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CSCS Anatomy & biomechanics: key points

This topic covers how muscles contract, motor unit recruitment, levers and planes of motion, and basic mechanics formulas. Many questions test definitions directly, so precise vocabulary pays off.

Points that often appear

What changes length in the sliding filament theory

During contraction the A-band (the length of myosin) stays the same while the I-band and H-zone shorten, as actin slides between the myosin filaments.

Calcium binds to troponin

Calcium released from the sarcoplasmic reticulum binds to troponin, shifting tropomyosin and exposing binding sites on actin so myosin can attach.

The size principle

Small, low-threshold motor units are recruited first, and larger, high-threshold units are added as force demands increase.

Most body levers are third-class

In a third-class lever the effort lies between the fulcrum and the load. Elbow flexion is a classic example, and it is the most common lever type in the body.

Planes of motion

The sagittal plane covers flexion and extension (e.g., squats), the frontal plane abduction and adduction (lateral raises, side lunges), and the transverse plane rotation.

Proprioceptors

Muscle spindles detect muscle length and its rate of change and trigger the stretch reflex. Golgi tendon organs detect tension and tend to inhibit muscle activity.

Quick reference

Quantity	Formula
Power	Force × velocity (work ÷ time)
Work	Force × distance
Force	Mass × acceleration
Impulse	Force × time

Watch for this trap

All four mechanics formulas often appear together as answer choices. Learn the whole table at once and any version of the question becomes straightforward.