Plyometrics

Plyometrics: what is it?

The mechanism is elastic. When a muscle-tendon unit is stretched quickly and then shortens straight away, it returns stored elastic energy and triggers a reflexive contraction, producing more force than the muscle could generate from a standing start. The Soviet coach Yuri Verkhoshansky formalised this as the shock method, and depth jumps came out of that work. Everything after it - box jumps, bounds, pogo hops, medicine ball rebounds - is a variation on the same principle with different amplitudes and joint loads.

The stretch-shortening cycle

Three phases. The eccentric phase stretches the muscle-tendon unit and loads it elastically. The amortisation phase is the transition between stretch and shortening, and it is the phase that decides whether the exercise is genuinely plyometric: the longer it lasts, the more stored energy is lost as heat. The concentric phase releases what remains.

That makes ground contact time the key variable. A fast, stiff, short contact is plyometric training. A box jump where the athlete lands, settles, resets and then jumps again is a jump - useful, but it is training concentric power, not the stretch-shortening cycle. Coaches often distinguish fast SSC work, with contacts under roughly 250 milliseconds, from slow SSC work above that.

Prerequisites and progression

Landing comes before jumping. An athlete who cannot absorb a drop from a low box with a quiet, controlled, aligned landing has no business doing depth jumps, because the eccentric loads in high-intensity plyometrics are far greater than anything they will meet in a normal lift. Teach landing mechanics, then low-amplitude hopping, then progressively higher and more reactive work.

A reasonable strength prerequisite for the higher-intensity work is a solid squat relative to bodyweight and, more importantly, the ability to decelerate under control. Body mass matters too: the eccentric load in a depth jump scales with it, so a heavier client accumulates joint stress much faster than a light one at the same box height.

• Progress amplitude and reactivity, not just height.
• Land on a forgiving surface. Concrete is not a plyometrics floor.
• Program plyometrics fresh, before strength or conditioning work.
• Stop the set when contact time lengthens or landings get noisy - quality is the whole point.

Volume and frequency

Plyometric volume is counted in foot contacts, not sets and reps. Common coaching guidelines put beginners around 80 to 100 contacts per session, intermediate athletes somewhat higher, and advanced athletes higher again for low-intensity work - with high-intensity depth jumps counted much more conservatively, often in the tens rather than the hundreds.

Two sessions a week is enough for most athletes, separated by at least 48 hours, and the connective tissue adapts more slowly than the muscle does. That is the real limiter: an athlete can often handle the work aerobically and muscularly weeks before their tendons and joints have caught up, which is exactly how Achilles and patellar problems appear in over-eager plyometric programmes.

Who plyometrics are for

Anyone who jumps, sprints, changes direction or plays a field or court sport benefits directly. Runners benefit through improved economy and tendon stiffness, which is one of the better-supported reasons for a distance runner to lift and hop at all.

For general-fitness and older clients, the intent transfers even though the exercises should not. Low-amplitude hops, skipping, fast step-ups and light medicine ball rebounds train the same reactive quality at a fraction of the joint load - and reactive strength is precisely what determines whether someone recovers from a trip instead of falling.