Tidal/VT Calibration of the Tymewear Vital Strap Pro Under VST Protocol: Nasal vs. Buccal Route Effects Replicated Across Three Outdoor Studies

Background: The Tymewear Vital Strap Pro (TWP) generates a dimensionless Tidal signal reflecting thoracic strain amplitude per respiratory cycle. Its conversion to tidal volume (VT) requires an individual Tidal/VT ratio sensitive to breathing route. Two prior studies established this: Study 1 (Ricci, 2025; doi:10.5281/zenodo.18667689) documented a +18.8% nasal vs. oral Tidal signal increase at VT1. Study 2 (Ricci, 2026a; doi:10.5281/zenodo.18873288) formalised a four-level hierarchical model (breathing route > position > bicycle type > intensity) with a large nasal vs. oral effect in TT bar position (d=1.06, Δ=+8.7 AU/L). The present study extends this series to an outdoor high-intensity ergometer protocol in a VST-conditioned World Tour cyclist. Methods: One World Tour cyclist (Ath-02; VST ≥2 months) was tested simultaneously with TWP and VO₂ Master Pro across two outdoor sessions (Day J; Day J+1). n=59 total pairs; 1 mixed-route pair excluded → n=58 valid pairs. Conditions: nasal and buccal breathing, 285–455W. Full Bland-Altman analysis; Hedges g; Mann-Whitney U; Welch t (α=0.05). Results: Global RF accuracy (n=58): bias=+0.187 bpm [±0.156], SD=0.607, LoA=[−1.003; +1.377], PE=4.1%, ICC=0.9980. Tidal/VT ratio: nasal 100.32±5.72 AU/L vs. buccal 85.64±2.98 AU/L; Δ=+14.68 AU/L; Hedges g=3.21 (very large); p=6.68×10⁻¹¹. Buccal route was inter-session stable (g=−0.55, p=0.14). Nasal route showed a moderate Day J to J+1 decrease (g=0.93, p=0.022), attributed to strap repositioning (~5 AU/L). Conclusion: The nasal amplification effect (Δ=+14.68 AU/L, g=3.21) is convergent across three studies (Δ: +11.5 to +14.7 AU/L; d/g: 1.06 to 3.21) in different contexts, athletes, and intensity ranges. Buccal inter-session stability confirms its role as calibration anchor. All results are individual (n=1 athlete); no population generalisation is claimed