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 cycleMovement Analysis
Biomechanics and movement analysisFundamental movement patterns: push, pull, squat, hingeRunning gait analysisBiomechanics and movement analysis
How to analyse human movement systematically — qualitative observation, 2D video, 3D capture, sensors and force measurement — and how to avoid over-interpreting what you see.
Learning objectives
- Use a structured qualitative analysis model (prepare, observe, evaluate, intervene)
- Set up valid 2D video analysis
- Compare 2D video, 3D motion capture, wearable sensors and force plates
- Recognise reliability limits and the weak predictive value of single movement observations for injury
Before this lesson
Why this matters
Coaches and trainers analyse movement constantly, usually by eye. Doing it systematically — and knowing the limits of what you see — makes feedback more useful and avoids alarming clients over normal variation.
Fundamental concepts: a qualitative analysis model
Knudson describes a four-task approach [knudson2007]:
- Prepare — know the goal of the movement and its critical features (e.g., hip–knee coordination in a squat).
- Observe — choose vantage points, number of trials, and use video where possible.
- Evaluate and diagnose — compare against critical features; prioritise the issue most limiting performance or safety.
- Intervene — give one focused cue, modify the task or load, then re-observe.
Measurement tools
| Tool | Strengths | Limitations |
|---|---|---|
| Eye / 2D video (smartphone) | Cheap, quick, good for feedback | Plane-specific, parallax, low frame rate blur |
| 3D marker-based capture | Reference for kinematics | Expensive, lab-based, soft-tissue artefact |
| Markerless 3D / AI pose | Convenient, emerging | Accuracy varies by system and task |
| Inertial sensors (IMUs) | Field use, continuous | Drift, placement sensitivity |
| Force plates | Kinetics: GRF, RFD, impulse | Cost, mostly vertical-jump/landing tasks |
Setting up 2D video
- Camera perpendicular to the plane of interest (side-on for sagittal, front-on for frontal).
- At the height of the joint of interest, far enough away with zoom to reduce perspective error.
- Use ≥60 fps (≥120–240 for sprinting or jumping) and a fast shutter to avoid blur.
- Keep setup identical between sessions.
The prediction problem
Movement observations can be reliable and useful for coaching, but their ability to predict individual injury is poor. Bahr explains that even genuine risk factors rarely separate future injured from uninjured individuals accurately [bahr2016]; a large prospective study found the drop vertical jump could not usefully identify players who later sustained ACL injuries [krosshaug2016].
Practical application
Common mistakes and misconceptions
Case study
A runner wants a gait analysis. The coach films side and rear views on a treadmill at 120 fps, notes overstriding at easy pace, and cues a slightly higher step rate. Re-filming confirms the change; running comfort improves — without claiming that the original pattern “caused” a past injury.
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.
Video analysis for coaches — setup and pitfalls
sports biomechanics educators (search)
You will understand: practical camera setup for valid 2D analysis
Why: Verify a specific video before publishing.
Qualitative movement analysis model
university kinesiology lectures (search)
You will understand: a structured approach to observing skill
Why: Supports a systematic method.
Knowledge check
Knowledge check · 0/5
1. For 2D video analysis of knee flexion in a squat, the camera should be…
2. Parallax error in 2D video occurs when…
3. Which is generally the reference (“gold standard”) for joint kinematics?
4. Bahr (2016) argued that screening tests rarely predict injury because…
5. The first step of a qualitative analysis model is to…
Short-answer & application questions
- Describe your camera setup for analysing a single-leg squat in two planes.
- List three sources of error in smartphone video analysis and how to reduce them.
- Explain how you would use movement analysis with a client without implying they are “broken”.
Key takeaways
- Qualitative analysis works best with a clear model — prepare, observe, evaluate/diagnose, intervene.
- 2D video needs a camera perpendicular to the plane of motion, adequate frame rate and consistent setup.
- 3D capture and force plates are more accurate but costly; wearables trade accuracy for convenience.
- Single movement observations predict individual injury poorly; use analysis to coach and track change.
Connected topics
Postural and functional assessment (Prehab assessment tool)
assessmentLimits of movement screens and postural assessment
sports technologyMotion analysis tools: cameras, sensors and apps
sports technologyRunning gait analysis (e.g. GaitON)
prehab rehabPrinciples of injury prevention and recovery
This is the canonical lesson for: Prehab & Rehabilitation → Foundations of MSK Rehabilitation
References
- Knudson D (2007). Fundamentals of Biomechanics (2nd ed.). Springer. Textbook check pending
- Bahr R (2016). Why screening tests to predict injury do not work—and probably never will…: a critical review. British Journal of Sports Medicine, 50(13):776–780. doi:10.1136/bjsports-2016-096256 Narrative review check pending
- Krosshaug T, Steffen K, Kristianslund E, et al. (2016). The vertical drop jump is a poor screening test for ACL injuries in female elite soccer and handball players. American Journal of Sports Medicine, 44(4):874–883. doi:10.1177/0363546515625048 Cohort check pending
Educational content only — not medical advice. Consult a qualified clinician for diagnosis or treatment.