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

Basics of biomechanics in sport: kinematics and kinetics

The core vocabulary and laws of biomechanics — displacement, velocity, acceleration, force, Newton’s laws, impulse–momentum and ground reaction forces — applied to exercise and sport.

Beginner Evidence: Established consensus 3 min read Reviewed 2026-10-31 Status: draft

Learning objectives

  • Distinguish kinematics from kinetics and linear from angular motion
  • Apply Newton’s three laws to human movement
  • Use the impulse–momentum relationship to explain jumping, sprinting and landing
  • Interpret ground reaction forces and centre of mass in practice

Before this lesson

Why this matters

Biomechanics turns “that looks good” into measurable cause and effect. It explains why some techniques produce more force, why landings hurt, and how to read data from force plates and video.

Fundamental concepts

BranchDescribesVariables
KinematicsMotion itselfPosition, displacement, velocity, acceleration, joint angles
KineticsCauses of motionForce, torque, impulse, momentum, power

Motion can be linear (translation) or angular (rotation about an axis); most human movement is angular motion at joints producing linear motion of the body [knudson2007].

Newton’s laws applied

  1. Inertia — a body stays at rest or in uniform motion unless a net force acts. Changing direction in sport requires force.
  2. F = m·a — acceleration is proportional to net force and inversely to mass. Faster acceleration needs more net horizontal force relative to body mass.
  3. Action–reaction — every force has an equal and opposite reaction. A sprinter pushes back and down; the ground reaction force (GRF) pushes the athlete forward and up.

Impulse–momentum

Net force × time (impulse) = change in momentum = m × ΔvImpulse in N·s; momentum = mass × velocity (kg·m·s⁻¹).
  • Jumping: take-off velocity depends on net vertical impulse. More force, or force applied over a longer effective time (as in a countermovement), increases it.
  • Landing: momentum must be reduced to zero. Flexing hips, knees and ankles lengthens the time, lowering peak force.
  • Sprinting: ground contact is very short (~0.1 s at top speed), so the ability to produce force quickly matters — see force and RFD.

Ground reaction forces and centre of mass

Vertical GRF in running commonly peaks at around 2–3 times body weight; landings from jumps can be considerably higher [winter2009]. The centre of mass (COM) — the balance point of the body — lies roughly in front of the upper sacrum when standing and moves with posture. Stability improves with a larger base of support and a lower COM.

Practical application

Common mistakes and misconceptions

Case study

A volleyball coach uses a jump mat and video: a player jumps higher with an arm swing than without. Using impulse–momentum, the coach explains that the arm swing increases vertical force during propulsion, and builds arm-swing timing into jump training.

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

Newton’s laws of motion

Khan Academy

You will understand: the three laws with worked examples

Why: Solid physics foundation.
Technical needs verification — opens a YouTube search

Ground reaction forces in running and jumping

university sports biomechanics channels (search)

You will understand: interpreting force–time data

Why: Verify a specific lecture before publishing.

Knowledge check

Knowledge check · 0/5

1. Which is a kinetic variable?

Answer C. Kinetics deals with forces; the others describe motion (kinematics).

2. Impulse equals…

Answer B. Impulse (N·s) = average net force × time and equals the change in momentum.

3. Landing with bent knees reduces peak force mainly because it…

Answer B. The same impulse spread over longer time means lower peak force.

4. A sprinter accelerates forward because the ground pushes…

Answer B. Newton’s third law — the ground reaction force is equal and opposite to the force applied.

5. The centre of mass of a standing adult is roughly…

Answer B. Approximately at the level of the second sacral vertebra in anatomical position; it moves with posture.

Short-answer & application questions

  1. Use impulse–momentum to explain why a countermovement increases jump height.
  2. Explain why a wider base of support increases stability.
  3. Describe the forces acting on a runner at mid-stance.

Key takeaways

  • Kinematics describes motion (position, velocity, acceleration); kinetics explains its causes (forces, torques).
  • Newton’s laws — inertia, F = ma, action–reaction — underpin every movement analysis.
  • Impulse (force × time) equals change in momentum; to jump higher or sprint faster, apply more net force in the available time.
  • Ground reaction forces in running and landing are multiples of body weight; landing technique changes how quickly they rise.

Connected topics

biomechanics

Levers, torque and moment arms

biomechanics

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

biomechanics

Biomechanics and movement analysis

sports technology

Force plates (e.g. VALD ForceDecks)

This is the canonical lesson for: Sports Technology → Module 2 – Biomechanics & Motion Capture

References

  1. Knudson D (2007). Fundamentals of Biomechanics (2nd ed.). Springer. Textbook check pending
  2. Winter DA (2009). Biomechanics and Motor Control of Human Movement (4th ed.). Wiley. Textbook check pending

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