Two-Year Longitudinal Trajectory of Inspiratory and Expiratory Spirometric Parameters in a Professional Cyclist Cohort Under Ventilatory Strategy Training (VST): Descriptive Extension of a Published 48-Week Cohort

Background. Inspiratory and expiratory spirometric adaptations under the Ventilatory Strategy Training (VST) protocol were previously documented across 48 weeks in a cohort of ten professional cyclists (Ricci & Bouverot 2025, DOI 10.5281/zenodo.16645438). Whether these adaptations persist, progress, or regress beyond the initial protocol year has not been characterized. Objective. To describe the monthly trajectory of six spirometric parameters — three inspiratory (S Index, Peak Inspiratory Flow, inspiratory volume) and three expiratory (FEV₁, FEV₆, FEV₁/FEV₆ ratio) — across 24 months of continuous VST exposure in the same cohort, using aggregated cohort means. Methods. Aggregated monthly cohort means were compiled from baseline (T0) to 24 months of continuous protocol exposure, yielding 26 inspiratory and 25 expiratory data points. No inferential testing was conducted. Analysis was restricted to descriptive magnitudes and trajectory direction across three reference timepoints: T0, 48 weeks (end of year 1), and 24 months. Results. All five volume/force parameters (S Index, PIF, inspiratory volume, FEV₁, FEV₆) increased continuously across 24 months, with cumulative gains at 24 months exceeding those at 48 weeks (inspiratory: +22.0% to +31.6%; expiratory: +12.2% to +12.4%). Year-2 increments were positive on all five parameters (+1.5% to +3.8%). The FEV₁/FEV₆ ratio remained stable within the ≥0.83 optimal band across the full 24-month window. Conclusion. Static inspiratory and expiratory spirometric signatures continue to progress across the second year of VST exposure. This descriptive extension characterizes the trajectory of the mobilizable ventilatory substrate; the dynamic transposition of these adaptations into operational cycling performance is addressed in separate reports of the corpus.