By Todd Hargrove


I'm an author, bodyworker and movement therapist. I write about coordination, pain, complexity, play, the nervous system, body/mind issues and more.

New Study on Efficiency: Mental and Physical

A new study sheds some interesting light on the concept of movement efficiency, which is something I write about a lot on this blog. The study suggests that the mental work required to perform a certain movement, like the physical work itself, can vary significantly depending on whether it is done with efficiency or not. Let's take a look. The study asked subjects to learn how to control movements of a cursor on a computer screen by manipulating a joystick and reaching with a robotic arm. While the participants performed the reaching movements, researchers collected data on arm muscle activation and overall energy expenditure.

Unsurprisingly, the subjects gained greater skill as they practiced, and this resulted in them using less muscular activity and less energy to perform the movements. The surprising thing is that the energy required to perform the movements continued to decline even after performance and muscular activity levels plateaued. One scientist remarked that "the results are very surprising and challenge the widely held assumption that muscle activity entirely explains changes in metabolic cost.” The study authors concluded that the continued decrease in the metabolic cost of the movement may be explained by greater efficiency in brain activity as opposed to muscle activity.

I think it is possible that there were muscular costs not accounted for in the data collection, which measured only muscular activity in the arms, and not in other muscles such as postural muscles which might have also learned to become more efficient in the task, and on a slower learning curve. However, I find the brain efficiency hypothesis to be very plausible in light of what we know from motor learning theory, which describes how learned movements move from the "cognitive" to the "automatic" stages of competence. And, more importantly, I find the whole idea to be very cool.

This would imply that even if two people are moving in a completely identical manner using the exact same muscle fibers to perform the exact same movements, one person might actually be using measurably less energy than the other, simply because his brain is working more efficiently to accomplish the same movements.

It also implies that even when you have completely peaked in terms of your performance of a particular skill, you still have room for improvement in reducing the amount of brain power it takes to perform the skill. This might be important in situations that require multitasking. For example, in soccer you may have to perform several skills at once, such as dribbling a ball while locating a teammate for a pass. So maybe you should continue to practice dribbling even if it never improves your actual dribbling, because it might still increase your mental reserves available to perform other activities while dribbling.

I am reminded that certain innovative trainers will challenge their athletes with purely mental tasks such as multiplication tables during the performance of sport specific skills. Perhaps they are finding ways of improving the mental efficiency of their athletes even if these drills do little for physical efficiency.

This also reminds me that the true virtuosos in any particular activity, whether that is music, sports or dance, are those  who have the ability to constantly practice fundamentals which they have already seemingly completely mastered. Perhaps they know that even if they are moving perfectly on the outside, there's always room for improvement on the inside.

Some Good Quotes from "Movement" by Gray Cook

The Arthrokinetic Reflex