February 1, 1977Journal of Applied Physiology204 citations
View Full PaperVentilatory and gas exchange dynamics in response to sinusoidal work
Key Result
Sinusoidal work on a cycle ergometer yielded time constants for VE, VCO2, VO2, and HR averaging 1.4, 1.2, 0.8, and 0.8 min, respectively, with VE and VCO2 strongly correlated (r = 0.97).
Structured PICO
P
Population
5 subjects who exercised on a cycle ergometer for 30 minutes at sinusoidally fluctuating work rates.
I
Intervention
Exercise on a cycle ergometer for 30 min at work rates fluctuating sinusoidally between 25 W and 80% of the anaerobic threshold at sinusoidal periods of 0.7, 1, 2, 4, 6, and 10 min
O
Outcome
Amplitude and phase relations between ventilation/gas exchange variables (VE, VCO2, VO2, HR) and perturbing work loadsurrogate
Exercise hyperpnea appears linked to metabolism via carbon dioxide production, as evidenced by strongly correlated time constants for ventilation and CO2 production during sinusoidal exercise.
Main Result
Effect estimate: r = 0.97
Abstract
The dynamic relationships between ventilation and gas exchange variables during exercise were determined utilizing frequency analysis techniques. Five subjects exercised on a cycle ergometer for 30 min at work rates which fluctuated sinusoidally between 25 W and 80% of the anaerobic threshold at sinusoidal periods of 0.7, 1,2,4,6, and 10 min. VE, VCO2, VO2, and HR were computed and displayed breath-by-breath. From these and steady-state response data, digital computer routines extracted amplitude and phase relations between each variable and the perturbing work load. These response characteristics were well described by first-order linear dynamics with time constants for VE, VCO2, VO2, and HR averaging 1.4, 1.2, 0.8, and 0.8 min, respectively. The time constants of VE and VCO2 were strongly correlated among subjects (r = 0.97). Further, there was no evidence that neural afferents from the exercising limbs induced fast components in the ventilatory response to these forcings. These results are consistent with the hypothesis that exercise hyperpnea is linked to metabolism via carbon dioxide production.