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

Abstract

Purpose: To quantify the effects of prolonged cycling on the rate of ventilation (V ˙ E ), frequency of respiration (FR), and tidal volume (VT) 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 (VT1), before (PRE) and after (POST) two hours of moderate-intensity cycling. The power output, V ˙ E , FR, and VT associated with VT1 were determined PRE and POST. Results: As previously reported, power output at VT1 significantly decreased by ~ 10% from PRE to POST. The V ˙ E associated with VT1 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 V ˙ E associated with VT1 was produced with increased FR (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 VT (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 V ˙ E remains stable. Real-time monitoring of V ˙ E may be a useful means of assessing proximity to the moderate-to-heavy intensity transition during prolonged exercise and is worthy of further research.