Physiological Changes Associated with Aging
What the exam tests
This domain tests whether you can separate normal aging, disuse, and pathology, then adjust training variables accordingly. Expect questions on sarcopenia, bone density, cardiovascular capacity, thermoregulation, and sensory decline.
Core changes to know
- Sarcopenia: muscle mass falls roughly 3–8% per decade after age 30 and faster after 60; type II fibers and motor units are lost disproportionately, so power declines more than raw strength.
- Bone: peak bone mass occurs near age 30; women lose rapidly for 5–10 years after menopause. Weight-bearing and resistance loading are the main countermeasures.
- Cardiovascular: VO2max falls about 10% per decade in sedentary adults; maximal heart rate drops roughly 1 beat per year; arteries stiffen, raising systolic pressure.
- Neuromuscular and sensory: nerve conduction and reaction time slow; vestibular, proprioceptive, and visual input degrade, so balance corrections are slower and rely more on vision.
- Other: lower resting metabolic rate, reduced thirst and renal concentrating ability (dehydration risk), thinner skin, poorer thermoregulation, and altered drug clearance.
Worked example
A 72-year-old woman needs a moderate-intensity heart-rate estimate. The 220 − age formula gives 148 bpm. The Tanaka equation, 208 − (0.7 × 72), gives 158 bpm. Reasoning: 220 − age systematically underestimates maximal heart rate in older adults, so 148 would under-prescribe intensity. Use the Tanaka value as a starting ceiling and confirm with RPE 12–13 on the 6–20 Borg scale, because beta-blockers or a pacemaker can make heart rate unreliable.
Traps that cost marks
- Treating every decline as inevitable instead of separating disuse and disease.
- Confusing sarcopenia with cachexia or frailty.
- Ignoring medications that blunt heart rate or cause orthostatic hypotension.
- Programming from heart rate alone without perceived exertion or symptom checks.