Dataset Information

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 (V?E) and gas exchange (CO2 output (V?CO2) and O2 uptake (V?O2)) 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 V?E decreased sharply whereas the phase shift of V?E increased. In comparing walking and cycling at the equivalent metabolic demand, the amplitude of V?E 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 V?E amplitude ratio to V?CO2 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.

SUBMITTER: Fukuoka Y

PROVIDER: S-EPMC5226792 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in Humans.

Fukuoka Yoshiyuki Y Iihoshi Masaaki M Nazunin Juhelee Tuba JT Abe Daijiro D Fukuba Yoshiyuki Y

PloS one 20170111 1

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 ...[more]

PMID: 28076413

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Project description:New findingsWhat is the central question of the study? Ventilation increases during prolonged intense exercise, but the impact of dehydration and hyperthermia, with associated blunting of pulmonary circulation, and independent influences of dehydration, hyperthermia and sympathoadrenal discharge on ventilatory and pulmonary gas exchange responses remain unclear. What is the main finding and its importance? Dehydration and hyperthermia led to hyperventilation and compensatory adjustments in pulmonary CO2 and O2 exchange, such that CO2 output increased and O2 uptake remained unchanged despite the blunted circulation. Isolated hyperthermia and adrenaline infusion, but not isolated dehydration, increased ventilation to levels similar to combined dehydration and hyperthermia. Hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise, partly via sympathoadrenal activation.AbstractThe mechanisms driving hyperthermic hyperventilation during exercise are unclear. In a series of retrospective analyses, we evaluated the impact of combined versus isolated dehydration and hyperthermia and the effects of sympathoadrenal discharge on ventilation and pulmonary gas exchange during prolonged intense exercise. In the first study, endurance-trained males performed two submaximal cycling exercise trials in the heat. On day 1, participants cycled until volitional exhaustion (135 ± 11 min) while experiencing progressive dehydration and hyperthermia. On day 2, participants maintained euhydration and core temperature (Tc ) during a time-matched exercise (control). At rest and during the first 20 min of exercise, pulmonary ventilation ( V̇E${\skew2\dot V_{\rm{E}}}$ ), arterial blood gases, CO2 output and O2 uptake were similar in both trials. At 135 ± 11 min, however, V̇E${\skew2\dot V_{\rm{E}}}$ was elevated with dehydration and hyperthermia, and this was accompanied by lower arterial partial pressure of CO2 , higher breathing frequency, arterial partial pressure of O2 , arteriovenous CO2 and O2 differences, and elevated CO2 output and unchanged O2 uptake despite a reduced pulmonary circulation. The increased V̇E${\skew2\dot V_{\rm{E}}}$ was closely related to the rise in Tc and circulating catecholamines (R2 ≥ 0.818, P ≤ 0.034). In three additional studies in different participants, hyperthermia independently increased V̇E${\skew2\dot V_{\rm{E}}}$ to an extent similar to combined dehydration and hyperthermia, whereas prevention of hyperthermia in dehydrated individuals restored V̇E${\skew2\dot V_{\rm{E}}}$ to control levels. Furthermore, adrenaline infusion during exercise elevated both Tc and V̇E${\skew2\dot V_{\rm{E}}}$ . These findings indicate that: (1) adjustments in pulmonary gas exchange limit homeostatic disturbances in the face of a blunted pulmonary circulation; (2) hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise; and (3) sympathoadrenal activation might partly mediate the hyperthermic hyperventilation.

Dataset Information

Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in Humans.

Publications

Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in Humans.

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