title: Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in Humans.
abstract: Our present study investigated whether the ventilatory and gas exchange responses show different dynamics in response to sinusoidal change in cycle work rate or walking speed even if the metabolic demand was equivalent in both types of exercise. Locomotive parameters (stride length and step frequency), breath-by-breath ventilation (V̇E) and gas exchange (CO2 output (V̇CO2) and O2 uptake (V̇O2)) responses were measured in 10 healthy young participants. The speed of the treadmill was sinusoidally changed between 3 km·h-1 and 6 km·h-1 with various periods (from 10 to 1 min). The amplitude of locomotive parameters against sinusoidal variation showed a constant gain with a small phase shift, being independent of the oscillation periods. In marked contrast, when the periods of the speed oscillations were shortened, the amplitude of V̇E decreased sharply whereas the phase shift of V̇E increased. In comparing walking and cycling at the equivalent metabolic demand, the amplitude of V̇E during sinusoidal walking (SW) was significantly greater than that during sinusoidal cycling (SC), and the phase shift became smaller. The steeper slope of linear regression for the V̇E amplitude ratio to V̇CO2 amplitude ratio was observed during SW than SC. These findings suggested that the greater amplitude and smaller phase shift of ventilatory dynamics were not equivalent between SW and SC even if the metabolic demand was equivalent between both exercises. Such phenomenon would be derived from central command in proportion to locomotor muscle recruitment (feedforward) and muscle afferent feedback.
authors.affiliation: Laboratory of Environmental Physiology, Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan.|Laboratory of Environmental Physiology, Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuoka
authors.affiliation: Laboratory of Environmental Physiology, Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Iihoshi
authors.affiliation: Laboratory of Environmental Physiology, Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan.
authors.forename: Juhelee Tuba
authors.initials: JT
authors.lastname: Nazunin
authors.affiliation: Biodynamics Laboratory, Center for Health and Sports Science, Kyushu Sangyo University, Fukuoka, Japan.
authors.forename: Daijiro
authors.initials: D
authors.lastname: Abe
authors.affiliation: Department of Sports Science and Physiology, Hiroshima Prefectural University, Hiroshima, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuba
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D016138:Walking / Q000502:physiology*