The VO2max (maximal oxygen uptake) is the gold standard of aerobic fitness. The primary limiting factor for VO2max in healthy, trained individuals at sea level is:

• A Pulmonary diffusing capacity (DLCO)
• B Maximal cardiac output (heart rate × stroke volume) — central oxygen delivery ✓
• C Peripheral skeletal muscle oxidative enzyme capacity
• D Haemoglobin concentration in arterial blood

Explanation

In healthy individuals at sea level, VO2max is primarily limited by central oxygen delivery — specifically, the maximal cardiac output achievable (Fick principle: VO2max = CO × [CaO2 − CvO2]). The lungs can fully saturate haemoglobin even at maximum exercise in healthy subjects. Training-induced increases in VO2max primarily result from increased stroke volume (eccentric cardiac hypertrophy). Peripheral factors (mitochondrial density, capillary density) become limiting in untrained states or with very high-intensity interval training. DLCO limits VO2max only at altitude or in athletes with exercise-induced hypoxaemia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.