Brawn may also boost brain power
February 9th 2011 19:45
IT HAS long been a cliche that muscle bulk doesn't equate with intelligence. Most of the science about activity and brain health has focused on the role of endurance exercise in improving brain functioning.
Aerobic exercise causes a steep spike in blood movement to the brain, an action some researchers speculated might be necessary to create new brain cells, or neurogenesis.
Running and other forms of aerobic exercise have been shown, in mice and men, to lead to neurogenesis in the parts of the brain associated with memory and thinking, providing another compelling reason to run.
Advertisement: Story continues below Few researchers thought muscle bulk would have a similar effect. But recent studies intimate otherwise. It's not easy to induce a lab rat to lift weights, so researchers developed clever approximations of resistance training to see what impact adding muscle and strength has on an animal's brain.
In a study presented at a meeting of the Society for Neuroscience, researchers from Brazil secured weights to the tails of rats and had them climb a ladder five times a week. Other rats on the same schedule ran on a treadmill and a third group just sat around. After eight weeks, the running rats had much higher levels of brain-derived neurotrophic factor (BDNF), a growth factor thought to help spark neurogenesis, than the sedentary rats. So did those with weights tied to their tails.
The weight-bearing rats, like the runners, did well in learning and memory tests, such as rapidly negotiating a water maze. Both endurance and weight training seemed to make the rats smarter.
Japanese researchers also recently found that loading the running wheels of animals improved their brain functioning.
A loaded running wheel is not strictly analogous to weightlifting; it's more similar in human terms to a stationary bicycle with the resistance dialled high - in this case, quite high, as the resistance equalled 30 per cent of the rats' body weights in the last week of the month-long study. By then, the rats on the loaded wheels could run barely half as far as a separate group of rats on unloaded wheels but those on the loaded wheels had packed on muscle mass, unlike the others. The animals that were assigned to the loaded wheels showed significantly increased levels of gene activity and BDNF levels in their brains. The higher the workload the animals managed to complete, the greater the genetic activity within their brains.
This study ''demonstrates voluntary wheel running with a load increases a muscular adaptation and enhances gene expression'' in the rat brain, says a researcher at the University of Tsukuba in Japan and the lead author of the study, Min-Chul Lee. Even more striking is that the findings indicate ''this kind of exercise may have the identical or even more useful effects than endurance training (eg treadmill exercise) on the rat brain''. Whether the same mechanisms occur in humans who undertake resistance training is not yet clear but the data ''looks promising,'' says a principal investigator at the Brain Research Centre at the University of British Columbia, Teresa Liu-Ambrose.
In results from her lab, older women who lifted weights performed significantly better on various tests of cognitive functioning than women who completed toning classes.
Liu-Ambrose has also done brain scans of people who lifted weights to test whether neurogenesis is occurring in their brains and the results are encouraging, she says.
Just how resistance training initiates changes in cognition remains a mystery. Liu-Ambrose says ''we now know resistance training has significant benefits on cardiovascular health'' and reduces ''cardiovascular risk factors'' that otherwise would raise ''one's risk of cognitive impairment''. She speculates that resistance training, by strengthening the heart, improves blood flow to the brain generally, which is associated with better cognitive function.
Perhaps almost as important, she says, resistance training at first requires an upsurge in brain usage.
The New York Times Magazine
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