Yoga-based breathing exercises performed in a salt-cave environment versus a standard clinical setting in smokers: a randomized controlled trial salt-cave breathing exercises in smokers

Backgorund To investigate the effect of a speleotherapy environment on spirometric parameters in smokers and to compare the outcomes with those of the same yoga-based breathing exercise program performed in a standard clinical setting. Methods This randomized controlled clinical trial included 60 adult smokers aged 18–65 years who were allocated to a speleotherapy group ( n = 30) or a control group ( n = 30). Both groups received the same physiotherapist-supervised yoga-based breathing exercise program for 6 weeks, twice weekly, in 50-minute sessions; the only difference was the intervention setting. Forced vital capacity, forced expiratory volume in 1 s, peak expiratory flow, and forced expiratory volume in 1 s/forced vital capacity were assessed at baseline, week 3, and week 6. Physical activity, functional exercise capacity, and quality of life were also evaluated. Data were analyzed using linear mixed-effects models with group, time, and group × time interaction as fixed effects and participant as a random effect. Results Both groups showed improvements over time in spirometric and secondary outcomes. In the linear mixed-effects model analysis, the primary spirometric outcome, forced expiratory volume in 1 s, showed a significant group × time interaction in favor of the speleotherapy group. Significant group × time effects were also observed for 6-minute walk distance and selected quality-of-life domains, whereas broader spirometric superiority across forced vital capacity, peak expiratory flow, and forced expiratory volume in 1 s/forced vital capacity was limited. Conclusion The findings suggest that the treatment environment may influence selected respiratory and functional outcomes in smokers. Yoga-based breathing exercises were associated with improvements in spirometric outcomes in both settings. The additional effect of the salt-cave environment on respiratory outcomes was limited, with a significant between-group difference observed only for forced expiratory volume in 1 s. The salt-cave setting may also be associated with greater improvements in functional capacity and selected quality-of-life outcomes, but broader pulmonary benefits or an independent speleotherapy effect cannot be concluded from the present findings. Trial registration ClinicalTrials.gov, NCT07737587. Retrospectively registered on 30 July 2026.