There is a strong link between the practice of regular physical exercise and maintenance of cognitive brain health. Animal and human studies have shown that exercise exerts positive effects on cognition through a variety of mechanisms, such as changes in brain volume and connectivity, cerebral perfusion, synaptic plasticity, neurogenesis, and regulation of trophic factors. However, much of this data has been conducted in young humans and animals, raising questions regarding the generalizability of these findings to aging adults. Furthermore, it is not clear at which doses these effects might take place, and if effects would differ with varying exercise modes (such as aerobic, resistance training, combinations, or other). The purpose of this review is to summarize the evidence on the effects of exercise interventions on various mechanisms believed to support cognitive improvements: cerebral perfusion, synaptic neuroplasticity, brain volume and connectivity, neurogenesis, and regulation of trophic factors. We synthesized the findings according to exposure to exercise (short-[1 day-16 weeks], medium-[24-40 weeks], and long-term exercise [52 weeks and beyond]) and have limited our discussion of dose effects to studies in aging adults and aged animals (when human data was not available).

We found that exercising for at least 52 hours is associated with improved cognitive performance in older adults with and without cognitive impairment. Exercise modes supported by evidence are aerobic, resistance (strength) training, mind-body exercises, or combinations of these interventions.