Feasibility and effects of high-intensity interval training in older adults with mild to moderate depressive symptoms: A pilot cluster-randomized controlled trial

Background: Older adults with mild-to-moderate depressive symptoms (MMDS) are at high risk of developing severe depression along with mortality and disability. The aim of this study was to investigate the feasibility and preliminary effects of high-intensity interval training (HIIT) in older adults with MMDS in a small sample size. Methods: Three elderly centers involving 24 older adults with MMDS were randomized into: 1) HIIT (n = 8); 2) moderate-intensity continuous training (Baduanjin Qigong) (MICT-BDJ) (n = 8); or 3) recreation workshop (RW) control (n = 8) for 16-week (32 session) intervention. Feasibility was assessed using retention rate, session attendance rate, exercise intensity adherence, acceptability, and safety. Depressive symptoms were assessed using the Chinese version of the 15-item Geriatric Depression Scale, while physical fitness (PF) was measured using the Senior Fitness Test. Depressive symptoms and PF were evaluated at baseline and post-intervention. Results: 20 participants completed data collection twice. The retention rate was 87.5 % (7/8), 87.5 % (7/8), 75 % (6/8) for HIIT, MICT-BDJ, and RW, respectively. 87.5 % (7/8) of HIIT participants completed at least 75 % of exercise sessions. 81.4 % of HIIT participants achieved pre-designed intensity (≥80 % maximum heart rate) during high-intensity intervals. All HIIT (7/7) participants were satisfied with their group allocation. More HIIT (6/7) than MICT-BDJ (5/7) participants found exercise enjoyable. Two mild adverse events were reported in HIIT group. HIIT improved depressive symptoms more than MICT-BDJ (d = -1.02) and RW (d = -1.32). Both HIIT (d = 1.26) and MICT-BDJ (d = 1.39) improved PF more than RW. Conclusions: This study provides preliminary evidence on the feasibility and effect of HIIT for older adults with MMD. Both HIIT and MICT-BDJ improved depressive symptoms and PF. HIIT demonstrated better efficacy in depressive symptoms and mobility than MICT-BDJ. The findings should be interpreted cautiously due to several limitations. The rigorous cluster randomized controlled trial with large-scale sample size is warranted in the future to affirm the current findings. Trial registration: Trial Registration: NCT06014294.