Effects of a 12-week time-of-day-specific concurrent resistance-aerobic training on muscle strength, bone mass and...

Diurnal strength fluctuations and the effects of time-of-day-specific training are well-documented in young adults but unclear in elderly women. This study investigated the effects of time-of-day-specific concurrent resistance-aerobic training on muscle strength, bone mass, and functional performance in elderly women. Twenty-six women (65-85 years) were randomized into morning (MTG), afternoon (ATG) and control (CON) groups. Training groups completed 12 weeks of concurrent resistance-aerobic training (3 sessions/week, factor of time). Outcomes included maximal knee extension torque (measured AM/PM, factor of test time), bone mineral density (DXA), and functional tests (30-s chair stand, Five Times Sit-to-Stand and Maximal gait speed). Analysis of strength confirmed a preserved diurnal rhythm, with morning performance deficit present (test time: p=0.0129). The group and time factors interaction approached significance (p=0.0624), further test showed that only ATG differed significantly from the CON, with broader improvement than MTG. The functional performance significantly improved in all tests (p<0.0001, p=0.0002, p=0.0200, respectively) compared to baseline, with no difference between groups. The bone mass parameters remained unchanged. The time-of-day-specific concurrent training improved strength and functional performance in both training groups with afternoon training producing superior strength gains compared to morning training. Unchanged bone parameters suggest longer interventions might be needed for osteogenic effects.