VO2, Q and muscular deoxyhaemoglobin (HHb) kinetics were determined in 14 healthy male subjects at the onset of constant-load cycling exercise performed at 80% of the ventilatory threshold (80%VT) and at 120% of VO2max (120%Wmax). An innovative approach was applied to calculate the time constant (τ2) of the primary phase of VO2 and Q kinetics at 120%Wmax. Data were linearly interpolated after a semilogarithmic transformation of the difference between required/steady state and measured values. Furthermore, VO2, Q and HHb data were fitted with traditional exponential models. τ2 of VO2 kinetics was longer (62.5 ± 20.9 s) at 120%Wmax than at 80%VT (27.8 ± 10.4 s). The τ2 of Q kinetics was unaffected by exercise intensity and, at 120% of VO2max it was significantly faster (τ2 = 35.7 ± 28.4 s) than that of VO2 response. The time delay of HHb kinetics was shorter (4.3 ± 1.7 s) at 120%Wmax than at 80%VT (8.5 ± 2.6 s) suggesting a larger mismatch between O2 uptake and delivery at 120%Wmax. These results suggest that VO2 at the onset of exercise is not regulated/limited by muscle’s O2 utilisation and that a slower adaptation of capillary perfusion may cause the deceleration of VO2 kinetics observed during supramaximal exercise.

Oxygen uptake, cardiac output and muscle deoxygenation at the onset of moderate and supramaximal exercise in humans.

ADAMI, Alessandra;POGLIAGHI, Silvia;DE ROIA, Gabriela Fernanda;CAPELLI, Carlo
2011-01-01

Abstract

VO2, Q and muscular deoxyhaemoglobin (HHb) kinetics were determined in 14 healthy male subjects at the onset of constant-load cycling exercise performed at 80% of the ventilatory threshold (80%VT) and at 120% of VO2max (120%Wmax). An innovative approach was applied to calculate the time constant (τ2) of the primary phase of VO2 and Q kinetics at 120%Wmax. Data were linearly interpolated after a semilogarithmic transformation of the difference between required/steady state and measured values. Furthermore, VO2, Q and HHb data were fitted with traditional exponential models. τ2 of VO2 kinetics was longer (62.5 ± 20.9 s) at 120%Wmax than at 80%VT (27.8 ± 10.4 s). The τ2 of Q kinetics was unaffected by exercise intensity and, at 120% of VO2max it was significantly faster (τ2 = 35.7 ± 28.4 s) than that of VO2 response. The time delay of HHb kinetics was shorter (4.3 ± 1.7 s) at 120%Wmax than at 80%VT (8.5 ± 2.6 s) suggesting a larger mismatch between O2 uptake and delivery at 120%Wmax. These results suggest that VO2 at the onset of exercise is not regulated/limited by muscle’s O2 utilisation and that a slower adaptation of capillary perfusion may cause the deceleration of VO2 kinetics observed during supramaximal exercise.
2011
Oxygen uptake kinetics; Cardiac output kinetics; Near-infrared spectroscopy; Severe intensity exercise; Mathematical modelling; Gas exchanges
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11562/347314
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