What is Plyometrics?

What is Plyometrics?

Plyometrics is training built around one idea: load a muscle-tendon unit eccentrically right before it fires concentrically, so the muscle rebounds off stored tension instead of starting from a dead stop. The name comes from the Greek plythein, to increase, combined with metric, to measure. American track coach Fred Wilt coined the term in 1975 to describe a method Soviet sport scientist Yuri Verkhoshansky had already been using with jumpers and sprinters since the 1960s, which Verkhoshansky himself called the shock method because the athlete drops from a height and absorbs a jarring impact before rebounding upward.

Classic plyometric exercises include depth jumps off a box, box jumps onto a platform, bounding series, hurdle hops, and, for the upper body, plyometric push-ups and medicine ball slams or throws. Track and field coaches, basketball and volleyball programs, soccer and American football strength staffs, and general lifters all use some form of it, because the goal is always the same: teach the nervous system and the muscle-tendon unit to produce force fast, not just produce a lot of force. That distinction matters because a heavy back squat and a depth jump can move similar loads relative to bodyweight yet train completely different qualities — one builds maximal strength over roughly a second, the other builds the ability to express force in a fraction of that time.

How it works

Every plyometric rep has three phases: an eccentric phase where the muscle-tendon unit lengthens under load (the dip into a countermovement, or the landing off a box), a brief amortization phase where the movement transitions from lengthening to shortening, and a concentric phase where the muscle contracts explosively to produce the jump, throw, or sprint push-off. The amortization phase is the whole game.

Verkhoshansky originally defined a true plyometric contraction as one where that transition lasts under 0.10 seconds; because that is hard to measure on the field, coaches instead classify movements by total ground contact time. A fast stretch-shortening cycle keeps ground contact under roughly 250 milliseconds, the range seen in sprinting, low hurdle hops, and low-box depth jumps, and it relies on elastic energy stored in the Achilles and patellar tendons plus a contribution from the stretch, or myotatic, reflex.

A slow stretch-shortening cycle runs 250 milliseconds or longer, as in a countermovement jump from a deep squat, and behaves more like a standard strength movement with less elastic energy return. The longer the amortization phase runs, the more of that stored elastic energy dissipates as heat instead of adding to the next concentric push, which is why sloppy, slow landings blunt the training effect even when the jump still gets the athlete off the ground. This is also why coaches obsess over quiet, fast landings: the shorter and stiffer the ground contact, the more of the eccentric energy comes back out as power.

The formula

Reactive Strength Index (RSI) = jump height (m) ÷ ground contact time (s)

An RSI of 2.0 or higher is a commonly used benchmark for well-trained field-sport athletes on a drop jump test; elite sprinters and jumpers often exceed 3.0. Ground contact under 250 ms is a fast SSC; 250 ms or longer is a slow SSC with a different training effect.

Types

Worked example

A conservative eight-week on-ramp for an athlete new to jump training, moving from landing mechanics to a genuine fast stretch-shortening cycle stimulus. Foot contacts, not just sets and reps, are the volume unit coaches track week to week.

Stop a set the moment landings get loud, ground contact visibly lengthens, or knees start to cave; those are signs the nervous system is fatigued and the rep is training compensation, not power. Full recovery between reps (roughly 45 to 90 seconds) protects intent and speed.

Plyometrics vs ballistic training

Most power programs use both. A depth jump trains the rebound off an imposed stretch; a loaded jump squat or med ball throw trains raw concentric drive with no landing constraint. Programming them together covers more of the force-velocity curve than either alone.

By goal

• Team-sport and track & field athletes: Run 2 to 3 sessions a week at 80 to 140 foot contacts per session in the off-season, tapering volume and keeping only the highest-intensity, most sport-specific jumps (bounds for sprinters, lateral bounds for cutting sports) as competition approaches.
• General fitness and conditioning: Add 1 to 2 short plyometric finishers a week, such as jump rope, squat jumps, or low box jumps, for conditioning, bone density, and rate of force development. Keep intensity moderate and stay strict on landing mechanics rather than chasing fatigue.
• Rehab, return-to-play, and older adults: Start with low-amplitude, bilateral, sub-maximal jumps under supervision, and only introduce plyometrics after strength, balance, and squat-depth screening clear standard return-to-sport criteria. Systematic reviews show carefully dosed lower-limb plyometrics are well tolerated even in older adults.

Common misconceptions

• "Any jump counts as plyometrics." A jump only qualifies as plyometric if it uses a genuine fast stretch-shortening cycle: a brief, imposed eccentric load followed almost instantly by the concentric push. A slow, paused jump squat with a dead stop at the bottom trains a different quality and is not truly plyometric.
• "Plyometrics is only for elite athletes." Low-intensity plyometrics such as pogo hops and jump rope build bone mineral density and rate of force development in general lifters too, and systematic reviews report they can be dosed safely in older adults under supervision, not just in sprinters and jumpers.
• "More jumps always means more power." Research and NSCA guidelines put advanced-athlete session volume at roughly 100 to 140 high-intensity contacts, with returns flattening well before 200; extra volume past that point mainly adds fatigue and injury risk rather than more power.
• "You need a box to do plyometrics." A box or platform is just one tool for one style of plyometric (the depth jump or box jump). Bodyweight bounds, pogo hops, hurdle hops, and medicine ball throws are all plyometric and need no equipment at all.
• "A higher box always builds more power." Past a certain drop height, ground contact time lengthens as the body absorbs more impact, and the movement shifts out of the fast stretch-shortening cycle into a slower, strength-endurance stimulus. Most coaches cap depth jumps around 30 to 45 cm for this reason, going higher only for advanced, well-prepared athletes.

Related terms

Plyometrics FAQ

What is plyometrics in simple terms?

Plyometrics is jump-based training that uses a fast stretch of a muscle right before it contracts, like the quick dip before a jump, to make the following push more powerful. Depth jumps, box jumps, and bounds are common examples used to build explosive power.

What are some examples of plyometric exercises?

Common lower-body examples are box jumps, depth jumps, broad jumps, and bounding; common upper-body examples are plyometric push-ups and medicine ball slams or throws. All of them share the same rapid stretch-then-explode pattern rather than a slow, controlled tempo you would use in a standard strength set.

How often should I do plyometric training?

Most programs use 2 to 3 plyometric sessions a week, spaced with at least 48 hours of recovery between them. General lifters often get results from just 1 to 2 shorter sessions a week focused on quality landings rather than high volume.

Are plyometrics good for weight loss?

Plyometric exercises raise heart rate quickly and can add to a workout's total calorie burn, but they are primarily a power and athleticism tool, not a dedicated fat-loss method. Pair them with resistance training and a calorie deficit for weight loss, not as a stand-alone plan.

Is plyometric training safe for beginners?

Yes, when beginners start with low-intensity drills like pogo hops and box step-downs and master quiet, controlled landings before adding height or speed. Roughly 60 to 80 foot contacts per session is a common starting volume, with intensity increased only after landing mechanics are solid.

What is the difference between plyometrics and ballistic training?

Plyometrics relies on a stretch-shortening cycle, an eccentric load immediately reversed into a concentric push, with ground contact usually under 250 milliseconds. Ballistic training, like a medicine ball throw or jump squat, focuses on continuous concentric acceleration with no landing or reversal constraint.

How many foot contacts should a plyometric session have?

General guidelines put beginners at 60 to 80 contacts, intermediates at 80 to 120, and advanced athletes at roughly 100 to 140 high-intensity contacts per session, two to three sessions a week. Volume climbing well past 140 to 200 tends to add fatigue without adding more benefit.

Can plyometrics help you jump higher?

Yes. Plyometric training directly targets the stretch-shortening cycle and rate of force development that drive a vertical jump, and studies consistently show jump-training programs improve vertical jump height in athletes across sports when volume and intensity are progressed appropriately over several weeks.

Are plyometrics safe for older adults?

Systematic reviews of lower-limb plyometric training in older adults report it can be dosed safely and improve strength, power, and postural control when programs start at low intensity, use bilateral movements, and are supervised, rather than jumping straight to depth jumps or bounding.

What is the stretch-shortening cycle?

The stretch-shortening cycle is the eccentric-then-concentric sequence that underlies every plyometric movement: a muscle lengthens under load, briefly transitions through an amortization phase, then shortens explosively. Efficient use of it, through stored elastic energy and a fast transition, is what makes a rebound more powerful than a dead-stop contraction.

References

1. Plyometric Training. NSCA, Kinetic Select
2. Stretch-Shortening Cycle. NSCA, Kinetic Select
3. Stretch-shortening cycle. Wikipedia
4. The stretch-shortening cycle (SSC) revisited: residual force enhancement contributes to increased performance during fast SSCs of human m. adductor pollicis. Physiol Rep, 2015. PMC4463830
5. Maximizing plyometric training for adolescents: a meta-analysis of ground contact frequency and overall intervention time on jumping ability. Systematic review and meta-analysis. PMC10692103
6. The Efficacy and Safety of Lower-Limb Plyometric Training in Older Adults: A Systematic Review. Sports Med, 2019. PMC6349785
7. Plyometrics: Definition, benefits, and exercises to try. Medical News Today