Multimodal exercise programs can help mitigate or reverse age-related decrements in muscle size, muscle strength, physical function and balance, culminating in a reduced rate and risk of falls. Whether these improvements in response to exercise lead to increased physical activity levels or psychological outcomes is yet to be determined. This study sought to assess the effectiveness of an 18-week multimodal exercise program on objectively-measured physical activity, physiological (composite trunk muscle size and strength), and psychological functioning (fear of falls, anxiety, and depression) in healthy older adults. Using a single-blinded, parallel-group randomised controlled trial, older adults (≥60 years) were allocated to a 12-week exercise program comprising walking and balance exercises with or without trunk strengthening/motor control exercises; followed by a 6-week walking-only program. Primary outcome measures were physical activity (Hip-worn, triaxial GT3X Actigraph accelerometer), composite trunk muscle size (ultrasound), composite trunk strength (Humac NORM isokinetic dynamometer), fear of falling (Falls Efficacy Scale-International), anxiety (Geriatric Anxiety Inventory), and depression (Geriatric Depression Scale Short Form). Sixty-four older adults (mean (SD); age: 69.8 (7.5) years; 59.4% female) were recriuited and randomised (n=32 per group). Trunk strengthening training increased (mean difference [95%CI]) composite trunk muscle size (1.6 [1.0, 2.2] cm) and strength (171.1 [100.9, 241.3] N) relative to walking-balance training. There were no significant between group differences for physical activity and sedentary behaviour (accelerometry outcomes), perceived fear of falling, depression and anxiety following the 12-week exercise program. Detraining significantly decreased trunk muscle size and physical activity in the trunk strengthening exercise group, and caused slight declines in trunk strength and psychological functioning in both exercise groups. Together, these findings support the inclusion of trunk strengthening/motor control exercises in a multimodal exercise program was associated with improvements in composite trunk muscle size and strength, which were translated into some relatively small improvements in physical activity and reduction in sedentary behavior, and relatively small improvements in psychological functioning in healthy older adults.

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