Which of the following is NOT a factor that contributes to increased ventilation during exercise?

The correct choice indicates that decreased pH levels do not contribute to increased ventilation during exercise, and this is based on the body’s physiological responses during physical activity. During exercise, the body generates more carbon dioxide, which leads to an increase in hydrogen ions and a corresponding decrease in pH (making the blood more acidic). This drop in pH is a significant stimulus for ventilation.

However, the body typically responds to high carbon dioxide levels and the resultant low pH by increasing respiratory rate and depth to expel the excess carbon dioxide, thus bringing pH back to normal. Rather than being a contributing factor to the initial increase in ventilation, decreased pH is more of an effect of exercise-induced hypercapnia (increased carbon dioxide levels), which subsequently triggers ventilation.

In contrast, motor impulses from the cerebral cortex are crucial for initiating exercise and enhancing ventilation by overriding the normal chemoreceptor responses. Increased body temperature, which occurs during exercise, stimulates the respiratory control centers to facilitate increased oxygen intake. Similarly, elevated catecholamine levels, often resulting from the ‘fight or flight’ response during exercise, serve to further stimulate ventilation rates. Thus, they all contribute positively to the increase in ventilation during exercise, unlike decreased pH, which is more