Prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition

Abstract

Abstract Purpose To quantify the effects of prolonged cycling on the rate of ventilation ( $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> ), frequency of respiration (F R ), and tidal volume (V T ) associated with the moderate-to-heavy intensity transition. Methods Fourteen endurance-trained cyclists and triathletes (one female) completed an assessment of the moderate-to-heavy intensity transition, determined as the first ventilatory threshold (VT 1 ), before (PRE) and after (POST) two hours of moderate-intensity cycling. The power output, $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> , F R , and V T associated with VT 1 were determined PRE and POST. Results As previously reported, power output at VT 1 significantly decreased by ~ 10% from PRE to POST. The $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> associated with VT 1 was unchanged from PRE to POST (72 ± 12 vs. 69 ± 13 L . min −1 , ∆ − 3 ± 5 L . min −1 , ∆ − 4 ± 8%, P = 0.075), and relatively consistent (within-subject coefficient of variation, 5.4% [3.7, 8.0%]). The $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> associated with VT 1 was produced with increased F R (27.6 ± 5.8 vs. 31.9 ± 6.5 breaths . min −1 , ∆ 4.3 ± 3.1 breaths . min −1 , ∆ 16 ± 11%, P = 0.0002) and decreased V T (2.62 ± 0.43 vs. 2.19 ± 0.36 L . breath −1 , ∆ − 0.44 ± 0.22 L . breath −1 , ∆ − 16 ± 7%, P = 0.0002) in POST. Conclusion These data suggest prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition, but $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> remains stable. Real-time monitoring of $${\dot{\text{V}}}_{{\text{E}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> <mml:mtext>E</mml:mtext> </mml:msub> </mml:math> may be a useful means of assessing proximity to the moderate-to-heavy intensity transition during prolonged exercise and is worthy of further research.

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