A 25-year-old man undergoes incremental treadmill testing to exhaustion. Assuming a normal age-related decline in chronotropic capacity, his predicted maximal heart rate is closest to:

• A 160 beats/min
• B 175 beats/min
• C 195 beats/min ✓
• D 220 beats/min

Explanation

Maximal heart rate declines linearly with age and is estimated by the formula HRmax = 220 minus age in years. For a 25-year-old this gives approximately 195 beats/min. This value is largely independent of fitness level; endurance training raises maximal cardiac output mainly by increasing stroke volume, not maximal heart rate. Option D represents the newborn value, and option B would correspond to an age of about 45 years.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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