Juggling may sound like mere entertainment, but a study led by Johns Hopkins engineers has used this circus skill to gather critical clues about how vision and the sense of touch help control the way humans and animals move their limbs in a repetitive way, such as in running. The findings eventually may aid in the treatment of people with neurological diseases and could lead to prosthetic limbs and robots that move more efficiently.

The study was published online recently by the Journal of Neurophysiology and is the cover article in the journal’s March 2014 print edition.

In their paper, the team led by Johns Hopkins researchers detailed the unusual jump from juggling for fun to serious science. Jugglers, they explained, rely on repeated rhythmic motions to keep multiple balls aloft. Similar forms of rhythmic movement are also common in the animal world, where effective locomotion is equally important to a swift-moving gazelle and to the cheetah that’s chasing it.

“It turns out that the art of juggling provides an interesting window into many of the same questions that you try to answer when you study forms of locomotion, such as walking or running,” said Noah Cowan, an associate professor of mechanical engineering who supervised the research. “In our study, we had participants stand still and use their hands in a rhythmic way. It’s very much like watching them move their feet as they run. But we used juggling as a model for rhythmic motor coordination because it’s a simpler system to study.”

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