Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in HumansReport as inadecuate




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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.



Author: Yoshiyuki Fukuoka , Masaaki Iihoshi, Juhelee Tuba Nazunin, Daijiro Abe, Yoshiyuki Fukuba

Source: http://plos.srce.hr/



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