How a ballerina spins, as a neurophysical phenomenon.

The journal Human Movement Science carries research from Swiss sports scientists who have used ballet dancers to figure out how it can be possible for a human being to keep spinning on one leg without keeling over. The key is in keeping a visual reference point:

In dance, performing multiple rotations around the longitudinal axis is a complex task that can only be accomplished proficiently by highly skilled dancers. However, this extraordinary skill has been investigated sparsely. The few studies to date have focused on the biomechanical analysis of ballet rotations. However, none have investigated the influence of visual information on continuous rotations, such as Fouettés or à la Seconde turns. Therefore, the present study aims to examine the role of a visual reference on balance control and the dance-specific head coordination – spotting – during turning performance of highly skilled ballet dancers. To this end, 12 participants performed 12 Fouettés (females) or à la Seconde turns (males) with and without a visual reference. As dependent measures, we analysed balance control (i.e., supporting foot path length), spotting duration, head isolation, and orientation (i.e., deviation of pelvis from the front). A linear mixed model was performed to analyse the influence of the visual conditions overall and over the continued performance of 12 consecutive rotations. The results revealed that overall, path length was significantly smaller in the condition without a visual reference. Spotting duration and head isolation did not differ significantly between conditions. Moreover, dancers oriented themselves better towards the front in the condition with a visual reference. When looking closer into the progression of performance over each consecutive rotation, highly skilled ballet dancers significantly decreased the supporting foot path length, and improved orientation when turning with a visual reference. On the other hand, without a visual reference, the dancers increased the spotting duration over time. Additionally, dancers increased head isolation towards the end of the turns in both conditions. These findings suggest that a visual reference helps ballet dancers sustain performance of consecutive rotations, mainly in optimising balance control and orientation. Thus, the more rotations a ballet dancer must turn, the more relevant a visual reference becomes for sustaining successful performance.

Is it weird that I automatically start thinking of this research in terms of military applications? I lived with a hardcore ballet dancer for years; I know they’re basically commandos in tights.

[via Forbes]