Distributed stair-climbing exercise snacks versus task-matched concentrated stair climbing in office workers: a 12-week three-arm randomized controlled trial

Background Prolonged occupational sitting and insufficient physical activity are important concerns in workplace health promotion. Brief stair-climbing exercise snacks may provide a time-efficient approach for increasing physical activity during the workday, but whether distributing task-matched bouts improves adherence remains unclear. Methods In this 12-week, three-arm randomized trial, 135 insufficiently active office workers were assigned to distributed stair climbing ( n = 50), concentrated stair climbing ( n = 50), or usual-lifestyle control ( n = 35). Both active groups completed three 56-step ascents on four workdays per week. Distributed bouts were separated by ≥2 h, whereas concentrated bouts were completed in one session with approximately 2 min recovery. The primary outcome was the proportion of 48 planned days with complete prescriptions, analyzed using beta-binomial regression adjusted for site, sex, and age. Week-12 outcomes were exploratory and analyzed using baseline-adjusted ANCOVA. Results All 100 active participants entered the primary analysis. Adjusted adherence was 76.3% (95% CI, 73.6–78.8%) for distributed scheduling and 71.1% (68.2–73.8%) for concentrated scheduling, with a between-group difference of 5.18 percentage points (1.39–8.97; p = 0.0074). Among completed bouts, distributed scheduling was associated with smaller increases in perceived exertion and completion time across bouts (interaction p < 0.001). At week 12, distributed scheduling was associated with faster 2-km walk time than control (−16.31 s; 95% CI, −31.74 to −0.88; p = 0.034), whereas other between-group contrasts were not significant. Exploratory analyses suggested favorable responses in postwalk heart rate, heart-rate recovery, and walk RPE, without clear effects on anthropometric or resting cardiometabolic outcomes. Among active participants, 132 safety events were recorded, including 120 mild and 12 moderate events, with no severe or serious adverse events. Conclusion Distributing task-matched stair-climbing bouts across the workday improved planned-day adherence by approximately five percentage points among insufficiently active office workers. Within-day scheduling may be considered when designing workplace physical activity programs. Further studies should evaluate workplace implementation, safety monitoring, and broader occupational health outcomes using prospectively registered protocols and objective adherence monitoring.