How does ventilation respond to increasing exercise intensity, and what drives the ventilatory threshold?

How does ventilation respond to increasing exercise intensity, and what drives the ventilatory threshold?

• A. Ventilation increases progressively and then more steeply at higher intensities; the ventilatory threshold is driven by accumulations of CO2 and H+ from lactate buffering, prompting disproportionate increases in ventilation.
• B. Ventilation increases only after VO2 max is reached.
• C. Ventilation threshold is defined as the moment when ventilation stops increasing.
• D. Ventilation is independent of lactate buffering.

Answer: (C)

Ventilation rises in two phases as exercise intensifies: a steady increase at lighter intensities, then a steeper rise once a threshold is reached. That ventilatory threshold occurs because lactate begins to accumulate with higher effort, and buffering the resulting H+ with bicarbonate produces CO2. The increasing CO2 stimulates the respiratory centers, causing ventilation to climb disproportionately to the overall metabolic rate. So the best description is that ventilation increases progressively and then more steeply at higher intensities, driven by CO2 produced from lactate buffering. Ventilation does not stop increasing at this point, and it is not independent of lactate buffering.

Ventilation rises in two phases as exercise intensifies: a steady increase at lighter intensities, then a steeper rise once a threshold is reached. That ventilatory threshold occurs because lactate begins to accumulate with higher effort, and buffering the resulting H+ with bicarbonate produces CO2. The increasing CO2 stimulates the respiratory centers, causing ventilation to climb disproportionately to the overall metabolic rate. So the best description is that ventilation increases progressively and then more steeply at higher intensities, driven by CO2 produced from lactate buffering. Ventilation does not stop increasing at this point, and it is not independent of lactate buffering.