A Personal Trainer, in the Palm of Your Hand

Nov. 16, 2007 -- A prototype technology could make lifting weights a lighter task.

Working out with free weights is an excellent way to build strength and burn off fat. But keeping track of the sets and reps can be tedious. It's easy to accidentally skip steps, miscount a sequence, or forget your progress.

The new technique uses sensor-embedded gloves and a waistband designed to recognize what type of exercise a person is doing and how many repetitions have been completed. Tied with an online community of exercisers, the system could lead to a new kind of digital personal trainer that gives real-time tips or warnings on form and posture and also connects people with others to help achieve their goals.

"People can use this to share their progress with others. They can share their secret and how they do their exercise," said Keng-hao Chang, a graduate student of computer science at the University of California, Berkeley.

Workout gloves are fixed with wireless sensors called accelerometers, which track motion in three directions: side to side, up and down, and front and back. The data collected is sent via a Bluetooth connection to a computer, where custom software analyzes the information to distinguish a bicep curl from a tricep curl. (Eventually the data could be sent to a mobile phone or PDA.)

Another accelerometer on the belt also track motions in three axes to distinguish whether the exerciser is standing or lying on a bench. That information is helpful because the motion of some exercises -- for example a bench press, which works the chest, and the movement of an overhead dumbbell press, which works the shoulders -- are quite similar.

In initial tests, the sensors were between 85 percent and 95 percent accurate in recognizing the exercise being performed. And out of 100 repetitions, the system miscounted by less than five.