Blog

Harvard Medical School Publications – Does exercise make you smarter?

Can exercise make us smarter?

We hear so much about the physical benefits of regular exercise. But what effects do exercise and staying fit have on our cognitive function? Research has looked at how well people perform mentally, both while exercising and immediately after an exercise session. Other research has examined the association between fitness level and age-related cognitive decline.

Unlike physical measurements that can be taken with some precision, defining tests of mental performance and exercise to get reliable outcomes is a much greater challenge. Despite the obstacles, researchers have made some headway.

Mental performance tasks influenced by exercise

During a session of moderately intense aerobic exercise, mental performance improves in several measurable ways:

reaction time

perception and interpretation of visual images

executive control processes

Of these, exercise exerts the most positive influence on tasks of executive control, such as:

planning

scheduling

coordination of people, places, events, etc.

working memory—the brain’s ability to temporarily store and manage the information required to carry out complex mental functions

inhibition—the ability to block out unnecessary distractions

How long does improvement take?

Improved cognitive function begins to show at about 20 minutes of moderate intensity aerobic exercise and will be maintained for about another 40 minutes. Beyond 60 minutes of exercise, fatigue is likely to become a factor. For very fit individuals, enhanced mental performance could continue beyond an hour.

Once fatigue sets in, you start to lose the mental edge you have gained. If exercise continues, then mental performance actually will decline to a level lower than where you started.

These positive cognitive effects of exercising for 20 to 60 minutes are primarily related to increase in blood flow to the brain and stimulation of nerve cells to release more neurotransmitters (chemicals that send signals between brain cells). These positive effects will be maintained for a short time after the exercise session as long as you have not become overly fatigued. If you expect to have a long and hard workout, don’t plan on doing any important decision making or complex mental functions immediately afterward.

Influence of exercise intensity

Moderate intensity aerobic exercise that keeps you breathing a little faster and makes you sweat is probably the optimal intensity level to get the mental boost. If you monitor your heart rate to guide your intensity level, you want to strive for about 75% of your maximal heart rate.

With moderate intensity exercise, your body is activating the sympathetic nervous system and raising levels of adrenalin. These are likely the two main factors driving improvements in mental performance.

At high intensity of exercise, you will perceive your level of exertion and this sensation will likely interfere with concentration and ability to perform mental tasks.

Fluid intake and exercise

Dehydration is associated with a marked reduction in mental performance, independent of whether it is exercise-induced or caused by other factors. Researchers have shown that the decreased cognitive function immediately after exercise-induced dehydration can be quickly reversed once fluids are given to return body weight to the pre-exercise level.

One study found that hyper-hydration, extra fluid beyond what is lost, improved mental performance more than just replacing fluid losses. This principle should not be taken to extreme since over-hydration with water during prolonged exercise can dangerously lower blood levels of sodium (a condition called hyponatremia).

Water and sports drinks are equally effective at maintaining hydration during exercise. Sports drinks that contain simple carbohydrates (sugar) may provide a mental advantage for other reasons.

Carbohydrates to feed the brain

The brain needs a constant supply of glucose to function normally. During exercise, the body preferentially uses glucose as the main energy source for contracting muscles, including the heart and the muscles used to expand the lungs. At moderate intensity exercise of 20 to 60 minutes, there is still plenty of sugar available to the brain to allow the improved mental performance noted above. If exercise is more prolonged, especially at a high intensity level, then the amount of blood sugar available to the brain may be an issue.

Studies have shown that cognitive function is better when fluids are replaced with a sugar-containing solution rather than a drink without any calories. However, when blood glucose levels are measured, they are not low enough to say that hypoglycemia is the explanation. More likely, the sugar-containing solutions improve endurance and lessen the perceived level of exertion. Improving both of these factors positively impacts mental performance.

Boosting cognition now and for the future

In the short run, each session of aerobic exercise on a stable piece of equipment such as a stationary bike, treadmill, or elliptical machine has the potential to give you a double benefit for your time spent. Not only will you be improving your fitness, your ability to concentrate on and perform mental tasks also will likely be enhanced.

In the long run, physical activity appears to be at least as important in staying mentally sharp as keeping your mind active and maintaining strong social connections. Multiple studies have shown that people who exercise regularly will have less age-related cognitive decline and lose less brain tissue, as seen on MRI and PET scans.

Making changes to create a healthful diet that you can enjoy!

Harvard Health Publications
 Tips for healthy eating:
Here are five tips to create a healthful diet that you can enjoy.

Learn to think about food in a new way. Years ago, meat and potatoes were the American ideal. Now we know that vegetables, fruits, whole grains, nuts, and fish are best.

Experiment with new recipes and meal plans. Be creative and take chances. Instead of dreading your new diet, have fun with it.

Change slowly. By the time you are 40, you’ll have eaten some 40,000 meals—and lots of snacks besides. Give yourself time to change, targeting one item a week.

Start with breakfast, switching from eggs, bacon, donuts, white toast, or bagels to oatmeal or bran cereal and fruit. If you just can’t spare 10 minutes for a sit-down breakfast, grab high-fiber cereal bars instead of donuts or muffins.

Next, try out salads, low-fat yogurt or low-fat cottage cheese, tuna or peanut butter sandwiches, and fruit for lunch.

Snack on unsalted nuts, trail mix, fruit, raw veggies, Rye Krisp, or graham crackers. Try eating a few handfuls of a crunchy fiber cereal such as Kashi, or nibble on a cereal bar.

For dinner, experiment with fish, skinless poultry, beans, brown rice, whole-wheat pasta, and, of course, salads and veggies.

Fruit and low-fat frozen desserts are examples of desirable after-dinner treats. And there’s nothing wrong with the occasional cake, pie, or chocolates as long as the portions are moderate.

Be relaxed about your diet. You will never find a perfect food. Not everything on your plate needs to have a higher purpose. Take your tastes and preferences into account. If roast beef is your favorite food, it is okay to eat it—but try to make it a Sunday treat instead of a daily staple. The choices are your—and the better your overall diet, the more “wiggle room” you’ll have to indulge your passions.

Take a long-range view. Don’t get down on yourself if you slip up or “cheat” from time to time. Don’t worry about every meal, much less every mouthful. Your nutritional peaks and valleys will balance out if your overall dietary pattern is sound.