By GRETCHEN REYNOLDS
Dr. Matthieu Boisgontier says that humans may have a predilection for being sedentary to conserve energy. (Ed Jones/Agence France-Presse — Getty Images).
Are we born to be physically lazy? A new neurological study suggests that we probably are. It finds that even when people know that exercise is desirable and plan to work out, certain electrical signals within their brains may be nudging them toward being sedentary.
The study’s authors hope that learning how our minds may undermine our exercise intentions could give us renewed motivation to move.
Exercise physiologists have long been flummoxed by the difference between people’s desires to be physically active and their actual behavior. Few of us exercise regularly, even though we know that it is important for health and well being.
Typically, we blame lack of time, facilities or ability. But recently an international group of researchers began to wonder whether part of the cause might lie deeper.
For an earlier review, these scientists had examined past research about exercise attitudes and behavior and found that people sincerely wished to be active. But few people followed through. So maybe, the scientists thought, something was going on inside their skulls that dampened their enthusiasm for exercise.
To find out, they recruited 29 healthy young men and women. All of the volunteers told the scientists that they wanted to be physically active, although only a few of them regularly were. The researchers fitted each with electrodes that recorded the brain’s electrical activity.
The volunteers then completed a computer test designed to probe how they felt about exercise. They were assigned an avatar, shaped like a stick figure. Their avatar, which they could control, could interact on the screen with other stick-figure images related to being active or inert. For instance, an image of a figure biking might pop up, followed almost instantly by a depiction of a figure reclining in a hammock.
The volunteers were told to move their avatars as rapidly as possible toward the active images and away from the sedentary ones, and then vice versa. This test is known as an “approach-avoidance task” and is thought to be an indicator of how people consciously feel about whatever is depicted on the screen.
The volunteers were almost uniformly quicker to move toward the active images than the sedentary ones and slower to avoid those same active stick figures. They all consciously preferred the figures that were in motion.
But at an unconscious level, their brains did not seem to agree. According to the readouts of electrical brain activity, the volunteers had to deploy far more brain resources to move toward physically active images than toward sedentary ones, especially in parts of the brain related to inhibiting actions.
Brain activity there was much slighter when people moved toward hammocks, suggesting that those images called to the brain more strongly than the images of cycling, whatever people told themselves consciously.
“To me, these findings would seem to indicate that our brains are innately attracted to being sedentary,” said Matthieu Boisgontier, a postdoctoral researcher at the University of British Columbia in Vancouver who led the study in conjunction with Boris Cheval at the University of Geneva in Switzerland.
The results make sense from an evolutionary standpoint, Dr. Boisgontier said. “Conserving energy was necessary” for us as a species in our early days, he said.
The lesson of the current experiment is helpful, Dr. Boisgontier said. People who are reluctant to exercise “should maybe know that it is not just them,” he said.
Humans may have a natural bias toward inactivity. But we also can consciously choose to move, Dr. Boisgontier said, despite what our brains may think.