Lengthy research into ways of developing explosive strength and reactive ability lead to the development of the so-called ‘shock’ (plyometric) method. Essentially, it consists of exciting the muscles by means of an unexpected stretch preceding any voluntary effort. Kinetic energy and not particularly heavy loads should be used for this, where the kinetic energy may be amassed by means of the body or loads plummeting from a certain height. Depth jumps and medicine ball rebounding are two of the exercise regimes ordinarily used in plyometrics. The ‘shock method’ means exactly that: a method of mechanical shock stimulation to force the muscle to yield as much tension as possible. This method is categorised by spontaneous action of marginal duration between the end of the eccentric braking phase and start of the concentric acceleration phase. It depends on the production of a very short-lived explosive-isometric and eccentric-isometric phase which heralds the discharge of the elastic energy stored in the tendons and other components of the series elastic component of the muscle complex during the eccentric braking phase. If the shift phase is extended by more than about 0.15 seconds, the action may be considered to be ordinary jumping and not classical training plyometrics. Practical application of the plyometric method entails taking certain measures. For starters, the range of motion should be to some extent greater than the obligatory coordination range of the exercise in order to augment shock absorption by the soft tissues and in that way elude impact injury. Moreover:
- The amortisation phase should be of minimal duration, but enough to create spontaneous contraction of the muscles.
- The plyometric training should be preceded by a thorough warm-up of the intensively involved muscles.
- As a preliminary guideline, the prescribed amount of plyometric exercises should not surpass 5 to 8 repetitions in one set.
- One should try to upturn the speed and acceleration of movement before increasing the drop height or take-off height.
- Rest periods are vital for the operative and safe use of plyometrics. The rest interval between sets of maximal plyometric exercises should be roughly 10 minutes for power improvement (strength-speed and speed-strength) and much shorter breaks with submaximal plyometrics to progress explosive-strength endurance.
• Verkhoshansky, Natalia Verkhoshansky.Special strength training: manual for coaches. S.l.: Verkhoshansky Sstm, 2011.
• Verkhoshansky, Yuri Vitalievitch, and Mel Cunningham Siff. Supertraining. 6th ed. – Expanded ed. Rome, Italy: Verkhoshansky; 2009.