Kinesiology
Movement language
Kinesiology questions test whether you can describe movement precisely. Learn the planes and their movements: sagittal (flexion/extension), frontal (abduction/adduction, lateral flexion), transverse (rotation, pronation/supination). Osteokinematics is bone movement at a joint; arthrokinematics is the roll, glide, and spin of joint surfaces.
Muscle roles and actions
Every muscle has an origin (usually more proximal, more fixed) and an insertion (usually more distal, more mobile). Actions are concentric (shortening, accelerating), eccentric (lengthening under tension, decelerating and producing the most soreness), and isometric (no length change). Roles include agonist (prime mover), antagonist, synergist (assists), and fixator (stabilizes origin).
Levers and length-tension
- First class: fulcrum between effort and load (nodding the head).
- Second class: load between fulcrum and effort (calf raise).
- Third class: effort between fulcrum and load - the most common in the body (biceps curl).
A muscle generates the most force at its resting-to-mid length; too short (active insufficiency) or too long (passive insufficiency) reduces output. Reciprocal inhibition describes the antagonist relaxing as the agonist contracts; the stretch reflex resists rapid lengthening.
Traps
Students reverse the concave-convex rule and mislabel second- versus third-class levers. Also, "origin" and "insertion" can reverse during a reversal of muscle action - the bellies do not change, only which end moves.
Rule of thumb
Convex moving on concave: roll and glide are opposite. Concave moving on convex: roll and glide are the same direction.