FSHP Academy
Biomechanics & Movement — all lessons

Mechanical Foundations

Basics of biomechanics in sport: kinematics and kineticsLevers, torque and moment armsForce, rate of force development and the stretch-shortening cycle

Movement Analysis

Biomechanics and movement analysisFundamental movement patterns: push, pull, squat, hingeRunning gait analysis

Force, rate of force development and the stretch-shortening cycle

Why producing force quickly can matter more than peak force, the determinants of rate of force development, and how the stretch-shortening cycle boosts jumping, sprinting and throwing.

Advanced Evidence: Strong evidence 3 min read Reviewed 2026-10-31 Status: draft

Learning objectives

  • Define peak force, rate of force development (RFD) and impulse
  • Explain the neural and muscular determinants of early and late RFD
  • Describe the stretch-shortening cycle and its mechanisms
  • Apply RFD and SSC concepts to plyometric and strength programming

Before this lesson

Why this matters

A 200 kg squatter is not automatically a fast sprinter. In sport, the force you can produce in the time available often matters more than the maximum you can eventually reach.

Fundamental concepts

  • Peak force — the highest force achieved (e.g., in an isometric pull).
  • Rate of force development (RFD) — the slope of the force–time curve (ΔF/Δt).
  • Impulse — area under the force–time curve; determines change in velocity.
Force–time curves and rate of force development Two force–time curves reach the same peak force of about 2,800 newtons, but athlete A rises much faster than athlete B. Shaded windows mark typical ground-contact time in maximal sprinting (about 0.1 seconds) and in jumping (roughly 0.2 to 0.3 seconds). Within these short windows athlete A produces far more force, showing why rate of force development can matter more than peak force for fast movements. sprint contact jump take-off same peak force Athlete A — high RFD Athlete B — low RFD force gap at 100 ms 0100200300400500600 0100020003000 Time from onset (ms) · RFD = Δforce ÷ Δtime Force (N)
Figure 1. Two athletes with equal peak force but different RFD. In the short windows available in sprinting and jumping, Athlete A produces far more force. — Original diagram, FSHP Academy (schematic, not to scale).

Time to peak force in maximal isometric contractions is often 300 ms or more, while sprint ground contacts last about 0.1 s and many jumps 0.2–0.3 s.

The science: determinants of RFD

Maffiuletti and colleagues describe RFD as depending on [maffiuletti2016]:

  • Early phase (0–50/75 ms): neural drive — motor unit discharge rates at onset, recruitment speed; also fibre-type characteristics.
  • Later phase (100–200 ms+): increasingly related to maximal strength, muscle size and tendon stiffness.

The stretch-shortening cycle

An eccentric action immediately followed by a concentric action produces more concentric force and power than a concentric action alone. Proposed mechanisms include storage and return of elastic energy in tendons, stretch-reflex potentiation, and more time to build force before the concentric phase [komi2000]. SSC actions are often classified as fast (short contact, e.g., sprinting, pogo hops) or slow (longer contacts, e.g., countermovement jump).

Practical application

Common mistakes and misconceptions

Assessment and practical tools

Force plates provide jump height, peak force, RFD and reactive strength index (jump height ÷ contact time). Compare an athlete with themselves over time using the same protocol — see force plates.

Case study

A rugby forward squats 2× body weight but has a modest countermovement jump. Force-plate data show slow force rise. The coach keeps strength work but adds jump squats, med-ball throws and low-volume plyometrics; over 8 weeks RFD and jump height improve.

Further learning: video lessons

Video links are only marked “verified” after a human has watched them. Unverified entries open a YouTube search for that channel and topic rather than a guessed link.

Introductory needs verification — opens a YouTube search

Rate of force development explained

Science for Sport

You will understand: why speed of force matters

Why: Coaching-oriented explanation.
Technical needs verification — opens a YouTube search

Stretch-shortening cycle and plyometrics

NSCA

You will understand: mechanisms and programming of plyometrics

Why: Professional organisation content.

Knowledge check

Knowledge check · 0/5

1. Rate of force development is…

Answer B. RFD = ΔF/Δt, usually over defined windows (e.g., 0–50, 0–200 ms).

2. Early-phase RFD (0–50 ms) is most influenced by…

Answer B. Maffiuletti et al. highlight neural factors early and maximal strength later.

3. A countermovement jump is usually higher than a squat jump because of…

Answer A. The preceding eccentric phase enhances concentric performance.

4. Which is NOT a proposed SSC mechanism?

Answer D. Fibre number does not change acutely.

5. A meta-analysis of plyometric training found…

Answer B. Markovic (2007) reported meaningful improvements in jump height.

Short-answer & application questions

  1. Explain why a very strong but slow athlete may struggle in sprinting.
  2. Describe a progression from low- to high-intensity plyometrics.
  3. Interpret the difference between two athletes’ force–time curves with equal peak force.

Key takeaways

  • Many sport actions last 0.1–0.3 s, less than the time needed to reach peak force; RFD determines force available in that window.
  • Early RFD (first ~50 ms) depends largely on neural drive; later RFD relates more to maximal strength.
  • The SSC (eccentric quickly followed by concentric) increases concentric output through elastic energy and neural mechanisms.
  • Plyometric training improves jump performance; heavy strength training also raises late RFD.

Connected topics

physiology

Neuromuscular adaptations to training

strength conditioning

Plyometrics and explosive power training

sports technology

Force plates (e.g. VALD ForceDecks)

physiology

Motor units, recruitment and rate coding

References

  1. Maffiuletti NA, Aagaard P, Blazevich AJ, et al. (2016). Rate of force development: physiological and methodological considerations. European Journal of Applied Physiology, 116(6):1091–1116. doi:10.1007/s00421-016-3346-6 Narrative review check pending
  2. Komi PV (2000). Stretch-shortening cycle: a powerful model to study normal and fatigued muscle. Journal of Biomechanics, 33(10):1197–1206. Narrative review check pending
  3. Markovic G (2007). Does plyometric training improve vertical jump height? A meta-analytical review. British Journal of Sports Medicine, 41(6):349–355. Meta-analysis check pending

Educational content only — not medical advice. Consult a qualified clinician for diagnosis or treatment.