Parameters of ventilatory and gas exchange dynamics during exercise

Abstract

To determine the precise nonsteady-state characteristics of ventilation (VE), O2 uptake (VO2), and CO2 output (VCO2) during moderate-intensity exercise, six subjects each underwent eight repetitions of 100-W constant-load cycling. The tests were preceded either by rest or unloaded cycling ("0" W). An early component of VE, VO2, and VCO2 responses, which was obscured on any single test by the breath-to-breath fluctuations, became apparent when the several repetitions were averaged. These early responses were abrupt when the work was instituted from rest but were much slower and smaller from the 0-W base line and corresponded to the phase of cardiodynamic gas exchange. Some 20 s after the onset of the work a further monoexponential increase to steady state occurred in all three variables, the time constants of which did not differ between the two types of test. Consequently, the exponential behavior of VE, VO2, and VCO2 in response to moderate exercise is best described by a model that incorporates only the second phase of the response.

Oxygen uptake kinetics as a determinant of sports performance

“…An abrupt change in these variables, in addition to an increase in V O 2 that continues in an exponential fashion, signals the onset of the next phase of the V O 2 response, which ultimately leads to the attainment of a steady state. A crucial question, only recently answered, is whether this second period, variously named the fundamental, primary, or fast component (Phase II), reflects the kinetics of muscle oxygen uptake, as was originally proposed by Whipp and colleagues (Whipp, Ward, Lamarra, Davis, & Wasserman, 1982) and Barstow et al . (1990)?…”

The effects of age on kinetics of oxygen uptake and phosphocreatine in humans during exercise

“…As with the 31p MRS tests, transients were from loadless exercise, as opposed to rest. This minimizes the phase 1 (early cardiodynamic) portion of the V'02 response (Whipp, Ward, Lamarra, Davis & Wasserman, 1982). Subjects were blinded to changes in load to minimize anticipatory responses.…”

Oxygen Uptake Estimation in Humans During Exercise Using a Hammerstein Model

“…After that, many papers attempt to capture both the exact time course of these kinetic adjustments and the physiological events governing the rate of adjustment. Most of them 32,46 approximate the process by using first order linear models, which were often obtained by using step change responses. Hoffmann et al 14,23 applied PRBS and sinewave signals to bicycle exercises.…”