Physical exercise is good for you, and so is mental exercise. But what happens when you mix the two?
Researchers at Queen's University are exploring a novel hypothesis about the potent synergies that result from performing physical and cognitive training sessions back-to-back. Preliminary evidence suggests that this one-two punch delivers a greater dose of brain-enhancing chemicals than doing the same exercises at different times of day, lending new support to the old idea that a healthy mind and a healthy body go hand-in-hand.
There's already plenty of evidence that physical exercise, on its own, boosts brain function, with both immediate and long-term effects. Exercise boosts levels of a group of a molecules known as brain-growth factors, in particular one called "brain-derived neurotrophic factor" (BDNF), which circulate in the blood and make the brain more responsive to learning and adaptation.
The evidence for cognitive training is more mixed. There's no doubt that, say, doing crossword puzzles or playing brain-training computer games will make you better at those specific tasks, but researchers are still debating to what extent the benefits are transferrable to other areas of day-to-day life.
Still, there is one effect of cognitive training that isn't in question: The act of thinking causes your brain to consume more oxygen, which draws more blood to the areas of the brain you're using. That effect gave Jeremy Walsh, a graduate student in the School of Kinesiology and Health Studies at Queen's, and his supervisor, Dr. Michael Tschakovsky, an idea.
"It's a very simple concept," Tschakovsky explains. "You'll get a greater effect on your brain if you can deliver a higher dose of brain-growth factors."
By starting with physical exercise, they reasoned, you first ramp up the concentration of growth factors circulating in your blood. Then following up immediately with cognitive training draws this growth-factor-rich blood to your brain. The result, over time, should be enhanced learning, and a greater proliferation and strengthening of connections between brain cells.
So far, much of the best evidence for combining physical and mental training has come from animal studies. Researchers at Rutgers University, for example, have shown that in rodents, physical activity dramatically ramps up the number of new brain cells produced, while cognitive training increases the number of these new brain cells that survive.
In humans, a major randomized trial is under way in Australia. Testing combined mental and physical training on older adults at risk of cognitive decline. Headed by Dr. Nicola Gates of the University of New South Wales, the Study of Mental Activity and Regular Training (SMART) will compare combined training with physical-only and mental-only training to see if the combination is better than the sum of the two individual parts.
Since levels of BDNF and other brain-growth factors decline with age, this form of training may be increasingly important as you get older. "The emerging idea is that a lifestyle of cognitive stimulation and physical activity is required starting in your 40s," Gates says.
Walsh, meanwhile, presented results from a pilot study at the Canadian Society for Exercise Physiology's annual meeting last fall. A group of 12 men and women between 60 and 77 years old performed a series of squats and leg presses three times a week for eight weeks, followed immediately by training sessions using commercial brain-training software from San Francisco company PositScience.
The results were highly encouraging – significant improvements in strength plus a host of cognitive measures such as selective attention, reaction time, and short- and long-term memory recall – and just as importantly, well received by the participants.
"The cognitive training tasks are hard, and at first some people found them frustrating," Walsh says. "But the program provides regular feedback, showing that everyone was improving. By the end, they loved it."
Walsh and Tschakovsky now plan to optimize the protocol by studying the mechanisms that enable the brain to respond to different types of physical and cognitive training, using MRI and other brain imaging tools.
One key question is how long the window for enhanced benefits stays open after you finish exercising. Walsh has found that BDNF levels increase immediately after a bout of lower-body resistance exercise, but begin declining again within about 10 minutes. However, there's some evidence that the brain remains in a state of heightened sensitivity for 30 to 60 minutes, he says.
So is this approach ready for prime time? Strictly speaking, the evidence isn't quite there yet. But for those interested in experimenting, it's a win-win proposition. Even if it turns out that combining physical and mental training is no better than doing them separately, you'll still come out way ahead compared with not doing them at all.
What types of physical and cognitive training combine best?
Aerobic exercise seems to have the biggest effect on the brain, says Queen's graduate student Jeremy Walsh. But research at the University of British Columbia and elsewhere has shown that resistance training also works – and this form of exercise may be more accessible to the older populations who are most in need of interventions to fight cognitive decline. For this reason, Walsh uses resistance training in his research.
Commercial brain-training products abound, and some, such as the program from PositScience that Walsh's studies use, offer specific research-tested benefits in the different brain functions they target. Still, the general idea can be extended to all sorts of cognitive stimuli, from children's classroom learning after playing at recess, to the social stimulus of a game of bridge with friends.
Alex Hutchinson blogs about exercise research at sweatscience.runnersworld.com.