Question

The maximum possible metabolic rate during exercise is

A. Reached when the blood lactate level starts to fall. 

B. Reached when the respiratory exchange ratio starts to fall. 

C. Reached when ventilation reaches the maximum breathing capacity. 

D. Reduced by about half if the hemoglobin level falls by half. 

E. About 50 times the resting rate in an athlete.

Answer 1

A. False The lactate level keeps rising with increasing severity of exercise. 

B. False Increasing lactate acid increases ventilatory elimination of CO₂; a rising respiratory exchange ratio suggests that exercise is approaching maximal. 

C. False The level of ventilation in exercise does not reach the maximum breathing capacity. 

D. True Oxygen delivery depends crucially on the hemoglobin level. 

E. False The limit is about half of this.