Final answer:
Ventilation increases before activity starts due to a variety of factors including a conscious decision to exercise, activation of motor neurons, and stimulation of proprioceptors. These neural factors result in a sudden increase in ventilation as exercise begins.
Step-by-step explanation:
Ventilation increases before activity starts due to a variety of factors. First, a conscious decision to partake in exercise triggers the respiratory centers of the brain to increase ventilation. The respiratory centers may also be stimulated through the activation of motor neurons and proprioceptors in the muscles, joints, and tendons.
These neural factors result in a sudden increase in ventilation as exercise begins. Additionally, the increase in ventilation is supported by the fact that ventilation decreases immediately after exercise ends when these neural stimuli cease.