Regular physical activity may boost the brain's glymphatic system, a waste-removal pathway that helps clear amyloid-beta and tau, the two toxic proteins that accumulate in Alzheimer's disease.
That is the central conclusion of a review published in Trends in Neurosciences, led by Dr. James Broatch and colleagues at Victoria University in Melbourne.
The glymphatic system is the brain's cleaning crew.
Cerebrospinal fluid moves along blood vessels and washes through brain tissue, carrying metabolic waste out with it.
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Most of that work happens during sleep.
The trouble is that amyloid-beta and tau are among the proteins the system is meant to remove.
When clearance falters, they build up in tissue. And the system tends to become more important, and less efficient, with age.
Where exercise fits in
The Victoria University team pulled together animal and human research and identified several ways exercise appears to support glymphatic flow.
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Regular training lowers blood pressure and reduces vascular stiffness, so the arteries pulsing next to those clearance pathways work more effectively.
Exercise also lowers resting norepinephrine, a stress-related chemical that constricts the space between brain cells and slows fluid movement.
Physical activity is linked to less brain inflammation and improved neuron activation as well.
Then there is sleep. Aerobic training tends to increase deep sleep and slow-wave activity, the sleep stage most tied to waste clearance.
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What the human data shows
The review points to one long-term human trial that measured the effect directly.
In a study published in Nature Communications in April 2025, researchers at Seoul National University used contrast-enhanced MRI to track glymphatic flow in healthy adults before and after 12 weeks of training on a cycle ergometer.
Putative glymphatic influx rose significantly in the putamen, a deep brain region, and flow through the meningeal lymphatic vessels around the brain increased as well.
Broatch emphasized that without regular opportunities for the brain to clear out metabolic waste, that buildup becomes damaging over time, particularly as people age.
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He noted that sleep plays a central role in that process, but that good quality sleep tends to become harder to achieve in older age.
The review was partly motivated by the question of whether exercise could help fill that gap.
What the review does not settle
The Trends in Neurosciences paper is a review, not a clinical trial in Alzheimer's patients.
It maps out plausible biological mechanisms and calls for more direct human evidence.
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The authors flag several unknowns, including how much exercise is needed, which activities work best, and whether recommendations should differ for people already showing cognitive decline or diagnosed with a brain disease.
For now, the practical takeaway is modest.
Aerobic movement that raises the heart rate, done regularly, is the type of activity most closely tied to the changes described in the review.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.