The New York Times has an article about how some people use heart-rate monitors, GPS, and power-meters to quantify their exercise. And some of them obsess over the data . These people are not necessarily elite athletes like The Lance. They are active people, who just want to know exactly how many calories they burned or how many watts they can produce in a workout.
Doctors warn that this behavior can do more harm than good. Some people keep checking their heart rate monitor, and expect the rate to increase with each workout. Then they over-train and burn out.
Of course, the simplest training device is the lowly pedometer. Health experts suggest taking 10,000 steps each day as a way to get fit and lose weight. A friend of mine did this for an exercise study. Everyone wore pedometers and kept an activity log.
The researchers were surprised that one very overweight woman seemed not to be losing any weight, even though she walked 20,000 steps a day. After a couple of weeks, she finally confessed that she wasn’t really doing the distance. She would just hold the pedometer in her hand, and shake it for hours while watching her soaps.