Plyometrics
Also known as: Plyometric Training, Jump Training, Stretch-Shortening Cycle Training, SSC Work
Explosive-movement training that exploits the stretch-shortening cycle — the rapid transition from an eccentric loading phase to a concentric powerful action — to develop rate of force development, elastic-energy reuse, and reactive strength. The canonical examples are depth jumps, box jumps, bounds, and medicine-ball throws; the mechanism is a short, sharp eccentric that pre-loads the muscle-tendon unit followed by an immediate concentric contraction that releases stored elastic energy plus the reflexive muscular contribution. Plyometrics sit between pure strength work (long time under tension, high force, low velocity) and pure speed work (low load, high velocity, no explicit stretch pre-load), addressing the reactive-power gap that neither pure end covers.
Formula
There is no calculation — plyometrics are prescribed by intensity level, contact count, and rest interval:
Intensity levels (Chu classification, low → high):
- Low: skipping, in-place hops, medicine-ball chest passes
- Moderate: box jumps (30-50 cm), tuck jumps, bounds
- High: depth jumps from 30-60 cm, single-leg bounds, hurdle hops at height
- Shock: depth jumps from 60-120 cm (Verkhoshansky's original method)
Volume: measured in ground contacts per session, not sets × reps.
- Beginner: 40-80 contacts / session
- Intermediate: 80-140 contacts
- Advanced: 140-220 contacts
- Elite athletes rarely exceed 220 contacts per session; volume beyond that trades power for accumulated fatigue.
Rest: 1:5 to 1:10 work-to-rest ratio between sets — plyometrics train the nervous system's rate coding, and incomplete rest degrades the quality of every subsequent contact.
Frequency: 2-3 sessions per week maximum for high-intensity work; low-intensity work can sit alongside daily.Example
Basketball player in a pre-season conditioning block: 8 sets of 5 box jumps from a 40 cm box, landing on a 50 cm target (moderate intensity, 40 contacts) + 6 sets of 4 depth jumps from a 50 cm box into a max-effort vertical (high intensity, 24 contacts) = 64 total contacts in the session. Rest ~2 minutes between sets — enough to allow every jump to be maximal-intent. Same session repeated twice per week for 6 weeks typically produces measurable jump-height gains (2-6 cm) that persist across the season if the stimulus is maintained at reduced volume. The same box-jump-only session without the depth-jump component teaches jumping but does not develop the reactive-strength component that transfers to game-time rebounding.
How Afitpilot Uses This
Afitpilot's plan generator does not currently prescribe plyometric-specific work. Athletes whose sport or goal requires reactive power (basketball, volleyball, sprinting, athletics-throw events, martial arts) should treat plyometrics as a distinct training modality that lives alongside strength work, not inside it — same rules as accommodating resistance: log it as a variant, not a substitute. Practical translation: (1) plyometric quality degrades fast under fatigue, so plyometric work belongs early in the session, not after a heavy squat session; (2) contact count is the honest volume unit, not set count — a session logging '3×5 depth jumps' is really a 15-contact session; (3) plyometric progression is slower than strength progression — 6-week blocks with 2-3 sessions/week typically produce the outcomes the research reports; (4) advanced 'shock' plyometrics (>60 cm drop heights) require substantial prior strength base and joint tolerance, and produce disproportionate CNS-fatigue cost that has to be programmed around.
Plyometrics in practice
| Who / Context | Value | Note |
|---|---|---|
| Peak ground reaction force — depth jump from 50 cm | 5-8× bodyweight | One of the highest per-contact loads in athletic training |
| Ground contact time — elite reactive athlete | 150-200 ms | Below this range, most of the elastic-energy return goes unused |
| Ground contact time — recreational athlete | 250-400 ms | The reactive-strength gap between recreational and elite jumping |
| Typical vertical-jump gain over a 6-week block | 2-6 cm | Population average for intermediate athletes; advanced athletes gain less per block |
| Contact count for a beginner session | 40-80 total | Volume beyond this range degrades quality before it improves adaptation |
| Contact count for an advanced session | 140-220 total | Ceiling before diminishing returns and injury risk climb |
| Rest-to-work ratio for high-intensity plyos | 1:5 to 1:10 | Incomplete rest degrades every subsequent contact — quality over volume |
| Sport with strongest plyometric transfer | Volleyball, basketball, track sprints/jumps | Sports where reactive strength is the competition-day performance ceiling |
Known Limitations
- •Plyometric quality is the whole point, and quality degrades with fatigue faster than perceived effort suggests. A depth jump on rep 8 of a set of 10 is a substantially worse depth jump than rep 1 — not because the muscles have failed but because ground-contact time has crept up and reactive strength has dropped. Long plyometric sets are almost always mistakes.
- •Landing surface, footwear, and ground stiffness meaningfully change the stimulus. A depth jump from 40 cm onto a rubber floor is a different exercise from the same jump onto concrete or grass. Standardise the surface across a block or the progression signal gets muddled.
- •The joint-loading cost of plyometrics is high. Peak ground reaction forces in depth jumps can reach 5-10× bodyweight — an amount healthy joints tolerate well but injured, arthritic, or novice-athlete joints do not. Plyometric prescription for older adults or return-to-sport athletes has to grade intensity carefully.
- •The evidence for plyometrics transferring to sport performance is strongest for jump-specific, sprint-specific, and change-of-direction outcomes (Markovic 2007 meta-analysis; Sáez de Villarreal 2010 on jump performance), and weakest for absolute strength (where standard resistance training is more direct) and endurance (where the reactive-strength stimulus doesn't align with the goal). Adding plyometrics to a marathon block is usually a mistake.
- •Depth-jump prescriptions in particular have been over-generalised from Verkhoshansky's original work on elite Soviet track and field athletes. His 'shock method' (drops from 110 cm) targeted athletes with an extensive prior training base; applying it to intermediate lifters or general-population trainees routinely produces knee, ankle, or lower-back complaints without the compensating performance gain.
- •Contact count and jump height are not equivalent progress metrics. Volume can be increased (more contacts) without any change in reactive-strength quality; height gains matter more than count gains once the session's contact count is in a productive range.
Science Context
The formal study of the stretch-shortening cycle began with Cavagna and colleagues in the 1960s and was translated into Soviet athletic practice by Yuri Verkhoshansky, who codified the depth-jump 'shock method' in the 1960s-70s. Chu (1998, 'Jumping into Plyometrics') brought the modern intensity classification into Western coaching. The evidence base for plyometric training on jump performance is well-replicated: Markovic 2007 meta-analysis found average 8-10% jump-height improvement across ~40 studies, with larger effects for combined resistance-and-plyometric protocols than either alone. Sáez de Villarreal et al. 2010 confirmed transfer to sprint performance in trained athletes. The transfer to absolute strength is weaker (standard resistance training outperforms plyometrics for 1RM gains); the transfer to endurance is negligible-to-negative. The mechanism split between elastic-energy return, stretch-reflex contribution, and neural rate-of-force-development is well-characterised in the literature (Komi 2000 review), though the relative proportions vary by exercise, athlete, and drop height. Afitpilot's practical position for self-coached athletes: plyometrics are a legitimate specialised tool for sports that reward reactive power, best scheduled early in the session when quality is highest, and best programmed by contact count rather than by set count. For lifters, hybrid athletes, and endurance-focused populations, dedicated plyometric blocks are usually optional and often skipped without meaningful cost.