Logo: University of Southern California

Muscle Beach Slackline Turns Viterbi Biomedical Laboratory

Francisco Valero-Cuevas and collaborators from Harvard University probe the physiological hows of a balancing act
May 09, 2012 —

A new frontier for research at the Viterbi School’s Department of Biomedical Engineering is gymnastics. The laboratory is Muscle Beach in Santa Monica Beach, just south of the Santa Monica pier. There the agile and fit congregate daily, and where recently a collaboration between Professor Francisco Valero-Cuevas and Harvard colleagues Dr. Paolo Ciccarese and Prof. L. Mahadevan studied human agility with electronic sensors, video and laptop computers.

The experimental apparatus was a slackline, the tightrope’s looser cousin, 2-inch wide strong fabric ribbons strung between steel poles rigidly, but showing a pronounced sag when a person balances upon it, a challenging skill often seen in tents over sawdust.

Slack 2
Dr. Paolo Ciccarese, left, and Professor Franciso Valero-Cuevas in the lab.
Ciccarese and Valero-Cuevas hope that detailed study of the physics of the slacklines can illuminate body control and feedback mechanisms, and perhaps even shed light on the path by which ancestral primates learned to move smoothly and then stably on two legs.

The two met when Valero-Cuevas, a specialist in neuromuscular systems and biomechanics was in Cambridge giving a talk at Harvard University. He met with Professor Mahadevan and Ciccarese, a postdoctoral fellow of his. Ciccarese described his recently published work creating and solving dynamical equations describing slackline mechanics, which he was hoping to verify experimentally. His equations predicted the stability in two dimensions, vertical (the spring upwards of the wire) and horizontal (the side-to-side swaying.)

“If you want to try and test your theory on athletes,” said Valero-Cuevas, thinking of the community of slackline walkers that he had observed at Muscle Beach, “I know a place you can find them.”

Ciccarese then came for a visit to USC, where a group of grad students, post docs and specialist Emily Lawrence had discussed his needs and created equipment to meet them. Lawrence had formerly worked at the NASA Johnson Space Center in Houston quantifying astronaut performance.

Wearing wireless sensors, an athlete walks the slackline...
The equipment was assembled, and taken out to the beach — and the next step was to wait for walkers. Who appeared, as they do frequently at Santa Monica beach, which is the prime Los Angeles venue for amateur slackline walking. The steel poles available for slackline stringing are immediately adjacent to the landmark flying rings.

Many walkers, said Valero-Cuevas, were intrigued when they heard about the project, and readily agreed to cooperate. The first day, a French gymnast appeared, along with three Americans with the skill. The second day, the first candidate was a an Italian visitor on her first day in Los Angeles.

Valero-Cuevas and staff attached a set of five sensors to her torso, ankles and forearms, feeding data wirelessly into a laptop computer on the accelerations measured in real time, and another computer recording tension on the slackline. Valero-Cuevas and Ciccarese explained each step in fluent Italian.

Waiting in line to walk the line was a stocking-capped young American.

The next step is analysis, according to the scientists. “We have only just begun.” Valero-Cuevas emphasized.

A recent story on Science Now referencing a publication by Ciccarese and Mahadevan quotes Valero-Cuevas: "'High performance behaviors are more likely tied to evolutionary fitness, like jumping from rock to rock or maintaining balance on a branch." He adds that studying how people learn and perform complicated tasks reveals the strategies and limitations of the brain and the body in demanding physical situations. This can provide insight into impairment and rehabilitation, he says. 'What to us is very simple to do, like taking a step, to someone who has had a stroke can be just as challenging as learning to slackline.'"

Helping Valero-Cuevas, Ciccarese, Mahadevan and Lawrence are students from the Brain-Body Dynamics Lab who come from both the Biokinesiology and Biomedical Engineering graduate programs, including Brendan Holt (BME), Srideep Musuvathy (BME), Alexander Reyes, (BME), Wenhsin Hu (BME), Josh Inouye (BME), Na Hyeon (Hannah) Ko (BK), Sudarshan Dayanidhi (BK), John Rocamora (BME), Kornelus Racz (Neuroscience Graduate Program) and Manish Kurse (BME) along with visiting graduate student Richard Bumann from Switzerland.