Get your heart pumping in the fight against forgetfulness

Regular exercise releases brain chemicals that support better memory, concentration, and mental sharpness.

Do you sometimes feel a little foggy? Or frustrated with frequent bouts of forgetfulness? Here's some good news from the frontiers of brain-body science:

"There's a lot you can do to prevent cognitive decline, or slow it down, or to recover memory function that you might feel you have lost," says Dr. John Ratey, associate clinical professor of psychiatry at Harvard Medical School and author of Spark: The Revolutionary New Science of Exercise and the Brain�(2008). The secret? Regular exercise.

How exercise helps the brain

Regular, moderately intense exercise maintains healthy blood pressure and weight, helps you feel more energetic, lifts your mood, lowers stress and anxiety, and keeps your heart healthy. Raising your heartbeat sends blood and oxygen to the brain, but other changes happen, too. A lot of research suggests that exercising moderately and regularly stimulates brain regions involved in memory function to release a chemical called brain-derived neurotrophic factor (BDNF).

BDNF rewires memory circuits so they work better. "When you exercise and move around, you are using more brain cells," Dr. Ratey says. "Using more brain cells turns on the genes to make
more BDNF.

"My older patients do say they feel sharper," Dr. Ratey says. "They feel that they're remembering things better. I do think there is evidence for that."

How much exercise?

You can't buy BDNF in a jar; only the brain can make it for you. And exercising regularly is required. That means 30 minutes of moderate-intensity exercise, ideally five days a week.

The threshold for brain benefit seems to be raising your heart rate to 70% of maximum. For men, maximum heart rate is roughly 220 minus your age; then take 70% of that. For a 70-year-old man, the target heart rate during exercise would thus be 105 beats per minute. This assumes your physician has cleared you for that level of exercise; always talk to a doctor before starting a new exercise program.

Moderate-intensity exercise includes brisk walking and swimming as well as anything else that gets your blood moving, including yard or housework. "Getting your heart rate up is something you can do just by walking fast," Dr. Ratey says. "You don't have to be running."

And now, a reality check: Exercising once or twice a week is just not going to do it. "It's probably good for your body," Dr. Ratey says, "but it won't get you there in terms of the cognitive benefits. You also have to continue to do it to continue accruing the benefits."

Finally, to achieve overall and sustained fitness with aging, Dr. Ratey says, it's important to also include exercises to maintain balance skills—like resistance exercise to strengthen and steady your legs. Also essential: core exercise for your lower back and abdominals. "For anybody who really wants to remain healthy brain-wise and body-wise, you have to do all three."