Pumping iron to sculpt your biceps. Yoga poses to stretch and relax. Running to build your endurance. There are loads of reasons why it’s smart to exercise, and most of us are familiar with the menu of options and how each can shape and benefit your body. But we are discovering that there are numerous ways in which exercise makes you smart too. Many of its effects have been going unnoticed, but if you were to peer inside the heads of people who like to keep active, you’d see that different exercises strengthen, sculpt and shape the brain in myriad ways.
That the brains of exercisers look different to those of their more sedentary counterparts is, in itself, not new. We have been hearing for years that exercise is medicine for the mind. Physical fitness has been shown to help with the cognitive decline associated with dementia, Parkinson’s disease and depression, and we know this is at least in part because getting your blood pumping brings more oxygen, growth factors, hormones and nutrients to your brain, leading it — like your muscles, lungs and heart — to grow stronger and more efficient.
But a new chapter is beginning in our understanding of the influence of physical exercise on cognition. Researchers are starting to find more specific effects related to different kinds of exercise. Specifically, weight training, high-intensity intervals, aerobic exercise, yoga and sports drills affect different areas of the brain.
Researchers are looking beyond the standard recommendation of 30 minutes of moderate exercise for the sake of your brain. Are there benefits to going slower or faster? To lifting weights, or performing sun salutations? Whether you want a boost in focus for an exam, find it hard to relax, or are keen to quit smoking, there’s a prescription for you.
The first clue that exercise affects the brain came from studies 15 years ago. Older adults who did aerobic exercise three times a week for a year grew larger hippocampi and performed better in memory tests. Those with the highest levels of brain-derived neurotrophic factor (BDNF) in their blood, which promotes the growth of new neurons, had the biggest increases in this brain region.
The idea that exercise helps to improve memory has been especially welcome. The search for effective treatments for cognitive decline has been slow in progress. It now seems that aerobic exercise may help stave off Alzheimer’s disease and other forms of dementia.
As the evidence for aerobic exercise accumulated, Teresa Liu-Ambrose at the University of British Columbia in Vancouver, Canada, began to wonder about other types of exercise. She has been looking for ways to halt dementia in people with mild cognitive impairment (MCI), a population of adults known to be at increased risk of developing dementia, and was especially interested in strength training, which has in recent years been added to US and UK government recommendations for physical activity.
To test the idea, Liu-Ambrose compared the effects of aerobic exercise and strength training in women with MCI. She measured their impact on two abilities known to decline as the condition progresses: memory and executive function — which encompasses complex thought processes, including reasoning, planning, problem-solving and multitasking.
Twice a week for an hour, one group lifted weights, while the other went for brisk walks quick enough that talking required effort. A control group just stretched for an hour instead. After six months of this, both walking and lifting weights had a positive effect on spatial memory — the ability to remember one’s surroundings and sense of place. On top of that, each exercise had unique benefits. The group that lifted weights saw significant improvements to executive function. They also performed better in tests of associative memory, which is used for things like linking someone’s name to their face. The aerobic-exercise group saw improvements to verbal memory — the ability to remember that word you had on the tip of your tongue. Simply stretching had no effect on either memory or executive function.
If aerobic exercise and strength training have distinct benefits, is combining them the way to go? To address this, Willem Bossers of the University of Groningen in the Netherlands split people with dementia into three groups. One group walked briskly four times a week for 30 minutes; a combination group walked twice a week and strength-trained twice a week for 30 minutes each; and a control group did no exercise.After nine weeks, Bossers put the participants through a battery of executive-function tests that measured problem-solving, inhibition and processing speed. He found that the combination group showed more improvement in executive function than the aerobic-only or control groups. “It seems that, for older adults, walking only is not enough. They need to do some strength training,” he says. “Lifting weights helps improve complex thoughts, problem-solving and multitasking”.
Immediate Attention Boost: These benefits extend to healthy adults too (not just those with MCI). In a year-long trial of healthy older women, Liu-Ambrose found that lifting weights, even just once a week, resulted in significant improvements in tests of executive function. Balancing and toning exercises, on the other hand, did not.
The combination of lifting weights and aerobic exercise might be particularly powerful because strength training triggers the release of a molecule called insulin-like growth factor-1 (IGF-1), a growth hormone produced in the liver that is known to affect communication between brain cells, and to promote the growth of new neurons and blood vessels. On the other hand, aerobic exercise mainly boosts BDNF, says Liu-Ambrose. In addition, Bossers says strength training also decreases levels of homocysteine, an inflammatory molecule that is increased in the brains of older adults with dementia. By combining aerobic exercise with strength training, you’re getting a more potent neurobiological cocktail. “You’re attacking the system in two ways,” he says.
The studies so far haven’t addressed how long the effects last, but preliminary findings suggest adults will have to keep exercising to maintain the benefits.
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