Instrumental case study — Replication in a third WorldTour cyclist of the breathing-route sensitivity of the Tymewear Tidal/Tv ratio and local calibration of the Tidal signal by VO₂ Master Tv binning

Background. The Tymewear Vital Strap Pro (TWP) delivers a dimensionless Tidal signal reflecting the amplitude of thoracic deformation per cycle. Its conversion into tidal volume (Tv) requires an individual Tidal/Tv ratio, the breathing-route sensitivity of which has been established by Studies 1 to 4 of this series (Ricci 2025; 2026a–c) on two athletes and four contexts (outdoor ergometer at VT1, multi-condition field, high-intensity ergometer, field under exercise-induced bronchoconstriction). Within the Ventilatory Strategies Training (VST) programme, this ratio plays the role of a translation operator between the iTv/iRf prescription and the field observation on the Tymewear head unit — an indispensable operational condition for piloting the ventilatory pattern in real time. Methods. A professional cyclist (Ath-03, anonymised) was tested under outdoor conditions with simultaneous TWP and VO₂ Master Pro measurements during a Day 2 profiling session. The protocol comprised separate blocks under nasal breathing (Z2–Z3 intensity; 285–340 W) and mouth breathing (Z4–Z5; 340–390 W), each measurement aggregated over a one-minute stable window. n = 56 valid pairs (n = 22 nasal; n = 34 mouth). Analyses: full Bland-Altman for Rf (bias ± SD, 95% CI on the bias, LoA, PE%, ICC(2,1), Lin's CCC, Passing-Bablok regression); Hedges g effect sizes with 95% CI for the nasal vs mouth comparison; two-resolution binning (0.10 L and 0.25 L) of VO₂ Master Tv to characterise the local dispersion of Tymewear Tidal; linear Tidal = f(Tv) regression by route; cross-dataset convergence table over five independent datasets. Results. Global Rf accuracy: bias = -0.234 bpm 95% CI -0.388; -0.080, LoA -1.39; +0.92, PE = 4.01%, ICC = 0.9959, CCC = 0.9959; Passing-Bablok slope = 1.004, intercept = -0.202 bpm. Tidal/Tv ratio: nasal 101.03 ± 4.18 AU/L vs mouth 86.14 ± 3.54 AU/L; Δ = +14.89 AU/L (+17.3%); Hedges g = 3.863 95% CI 2.97; 4.76, very large magnitude; Welch t = 13.81, p = 1.03e-16. Local accuracy of the Tidal signal at fixed VO₂M Tv (0.10 L resolution): median within-bin CV of 3.40% under nasal and 2.85% under mouth breathing. The nasal > mouth direction is preserved without exception across the five datasets of the series (3 athletes, 4 contexts, including one under documented EIB). Conclusion. The breathing-route sensitivity of the Tymewear Tidal/Tv ratio is replicated in a third WorldTour cyclist with a very large magnitude (Hedges g > 3). The nasal > mouth direction converges across all 5 datasets of the VST Research series (3 independent athletes, 4 contexts), qualifying a STRONG level of evidence for the direction of the finding. The absolute magnitudes, which depend on mechanical context, retain an INTERMEDIATE status strictly within-subject. The local accuracy of Tidal at fixed Tv (median within-bin CV < 4% outside transition zones) is compatible with operational use as a biofeedback tool for the VST protocol under field conditions, subject to individual calibration. The Tymewear Tidal signal must be interpreted as a mechanical signature of the ventilatory pattern — operationally exploitable as a biofeedback tool for the VST protocol — and not as a direct estimate of lung volume. All results are individual (n = 1 athlete); no population-level generalisation is claimed.