When talking about movement, degrees of freedom refers to the range of possible movements in our body. Essentially, there are lots of degrees of freedom!

When learning a new movement, we will typically move through phases. Initially the movement will look very rigid and uncoordinated. This is because we “freeze the degrees of freedom” – in other words, we do not let certain movements experience the full range of motion. Eventually, with practice, we begin to unfreeze the degrees of freedom and the movement starts to look more coordinated.

Freezing degrees of freedom during early learning is often associated with the conscious control of movements. However, this had not been tested until recently.

The study

Wouter van Ginneken and colleagues asked 40 participants to perform a throwing task. Participants were randomly assigned to either an error-strewn practice group or an error reduced  practice group.

The error-strewn group practiced throwing to a small target as this heightened the number of errors accumulated. Practicing with a high number of errors is associated with consciously controlling movements (as the performer tends to consciously correct errors). Comparatively, the error reduced group practiced throwing to a large target, which gradually reduced in size with practice. This group was not expected to consciously control their movements.

All participants performed 300 practice trials. On the following day, participants were  required to perform the task again to assess learning. Participants were also asked to perform the task under a variety of conditions, including when pressure was heightened. These additional tests were designed to encourage or discourage the conscious control of movements.

To measure “freezing degrees of freedom”, movement variability of the throwing arm was assessed. Greater “freezing” was assumed when movement variability was low (e.g., think of a rigid movement).

Finally, participants completed the movement specific reinvestment scale (MSRS). This is a questionnaire that measures a person’s tendency to consciously control their movements (NOTE: in sport, we often talk about these individuals as those who tend to overthink their movements).

Results

The key results were:

• During practice, scores on the MSRS were negatively associated with movement variability in the error-strewn group. This means that when errors were high, participants who had a tendency to consciously control their movements also tended to freeze their of degrees of freedom..
• During a delayed retention test, participants in the error-strewn group displayed less movement variability than participants in the error-reduced group. This means that most participants tended to freeze their degrees of freedom following practice that featured a high number of errors.
• When participants were asked to perform under pressure on day 2, movement variability was lower compared to when performing under no pressure. This occurred for both groups. Pressure is thought to heighten conscious control of movements; hence, this further demonstrates that the conscious control of movements is associated with freezing degrees of freedom.

Concluding message

The conscious control of movements appears to be associated with freezing degrees of freedom. In this study, participants who experienced more errors during during practice tended to consciously control their movements.

When teaching new skills, coaches should be aware of the impact of introducing tasks that are too difficult (hence, leading to a high number of errors), especially if the aim is for the learner to develop a free-flowing movement.

Reference

van Ginneken, W. F., Poolton, J. M., Capio, C. M., van der Kamp, J., Choi, C. S., & Masters, R. S. (2017). Conscious Control Is Associated With Freezing of Mechanical Degrees of Freedom During Motor Learning. Journal of Motor Behavior, 1-21.