Increased ventilation at sta of exercise is due to?

Ans. is 'b' i.e., Proprioceptors[Ref Ganong 23'd/e p. 636)In moderate exercise the abrupt increase in ventilation at the sta of exercise is due to psychic stimuli and afferent impulsE from proprioceptors in muscles, tendons and joints.Aerial pH, PCO2, and PO2, remain constant during moderate exercise because increase in ventilation is propoionate to increase in O, consumption.