Running and Breathing in Mammals

TLDR

Locomotion and breathing are mechanically coupled in mammals, with phase‑locked limb and respiratory cycles observed in species such as jackrabbits, dogs, horses, humans, and even flying birds, typically at a 1:1 stride‑to‑breath ratio in quadrupeds. Human runners employ several phase‑locked breathing patterns, most commonly a 2:1 stride‑to‑breath ratio, and despite reduced mechanical constraints from bipedal gait, the need for locomotor‑respiratory synchronization persists, suggesting it is essential for sustained aerobic exercise in endothermic vertebrates.

Abstract

Mechanical constraints appear to require that locomotion and breathing be synchronized in running mammals. Phase locking of limb and respiratory frequency has now been recorded during treadmill running in jackrabbits and during locomotion on solid ground in dogs, horses, and humans. Quadrupedal species normally synchronize the locomotor and respiratory cycles at a constant ratio of 1:1 (strides per breath) in both the trot and gallop. Human runners differ from quadrupeds in that while running they employ several phase-locked patterns (4:1, 3:1, 2:1, 1:1, 5:2, and 3:2), although a 2:1 coupling ratio appears to be favored. Even though the evolution of bipedal gait has reduced the mechanical constraints on respiration in man, thereby permitting greater flexibility in breathing pattern, it has seemingly not eliminated the need for the synchronization of respiration and body motion during sustained running. Flying birds have independently achieved phase-locked locomotor and respiratory cycles. This hints that strict locomotor-respiratory coupling may be a vital factor in the sustained aerobic exercise of endothermic vertebrates, especially those in which the stresses of locomotion tend to deform the thoracic complex.