Pulmonary O₂uptake kinetics as a determinant of high-intensity exercise tolerance in humans

Abstract

Tolerance to high-intensity constant-power (P) exercise is well described by a hyperbola with two parameters: a curvature constant (W') and power asymptote termed "critical power" (CP). Since the ability to sustain exercise is closely related to the ability to meet the ATP demand in a steady state, we reasoned that pulmonary O(2) uptake (Vo(2)) kinetics would relate to the P-tolerable duration (t(lim)) parameters. We hypothesized that 1) the fundamental time constant (τVo(2)) would relate inversely to CP; and 2) the slow-component magnitude (ΔVo(2sc)) would relate directly to W'. Fourteen healthy men performed cycle ergometry protocols to the limit of tolerance: 1) an incremental ramp test; 2) a series of constant-P tests to determine Vo(2max), CP, and W'; and 3) repeated constant-P tests (WR(6)) normalized to a 6 min t(lim) for τVo(2) and ΔVo(2sc) estimation. The WR(6) t(lim) averaged 365 ± 16 s, and Vo(2max) (4.18 ± 0.49 l/min) was achieved in every case. CP (range: 171-294 W) was inversely correlated with τVo(2) (18-38 s; R(2) = 0.90), and W' (12.8-29.9 kJ) was directly correlated with ΔVo(2sc) (0.42-0.96 l/min; R(2) = 0.76). These findings support the notions that 1) rapid Vo(2) adaptation at exercise onset allows a steady state to be achieved at higher work rates compared with when Vo(2) kinetics are slower; and 2) exercise exceeding this limit initiates a "fatigue cascade" linking W' to a progressive increase in the O(2) cost of power production (Vo(2sc)), which, if continued, results in attainment of Vo(2max) and exercise intolerance. Collectively, these data implicate Vo(2) kinetics as a key determinant of high-intensity exercise tolerance in humans.

Influence of blood flow occlusion on muscle oxygenation characteristics and the parameters of the power-duration relationship

“…The results of the present study lend credence to W= not being determined by a finite amount of work per se, but rather by other mechanisms such as the rate of attainment of "limiting" muscle metabolic perturbations (7,21,28,43,51), the magnitude of the severe domain (5,51), and/or the V O 2 slow component (40). Modeling the present data reveals that, while W= is utilized in its entirety for exercise intensities above CP, the proportion of W= that contributes directly to external work is not constant across this range of power outputs (Fig.…”

Cinética do VO2 durante o exercício realizado na potência crítica em ciclistas e indivíduos não-treinados no ciclismo

“…Leclair et al (2008) max e, assim, também considerado pelos autores como uma resposta no domínio pesado do exercício. A resposta mais rápida do VO 2 no início do exercício e a menor amplitude do CL no exercício severo estão associadas à maior tolerância ao exercício (i.e., maior tempo de exaustão) (MURGATROYD et al, 2011). No entanto, nas condições de intensidade neste estudo, não houve diferença no t Lim entre os grupos.…”

Resposta Fisiológica E Perceptual Na Velocidade Crítica E Ponto De Compensação Respiratória

“…: moderado, pesado e severo), o exercício pesado é caracterizado pela maior intensidade do exercício que não está associado ao acúmulo de metabólitos, sendo a perturbação da homeostase muscular e sanguínea por acidose um evento fisiológico associados ao exercício acima deste domínio 1,2 . Tradicionalmente, esse limite é demarcado pela inclinação da relação hiperbólica entre intensidade do esforço e sua tolerância (tempo limite, t Lim ): a velocidade crítica (VC), ou potência crítica (PC) 1 .…”