A Simplified Strategy for the Estimation of the Exercise Ventilatory Thresholds

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Abstract

Purpose:

To analyze the limits of agreement between exercise ventilatory threshold values (VT1 and VT2) estimated from a combination of pulmonary gas exchange and ventilatory variables (cardiopulmonary exercise testing) and those derived from an alternative approach based on the ventilatory response only (JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE, ventilometry).

Methods:

Forty-two nontrained subjects (24 males, aged 18-48, peak JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngO2 = 33.1 ± 8.6 mL·min−1·kg−1) performed a maximum incremental cardiopulmonary exercise testing on an electromagnetically braked cycle ergometer. The participants breathed through a Pitot tube (Cardio2 System™, MGC) and a fixed-resistance ventilometer (Micromed, Brazil), which were connected in series. HR values at the estimated VT (VTHR1 and VTHR2) were obtained by the conventional method (ventilatory equivalents, end-expiratory pressures for O2 and CO2, and the V-slope procedure) and an experimental approach (JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE vs time, JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE/time vs time, and breathing frequency vs time).

Results:

There were no significant between-method differences on VTHR1, VTHR2, VTJOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE1, VTJOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE2, and peak JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngE (P> 0.05). After certification of data normality, a Bland-Altman analysis revealed that the mean bias ± 95% confidence interval of the between-method differences were lower for VTHR2 than VTHR1 (2 ± 9 and 0 ± 17 bpm, respectively). VTHR2 according to ventilometry differed more than 10 bpm from the standard procedure in 3 out of 42 subjects (9%). Between-method differences were independent of the level of fitness, as estimated from peak JOURNAL/mespex/04.02/00005768-200605000-00027/ENTITY_OV0312/v/2017-07-20T223028Z/r/image-pngO2 (P> 0.05).

Conclusions:

A simplified approach, based on the ventilatory response as a function of time, can provide acceptable estimates of the exercise ventilatory thresholds-especially VT2-during ramp-incremental cycle ergometry. This new strategy might prove to be useful for exercise training prescription in nontrained adults.

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