VO2 max is considered the gold standard measure of cardiorespiratory fitness. The primary limiting factor for VO2 max in sedentary individuals at sea level is:

• A Skeletal muscle mitochondrial oxidative capacity (peripheral limitation)
• B Pulmonary diffusion capacity limiting O2 uptake across the alveolar-capillary membrane
• C Central cardiac output (O2 delivery capacity) — the ability of the heart to pump sufficient oxygenated blood to exercising muscles ✓
• D Blood hemoglobin concentration limiting O2 carrying capacity

Explanation

In healthy sedentary individuals at sea level, VO2 max is primarily limited by central cardiovascular factors — specifically maximal cardiac output (heart rate × stroke volume). Evidence includes: (1) blood transfusion or EPO administration (increasing O2 carrying capacity) increases VO2 max; (2) artificially lowering cardiac output (beta-blockers) reduces VO2 max; (3) elite endurance athletes have VO2 max 2-3x normal primarily due to high maximal cardiac output (up to 40 L/min vs ~20 L/min in untrained). Peripheral mitochondrial capacity becomes limiting after endurance training (when central delivery exceeds peripheral utilization) or in highly trained athletes where central and peripheral limitations are closely matched. Pulmonary diffusion is rarely limiting at sea level in healthy individuals.

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

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Written and medically reviewed by the StethoPrep medical team.