BYU Engineers Develop "Y-Flex" Fitness Machine

  Built by Brigham Young University engineers, the prototype home fitness machine sports two rows of adjustable, bendable fiberglass poles with guides that simulate the feel of free-weights. The pole-guide systems are "compliant mechanisms," a special class of devices that transfer motion, force or energy without the use of movable joints à la fingernail clippers, backpack latches and paperclips. 

Playfully dubbed the Y-Flex, the machine has patent-pending technology that provides a weight-stack-free workout that feels more like weights than other resistance-based workout machines do, say engineering professors Larry Howell and Spencer Magleby. 

"The advantage to using compliant mechanisms in the machine is that it will cost less and be simpler for a manufacturer to make and assemble," says Howell, who literally wrote the book on compliant mechanisms as well as more than 100 scholarly papers on the topic. "Using the technology to reduce the number of joints also increases performance – the machine is more precise and reliable and there is reduced wear, weight and maintenance involved." 

The Y-Flex resembles other freestanding weight machines common to gyms, garages and basements – a bench connected to a tower with a cord and pulley system that allows users to select amounts of "weight" and pull or push that weight using a bar or handle. Instead of actual weights, the Y-Flex uses resistance, similar to what happens with fitness machines like Nautilus' Bowflex, which makes it light and easy to move. 

"The biggest difference between those machines and the Y-Flex is that they provide resistance like an uncoiled spring does – at first it's easy to push, and then it gets harder at the end when the coil is compressed," says Howell. "The compliant mechanism technology incorporated into the Y-Flex simulates the feel of constant weight from the start of an exercise to its end. It's more like what you experience with free-weights." 

Howell, Magleby and numerous mechanical engineering students have also incorporated compliant mechanisms into other devices like bicycle brakes and clutches on lawnmowers and chainsaws. 

More on this unique effort can be found at BYU Y-Flex News Release.

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