“The present study suggests that simple exercise is better than cognitively demanding exercise during working hours,” lead author Keita Kamijo, an assistant professor on the faculty of sports sciences, Waseda University, Tokyo, told Reuters Health by email.
Kamijo and coauthor Ryuji Abe enrolled 28 men and had them perform tasks that challenge what’s known as working memory. Working memory is what allows people to maintain and update information in their brains about things they’re working on, such as assignments, goals, and strategies.
The men took the working-memory challenges before, immediately after, and 30 minutes after three different test periods on three different days. The test periods were assigned in random order and lasted 25 minutes each. In one, the men simply exercised on a stationary bike. In another, they performed a cognitive task while sitting on the bike, but they didn’t exercise. And in the third, they did both at the same time: they exercised on the bike and performed a cognitive task.
Studies have shown that aerobic exercise has a rapid beneficial effect on people’s ability to plan, pay attention, remember, and juggle tasks. The researchers expected, therefore, to see improvements in accuracy and reaction times on the working memory challenge after both periods in which the men exercised on the bike, Kamijo said.
The positive effects of the exercise-only intervention became evident 30 minutes after cycling.
But the exercise-cognition intervention resulted in “cognitive fatigue,” the investigators reported in the journal, Medicine & Science in Sport & Exercise.
Kamijo said the effects of acute exercise on cognitive function shouldn’t greatly differ between the sexes.
Dr. John Ratey, an associate clinical professor of psychiatry at Harvard Medical School in Boston, told Reuters Health by phone: “We’ve known for some time that exercise improves working memory. … The big take away here is that too much exercise may exhaust your brain for the next little while.”
To improve your memory and attention span in the short term at work or school, it’s best to do exercise not complicated by other demands, said Ratey, who was not involved in the research.
Tai chi, yoga, or high-intensity intervals that make your heart rate soar are examples of cognitively challenging exercises that may overwhelm the brain at first, said Ratey.
For long-term cognition, however, those kinds of exercises are healthy, too. “It is possible that a greater amount of load on the brain is required for chronic improvements in cognitive function, as with the overload principle of strength training,” Kamijo said.
Ratey said, “A good 80 to 90 percent of people will get more aroused, less tired, have more energy and be more motivated if they make a habit of exercise. The more involved with others and challenges they bring to themselves, the better they’ll build the brain up over time and improve their memory, attention span and their ability to deal with stress.”
By Cheryl Platzman Weinstock