Anatomy and Physiology of Human Movement
Domain 1: Anatomy and Physiology of Human Movement
The exam tests how structure produces movement: muscle contraction, joint mechanics, lever systems, and neural control. Expect applied questions that ask you to identify a muscle’s role or explain why a joint action is weak at a particular angle.
Core rules
- Muscle hierarchy: sarcomere → myofibril → muscle fiber → fascicle. In sliding-filament theory, Ca2+ binds troponin, tropomyosin moves, myosin heads form cross-bridges, and ATP detaches them.
- Fiber types: type I is slow, fatigue-resistant and oxidative; type IIa is fast and moderately oxidative; type IIx is fastest and most glycolytic. The size principle recruits small motor units before large ones.
- Muscle roles: agonist produces the action, antagonist opposes it, synergist assists, stabilizer fixes a joint. Origin is usually proximal; insertion is distal and more mobile.
- Joint motion: osteokinematics describes bone movement in a plane about an axis; arthrokinematics describes roll, glide, and spin at the joint surface. Most limb levers are third-class and favor speed/range over force.
- Sensors: muscle spindles detect stretch and rate of stretch; Golgi tendon organs detect tension. Reciprocal inhibition reduces antagonist activity during agonist contraction.
Worked example
In a dumbbell biceps curl, elbow flexion occurs in the sagittal plane about a frontal axis. The biceps brachii is an agonist, the triceps is the antagonist, the brachioradialis assists, and the rotator cuff stabilizes the shoulder. The elbow is a third-class lever: effort (biceps) lies between axis (elbow) and load (hand). That arrangement increases hand speed but requires a relatively large muscle force.
Traps
Do not swap origin and insertion, or plane and axis. Antagonists do not always “switch off”; co-contraction can stabilize. The muscle spindle is not a tension sensor. Also, a muscle can act at more than one joint, so its role changes with position.