Trainability of Physical Function and Threshold Age for Decline in Frail Older Women: A 6-Year Community-Based Multicomponent Exercise Program

Japan is a super-aged society where community group multicomponent exercise is widely implemented, yet the age at which a fixed, low-frequency exercise dose no longer offsets functional decline is unclear. We examined 6-year trainability and explored “zero-change” ages in frail older women. Twenty community-dwelling frail women (80–86 years) participated in a once-weekly 90 min multicomponent exercise program for 6 years. Nine physical tests were assessed at baseline (Pre), 6 months, and annually. Overall time effects were tested using repeated-measures ANOVA and generalized estimating equations, with planned paired t-tests versus Pre. Age-specific annual percent changes (%/year) from Pre to each follow-up were annualized, grouped by age at follow-up (81–91 years), and tested against 0%/year. Separately, regression analyses related age to annual percent change across seven consecutive intervals to estimate “zero-change age” (predicted change = 0%). Time effects were significant for all nine measures (all p ≤ 0.032). Chair stand, 10 m fast/zigzag walk, supine-to-stand, maximal 5-step length, and 10-times knee lift generally improved in the early follow-up, whereas handgrip strength and sit-and-reach declined over time. In 6/9 tests, annual percent change diminished with advancing age; estimated zero-change ages ranged from ≈82 years (maximal 5-step length) to ≈88 years (chair stand and one-leg stance). Attendance remained high (≈90%). In this single-arm community program, several mobility-related functions improved or were maintained in frail women in their early 80s, whereas reduced trainability beyond the mid-80s may limit further protection. Threshold ages are exploratory statistical estimates; controlled trials are warranted.