertrophy is best produced by medium numbers of repetitions with 65-85% of one¹s IRM. Ploymetric exercise traditionally fits into this scheme as a means of enhancing speed-strength.
From the changes observed in Ericsons¹s students, it would appear that even plyometrics should be examined in the context of the nature, duration and pattern of sets and repetitions, since it may be used to enhance fitness qualities other than speed-strength alone. Her system of non-impact plyometrics offers a safe addition to the fields of sports plyometrics and popular aerobics. It is potentially beneficial to any athletes who require high levels of upper body power and endurance, and vastly expands the somewhat uninspiring repertoire of arm rehabilitation techniques, generally offered to injured clients or spinal damaged patients in conventional physiotherapy. The aerobics world has erroneously labeled some rapid landing and jumping movements as aerobic plyometrics, but the latter, unlike the Ericson¹s movements, in no way comply with the definition of classical plyometrics. It is apparent that the aerobics community, as well as strength conditioning coaches, have a great deal to learn from an innovative non-impact polymeric training system developed by a creative athlete in a wheelchair.