"It means with running that we spend 2/3 of our energy to abuse our skeletons," he tells WebMD. "Only 1/3 is absorbed by the muscles. The muscles and the skeleton in biomechanics work like parallel systems. What the muscles can't take the skeleton does."
With the Exerlopers, Lekhtman says, the muscles do more of the work, burning three times the number of calories in the process. A pair of Exerlopers goes for $159.
Years ago, runners relied on stopwatches and car odometers to assess performance. But that has all changed, thanks to computers. The FS1 Speedometer, manufactured by FitSense Technology of Wellesley, Mass., sits in a lightweight pod secured between running shoe laces. It picks up speed, pace, distance, and calorie data and transmits them wirelessly up to a wristwatch.
It costs $180, says company spokesperson Ted Fitzpatrick, and for an extra $59, runners can uplink the watch to the FitSense web site to, for example, keep track of their progress.
"People want a higher level of feedback, more accurate information, and information available while doing the activity," Fitzpatrick says. "People want feedback that is positive, that compels them to work out more. When people out there see the numbers build, it becomes very powerful."
Past attempts at this kind of motivation -- the use of hip-worn pedometers in the late 1970s -- didn't work so well.
"Most pedometers sat on the hips. It assumed a fixed stride length, so it lost much accuracy," Fitzpatrick says. "The new idea is not to get a fixed stride length but the movement of the foot. Our rate of accuracy is 98%."
Runners content with logging their information after running have numerous computerized choices -- from software to internet sites. Many carry obvious names: Log-A-Jog, Runner's Log, i-run.com. By entering a minimal amount of information, runners can come up with some of the same data available on more expensive speedometers -- and more, such as visual representations of favorite running routes.
"One of the benefits is graphing," says Tim Meehle of VCR Incorporated, in Indiatlantic, Fla., which markets the Log-A-Jog. "In a logbook you might have one page [to write]. With electronic logging you can track your progress as part of a graph. Doing that in a logbook would be difficult."