Programmed for laziness

An exoskeleton was used to monitor energy use while walking. - Photo courtesy of SFU News

New research from SFU has demonstrated that the nervous system is continuously optimizing energy use, taking a ‘lazy’ approach in order to be more energy efficient.

SFU professor of biomedical physiology and kinesiology Max Donelan with his colleagues conducted experiments testing certain theories about how people learn how to move.

One theory they have generated is that the nervous system doesn’t move as accurately as it could. Instead, it is constantly monitoring movement and will often compromise accuracy in order to save energy.

Jessica Selinger, an SFU PhD candidate and lead author of the paper, described how the team tested this theory. Selinger’s research was published in Current Biology this month.

“We asked participants to wear a robotic exoskeleton that made certain abnormal ways of walking energetically easier than walking in a ‘normal’ way. They accomplished this by applying high energetic penalties to ‘normal’ ways of walking, and much smaller penalties to specific abnormal way of walking.”

The researchers found that soon after participants were exposed to the robotic exoskeleton, they changed the way they walked. They noted that the characteristics of walking are well-established in individuals, and that the speed at which participants changed the way they walked was very quick. They concluded that this indicates that the nervous system is constantly trying to optimize energy use.

Selinger spoke to the practical implications of her researcher: “The drive to continuously seek energetic optima presents challenges and opportunities for rehabilitating and augmenting human movement.”

She explained that rehabilitation of those who suffer from gait disorders (disordered walking) could, instead of focusing on restoring symmetric movement, focus on “reshaping underlying energetic landscapes” by using technology to make a symmetrical gait that is energy efficient.

Selinger added, “Our findings also have important implications for the recent and exciting push to design and build robotic exoskeletons to improve human performance.”

Selinger commented on whether the ‘laziness’ or energy efficiency of the nervous system could also apply to other characteristics such as thinking, talking, or decision making.

“We think that minimizing energetic cost is a principle that guides most of our movements. While it may play a particularly big role in walking, we suspect that the nervous system is always concerned about it, even for lower cost tasks like reaching or standing.”

Selinger hinted that the ability to optimize movements to reduce energy use may have been an important survival strategy.

While we live in a culture where calorie heavy foods are widely available, that certainly wasn’t the case for our prehistoric ancestors. She speculated that the nervous system’s goal of reducing energy expenditure may have helped stave off starvation.

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