Training glossary
Plain-English definitions of the terms used across the BounceLab articles, exercises and assessment. Search the full list or jump to a letter.
48 terms
A
Amortization Phase
The brief isometric transition between the eccentric and concentric phases of the SSC. Shorter amortization means more elastic energy is reused.
ACTN3
A gene associated with fast-twitch muscle function; the RR genotype correlates with power performance. It sets part of the ceiling but explains little of your next two years of training.
ATP-CP
The phosphocreatine energy system that powers maximal efforts for seconds — restored in 2–5 minutes, which is why power sets need long rest.
B
Box Jump
A slow-SSC plyometric where the athlete jumps onto an elevated box. It builds force absorption and redirection with lower impact than depth jumps.
Beta-Alanine
A supplement (3–5 g/day) that buffers intramuscular acidosis, helping repeated high-intensity efforts of 60–240 seconds.
C
CMJ
Countermovement jump: a vertical jump performed from a standing dip into an immediate takeoff. It recruits the stretch-shortening cycle and is the standard anchor test for jump monitoring. A true CMJ is performed hands on hips with no arm swing; a jump with an arm swing is a separate test.
Concentric Contraction
Muscle shortening under load — the push-off phase of jumping. Concentric strength is what the squat jump isolates.
Contact
The volume unit for plyometrics: one foot or both feet landing once. Weekly contacts are banded by level (60–100 beginner, 100–150 intermediate, 120–200 advanced).
Creatine
A well-evidenced supplement (5 g/day monohydrate) that improves power, sprint and jump performance by supporting rapid ATP resynthesis.
D
DOMS
Delayed-onset muscle soreness: muscle pain peaking 24–72 hours after eccentric work. It is a normal training response, not an injury.
Depth Jump
A high-intensity plyometric where the athlete steps off a box, lands and immediately rebounds as high as possible. Quality is scored by contact time under 0.25 seconds and rebound height.
E
EUR
Eccentric Utilization Ratio: the ratio of countermovement jump (CMJ) height to squat jump (SJ) height (EUR = CMJ ÷ SJ). It quantifies the stretch-shortening cycle (SSC) elastic contribution. An optimal ratio typically sits between 1.10 and 1.15; values below 1.05 point to an elasticity deficit, while values above 1.20 indicate a maximum strength deficit.
Eccentric Contraction
Muscle lengthening under load — the landing and lowering phases of jumping. Eccentric work builds force absorption and triggers most DOMS.
F
F-V Profile
Force-velocity profile: a test that fits jump performance at different loads to estimate max force (F₀), max velocity (V₀), their balance (Sfv) and peak power (Pmax). It separates force deficits from velocity deficits.
G
Ground Contact Time
The time each foot spends on the ground during a jump, hop or sprint step. Short contact times (often under 250ms in fast plyometrics) preserve elastic energy and are a key RSI component.
H
I
K
M
MTSS
Medial tibial stress syndrome (shin splints): an overload response of the tibial periosteum, common when jump or run volume rises too fast.
Mesocycle
A training phase lasting several weeks with one goal — tolerance, strength, conversion or peaking. A macrocycle is made of mesocycles.
Macrocycle
The full training plan, typically 12–16 weeks, ending with a peak and test phase.
N
P
Pmax
Peak power output, estimated as F₀ × V₀ / 4 in the force-velocity profile. It represents the overall power ceiling.
Plyometrics
Exercises that use the stretch-shortening cycle — eccentric loading followed by an immediate concentric explosion — to train power and reactivity.
Periodization
Structuring training into phases so the stimulus keeps changing and performance peaks when it matters — typically base → strength → power → peak.
R
RSI
Reactive Strength Index: jump height divided by ground contact time, typically measured in depth jumps. It quantifies how quickly an athlete converts a stretch into a rebound.
Readiness Score
BounceLab's weighted 0–100 summary of your jump profile. It combines max strength, power/speed, mobility, glute function, injury history, recovery, technique and training history after renormalizing over the dimensions actually collected.
RFD
Rate of force development: how quickly force rises at the start of a contraction. RFD is a primary determinant of explosive movements like jumping.
Relative Strength
Strength expressed per kilogram of bodyweight (e.g., squat 1RM ÷ bodyweight). Above 1.8x is excellent jump potential; below 1.2x, strength or fat loss should come first.
S
Standing Broad Jump
A two-foot horizontal jump from a standing start, used to test horizontal power. Sometimes called the standing long jump; BounceLab uses 'broad jump' to avoid confusion with the runway long-jump event.
SJ
Squat jump: a vertical jump from a static half-squat position with no countermovement. It isolates pure concentric strength and is compared with CMJ to estimate SSC utilization.
SSC
Stretch-shortening cycle: the eccentric stretch, brief amortization and immediate concentric shortening of a muscle. It is the mechanism plyometrics train and the source of the elastic contribution to jumping.
Strength Deficit
A force-velocity imbalance where an athlete expresses jump power well but lacks the maximum-strength reserve behind it. The usual prescription is to prioritize squat and deadlift strength while keeping plyometric volume low.
Supercompensation
The rebound above baseline that follows a well-timed reduction in training load — the reason PRs appear the week after a deload.
V
Velocity Deficit
A force-velocity imbalance where an athlete is strong but cannot express that force quickly enough during a jump. The usual prescription is rate-of-force-development and plyometric work rather than more heavy lifting.