Intermittent normobaric hypoxia at rest is associated with divergent cardiac autonomic trajectories in master cyclists

Figures

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  Fig. 1. CONSORT flow diagram. Flow of participants through the 2 × 2 randomized, participant-blinded, sham-controlled crossover trial. Twenty-four participants were randomized; one withdrew during Period 1 due to scheduling constraints. Twenty-three participants completed both periods and were included in the primary analyses

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  Fig. 2. Study design overview for the 2 × 2 crossover trial. Overview of the intervention sequences (IHNT→Sham; Sham→IHNT), 4-week washout, session structure (8 cycles of 4 min exposure interleaved with 4 min normoxic recovery), and HRV assessment blocks (10 consecutive morning recordings; days 4–10 averaged) at Baseline, Post-intervention, and Follow-up within each period

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  Fig. 3. RMSSD profile by condition × time. Model-estimated marginal means (EMMs) with 95% confidence intervals for RMSSD, back-transformed from lnRMSSD, at Baseline, Post-intervention, and Follow-up under IHNT and Sham. Estimates are from the prespecified REML linear mixed-effects model with an AR(1) residual structure and condition-specific heterogeneous residual variances. Symbols denote statistically significant within-condition changes versus Baseline based on nominal p values. No between-condition contrasts reached statistical significance after Holm–Bonferroni adjustment. ***p < 0.001

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  Fig. 4. HF power profile by condition × time. Model-estimated marginal means (EMMs) with 95% confidence intervals for HF power, back-transformed from lnHF, at Baseline, Post-intervention, and Follow-up under IHNT and Sham. Estimates are from the prespecified REML linear mixed-effects model with an AR(1) residual structure and condition-specific heterogeneous residual variances. Symbols denote statistically significant within-condition changes versus Baseline based on nominal p values. No between-condition contrasts reached statistical significance after Holm–Bonferroni adjustment. *p < 0.05; ***p < 0.001