Unit 1: The Human Body in Motion
What you must understand
Unit 1 links the skeletal, muscular, respiratory and circulatory systems to how the body produces and delivers energy for movement. Candidates must know the major bones and joints (ball-and-socket, hinge, pivot, gliding), the types of muscle contraction (isometric, concentric, eccentric), and the agonist–antagonist–stabiliser roles. You must also explain how the cardiorespiratory system supplies oxygen and removes wastes, and describe the three energy systems: ATP–PC (immediate, ~10 seconds), anaerobic glycolysis (short-term, up to ~2 minutes) and aerobic (long-term). Know the fuels each system uses and the by-products produced.
Traps to watch
A common trap is confusing the energy systems' duration and intensity: ATP–PC is high-intensity but very brief, not the system for a 400 m race. Another trap is mixing up eccentric (muscle lengthening under tension) with concentric (shortening). Students also confuse the agonist (prime mover) with the antagonist (opposing muscle). Do not state that aerobic metabolism produces lactic acid; lactate accumulation is associated with anaerobic glycolysis.
Rule of thumb and worked example
Use the intensity–duration rule: the higher the intensity and shorter the effort, the more the ATP–PC system dominates. For a 100 m sprint, ATP–PC is dominant, with anaerobic glycolysis contributing later. For a 10 km run, aerobic dominates. Always match the system to the effort's intensity and duration, then justify with fuel and by-product.
Exam skill
Define terms precisely and link structure to function. When asked to 'explain', give a cause-and-effect chain rather than a list.