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The Degrees of Freedom Problem

How does the body coordinate movement to perform a task? How is it that skilled performers can execute complex movements such as hitting or striking an object with consistent outcomes? Is it simply a matter of repetition after repetition of the movement in order to acquire the skill?

Nikolai Bernstein, a Soviet neurophysiologist, conducted experiments on expert blacksmiths to see how they coordinated their strikes. See image below:

Movement variability in coordinated strikes

What he realized is that every repetition of the movement was different, but the end result was the same. He referred to this as the degrees of freedom problem. The body has many options on how to organize itself to solve the goal of the movement. Novice level performers will typically “freeze the degrees of freedom” when they first begin to learn a new task. For example, when a beginner first jumps on a surfboard, they may first lock their joints in the lower half while they try to stay balanced on top of the board. Or when a novice golfer first learns to try and hit a golf ball, they may just use their arms and ignore the lower half all together. Over time they will learn to “unfreeze” these joints as the body becomes more “graceful” as the movement becomes more coordinated. However, as the image from one of Bernstein’s studies showed, even expert level performers have variations in the execution of their movement patterns. Yet, The result of the blacksmith hammer swings were very consistent in their strikes.

Bernstein coined the phrase, “Repetition Without Repetition”. Bernstein states the

“ processes of practice … consists in the gradual success of a search for optimal motor solutions to the appropriate problems. Because of this, practice, when properly undertaken, does not consist in repeating the means of solution of a motor problem time after time, but in the process of solving this problem again and again by techniques which we changed and perfected from repetition to repetition.”

(N. Bernstein, 1967, The Co-ordination and Regulation of Movements)

In our next blog, we will identify practice conditions that promote movement problem solving.

-Hunter Hoy


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