Padilla-Pérez J

Language: English
References: 24
Page: 18-25
PDF size: 193.50 Kb.

ABSTRACT

We assessed in old healthy male volunteers if the fundamental VO₂ (Φ₂ VO₂) to submaximal exercise (ontransient response) and its recovery (offtransient response) show in the VO₂ kinetics (τ₂, time constant two) on-off symmetry (τ_2On vs. τ_2Off) characterised from best exponential fitting models previously assessed. Volunteers (n = 9; mean ± SD: 72 ± 4 yrs) completed an initial incremental ramp test (W·min-¹) to volitional fatigue from which the ventilatory threshold (θ) and work rates corresponding to 80%θ (ModRel) and 120%θ (HvyRel) were identified, plus a selected “absolute” work rate of 50 W (ModAbs) (submaximal exercise). On and off step-transitions in work rate were initiated from a baseline (BL) without warning to the subject. Each transition (On, Off) lasted 6 min and 4-6 transitions were performed at each intensity. The VO₂ response was measured breath-by-breath at BL and throughout each transition. On and off data were filtered, interpolated to 1-s intervals and ensemble-averaged to yield a single response profile for each subject and intensity. The averaged response for each subject was fit with a two- (2C), and three-component (3C) exponential model by using different fitting windows, and parameter (P) estimates (i.e., τ₂) were determined for each component. Our best statistically and/or physiologically fitting models showed symmetry τ₂ values for Mod with 2C, 7P (Mod_Abs and Rel: on = 57 ± 15 and off = 56± 14); and for HvyRel (on = 40 ± 9 y off = 39 ± 7) with 3C, 10P. BL (mL·min-¹) Hvyon (744 ± 115) was low compared Hvyoff (982 ± 288). Overall

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