Exuberant Claims for Exercise and Brain Health

“Exercise with a buddy, your brain will thank you,” says the Washington Post. “Improve Your Memory, Problem-Solving, and Mental Processing Speeds in Just 6 Minutes,” promises Inc. This is just a small sample of the exuberant claims about exercise and brain health coming at us from news media.

There’s only one problem. Some of it may be more fable than fact. An umbrella review in Nature Human Behavior this week examined evidence for a causal effect of exercise on brain health. The authors found it wanting.

24 Meta-Analyses of RCTs

Luis Ciria and colleagues reviewed 24 meta-analyses of RCTs for the effect of physical exercise on cognitive function. Yes, they found that most of these studies reported a positive overall effect.

A closer look revealed low statistical power in the primary RCTs, selective inclusion of studies, publication bias, large variation in pre-processing and analytic decisions. So the documented benefits got smaller after accounting for key moderators and then negligible with a correction for publication bias. Ciria et al concluded simpy:

“These findings suggest caution in claims and recommendations linking regular physical exercise to cognitive benefits in the healthy human population until more reliable causal evidence accumulates.”

Certainly, exercise is beneficial for health. But it might not be the magic tonic for brain health that headlines keep suggesting.

Exuberance Meets Science

If you need a refresher on the enthusiastic supporters of exercise, just have a listen to Robert Preston’s Chicken Fat song. But enthusiasm is no substitute for scientific rigor. A recent analysis by David Borg and colleagues found “an excess of published research with statistically significant results just below the standard significance threshold of 0.05, which is indicative of publication bias.”

Nicholas Tiller, John Sullivan, and Panteleimon Ekkekakis described the problem recently in Sports Medicine. Baseless claims and pseudoscience promote the interests of a lucrative physical activity and wellness industry. They call for greater rigor and offer exercise scientists an important warning:

“Pseudoscience in health and wellness, if left unchecked and unchallenged, may have profound implications for the reputation of exercise science as a discipline.”

Click here for the review by Ciria et al, here for the analysis by Borg et al, and here for the viewpoint by Tiller, Sullivan, and Ekkekakis.

Bend Trunk Forward to Right Angle, illustration from 1922 Manual for Physical Training in Elementary Schools / Wikimedia Commons

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March 31, 2023