The interactions between locomotion and respiration.

Respiration is a vital motor activity requiring fine-tuning to adjust to metabolic changes. For instance, respiration increases in association with exercise. In this chapter, we review the mechanisms underlying respiratory changes during exercise. Three specific hypotheses were proposed. First, the chemoreception hypothesis suggests that chemoreceptors located centrally or peripherally modify breathing by detecting metabolic changes in arterial blood or cerebrospinal fluid. Second, the central command hypothesis stipulates that central neural connections from brain motor areas activate the respiratory centers during exercise. Third, the neural feedback hypothesis stipulates that sensory inputs from the contracting limb muscles modulate the respiratory centers during exercise. We present evidence from the literature supporting possible contributions from these three mechanisms. This review also addresses future research challenges relative to respiratory modulation during exercise.