AIS Chapter 7 Determination of Maximal Oxygen Consumption (VO2max)

Oxygen consumption VO2 = cardiac output (Q) x arteriovenous O2 difference (a-vO2) Cardiac output = heart rate x stroke volume During incremental exercise, VO2 linearly related to power output – VO2max: VO2 not increase despite increasing power output – VO2 plateau or even decrease at intensity higher than VO2max

Oxygen consumption Expression – ml/kg/min, when body weight unsupported, running – L/min when total power output is important, rowing Estimated 30-50% variation in VO2max contributed to genetic factors Physical training can increase VO2max by 5-30% in healthy people Simulate the movement pattern of competition during VO2 tests in athletes

Changes in Cardiac Output 心輸出量 Cardiac output increases due to: – Increased HR – Increased SV (stroke volume, 心搏輸出 ) Plateau at ~40% VO 2max Not enough time for ventricular filling Oxygen uptake by the muscle also increases – Higher arteriovenous difference In endurance athletes, SV keep increasing until VO 2max –  venous return,  EDV,  SV

Changes in Cardiovascular Variables During Exercise