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Rob Foster鈥檚 hands are full.

The 34-year-old CU Boulder senior is听married with four children, all daughters.听He鈥檚 loaded up on physiology, biomechanics听and anthropology courses and听knee-deep in medical school applications.听

He鈥檚 also leading a small research team听in the development of a bicycle for a potentially听vast ridership 鈥� obese people听of up to 450 pounds.听

Foster (IntPhys鈥�16) used to be听one of them.听

鈥淚 have a lot of empathy for people听who are in that position,鈥� the now-slender听former banker said in a spring听interview at the Locomotion Lab in the听Clare Small Arts & Sciences building.听

Hard at work for more than a year听now, Foster鈥檚 team aims to produce a final听prototype by the end of 2016 and make听the design publicly available at no charge.听

鈥淭ake it. Apply it. Use it,鈥� he said,听emphasizing that the group has no听commercial intentions. 鈥淗elp some folks drop some pounds.鈥澨�

Foster, 5鈥�11鈥�, knows the burdens of obesity.听Four years ago he weighed 327 pounds.听

鈥淢y earliest memories are of being听picked on,鈥� he said.听

But in early 2012 Foster and his wife,听Jessica, decided to slim down. They鈥檇听seen obesity鈥檚 toll on others, and their听weight was keeping them from fully听enjoying life with their girls, including听twins Autumn and Abigail, now 9.听

鈥淲e couldn鈥檛 go out to the playground,鈥澨齢e said.听

Jessica did Zumba; Foster took up听tennis, then started jogging and cycling.听

Using Google Scholar, Foster, then听working as a bank manager, dug into the听academic literature about obesity, looking听for guidance and understanding. He and听Jessica set what felt like reasonable goals听(lose two pounds a week) and let themselves听continue eating foods they liked,听but at far smaller portions. Their success听landed them on Good Morning, America.听

Today Foster is a trim 172 pounds.听He wears eyeglasses with rectangular听lenses, a close-cropped, neatly trimmed听beard and often a baseball cap. He鈥檚听finished two marathons and the听BolderBOULDER 10K three times.听He gets around town on an off-the rack听Fuji. You鈥檇 never know he听was once seriously overweight.听

But millions of Americans are听鈥� about 80 million, according to听the Centers for Disease Control,听or 35 percent of the adult population.听Foster wants to improve听the odds they鈥檒l slim down, and听he and his academic adviser,听Rodger Kram, think a customized听bicycle could help.听

鈥淔or very heavy people, even听walking, let alone jogging, imparts听high forces on the hip, knee and ankle听joints,鈥� said Kram, a CU integrative听physiology professor. 鈥淪wimming is another听form of aerobic exercise, but many听people are not comfortable wearing听bathing suits in public. Bicycling is a fun,听social and low-impact way to get aerobic听exercise and hence burn calories.鈥澨�

Foster grew up in Westminster, Colo.,听a strong high school student keen听on science. He briefly attended the听University of Northern Colorado, but听dropped out. He married, had kids and听spent nearly a decade in retail banking.听Occasionally he rued quitting school;听he鈥檇 seen himself as a medical doctor.听

Emboldened by his successful weight听loss and encouraged by Jessica, Foster听decided in 2012 that it wasn鈥檛 too late.听A year later he enrolled at CU and听dove headfirst into the study of integrative听physiology.听

Last fall he approached Kram about听doing original research. Kram suggested听the bike project, attempted once before听and suspended after a previous team听failed to connect with obese people.听After hearing Foster鈥檚 story, Kram听knew he鈥檇 found the right guy.听

鈥溾�榊ou have what we would call 鈥榦bese听experience,鈥欌�� Foster recalled Kram saying.听

Take it. Use it. Apply it. Help some folks lose some pounds.听

So Foster and a fellow undergraduate,听an engineer, began working on a bike听that鈥檚 more comfortable and safer for听the obese than off-the-rack bikes, seeking听input from heavy riders, including a听Boston blogger who writes as 鈥淭he听Fat Cyclist.鈥� The team is developing听a bike obese people could ride on Boulder鈥檚 bike paths, uphill or down, at听greater than walking speed.听

Bicycle manufacturers听have听previously produced听bikes for heavy riders,听but Foster has found听them lacking, especially听when it comes to the听braking systems, which听he called 鈥渋n no way adequate.鈥澨�

After testing all available types of听bike braking systems, the researchers听found the best ones required at least 43听feet and 4 seconds to stop a 450-pound听person traveling at 15 mph. The team听wants brakes that stop the same rider in听1.5 seconds and no more than 15 feet, in听line with existing federal standards for a听170-pound person.听

The researchers are not trying to听reinvent the bicycle 鈥� they鈥檙e trying听to adapt it, mainly by identifying an听optimal combination and configuration听of existing parts. The bike will听look more or less like regular bicycles,听an important point for obese people听they interviewed.听

鈥淭hey didn鈥檛 want anything that was听goofy looking,鈥� Foster said. 鈥淭hey don鈥檛听want to be the bear on a bicycle.鈥澨�

Beyond the brakes, the team is rethinking听the wheels and gears, seat post听(solid rather than hollow), 听aspects of听frame design (optimal height for the top听horizontal crossbar and handlebars) and听saddle (a tractor-style seat, perhaps).听

The braking system will be the most听complex new element, and听the challenge is to generate听greater braking force without听warping any parts.听The tentative solution听calls for a hydraulic听system with two front rotors听(as in a motorcycle)听and two sets of calipers,听effectively doubling the听friction on the front tire听when the brakes are applied.听It also calls for doubling the force听applied to the rear wheel.听

By spring Foster and team had produced听an initial prototype and were raising money听through a CU-sponsored to finish the project.听

Ultimately they want a bike that appeals听to obese riders 鈥� but still requires听them to work.

鈥淚f it鈥檚 too easy,鈥� said Foster, 鈥渨e鈥檙e听defeating our purpose.鈥澨�

Photo by Patrick Campbell听