Effects of High-Intensity Interval Training Versus High-Intensity Circuit Training on Airflow Limitation in Older Adults with Pre- COPD: A Pilot RCT

PURPOSE: Pre-COPD, characterized by mild airflow limitation, represents a critical window for preventing progression to chronic obstructive pulmonary disease (COPD). This pilot randomized controlled trial examined the effects of high-intensity interval training (HIIT) versus high-intensity circuit training (HICT) on pulmonary function in older adults with pre-COPD.METHODS: Twenty older men aged 60-75 years with pre-COPD, defined as normal or near-normal FEV1 with symptoms, risk factors, and mild airflow limitation (FEV1/FVC 0.70-0.95), were screened. Fourteen eligible participants were randomized to HIIT (n=7) or HICT (n=7) for a 9-week supervised intervention. Due to three HIIT dropouts, on-treatment analysis included 4 HIIT and 7 HICT participants. Primary outcomes were pulmonary function, with secondary measures of cardiopulmonary and functional fitness.RESULTS: Despite the limited sample size, significant time×group interactions were observed for FEV1/FVC ratio (p=.004, η²p =0.62) and FEV1 % predicted (p=.018, η²p =0.37). The HIIT group improved FEV1/FVC ratio (0.82±0.08 to 0.91±0.06, +11.0%) and FEV1 (91.4±15.2% to 98.7±14.8%, +8.0%), while the HICT group showed unexpected decrements (FEV1/FVC: 0.88±0.06 to 0.84±0.07, -4.5%; FEV1: 97.3±14.6% to 89.2±15.3%, -8.3%). Functional fitness improvements were observed exclusively in the HIIT group, with significant gains in lower extremity strength and aerobic endurance.CONCLUSIONS: This preliminary investigation indicates that HIIT may be associated with favorable changes in pulmonary function in older adults with pre-COPD, although these findings should be interpreted with caution. Given the limited sample size, the results primarily provide exploratory effect size estimates and feasibility data for future studies. The observed differences between HIIT and HICT underscore the need for further research on exercise prescription in this population.