Treadmills make you walk slower but work harder and feel worse

A bit of an unusual study from Brazil just published online in Medicine & Science in Sports & Exercise. Basically they asked 34 young adults to go for a 20-minute walk either on a treadmill or outdoors on a 400-metre track, at whatever pace they would “feel happy to do regularly.” The results: they chose to walk significantly faster on the track than on the treadmill — but their percent of VO2max and their perceived exertion was higher on the treadmill, despite the slower speed. In addition, their “affective valence was more positive” (i.e. they were happier) on the track.

The goal of the study was to figure how to convince more people to exercise (and in that sense, it was somewhat unsuccessful because the volunteers chose paces that were too slow to elicit significant fitness gains), and to figure out whether recommendations formulated in the lab can be applied to normal outdoor conditions.

Leaving aside the psychology (which is certainly interesting — I know I’m happier outside than on a treadmill!), the fact that people walked more slowly but worked harder on the treadmill is odd. This wasn’t a biomechanics study, but it seems like more ammunition for those who say that movement on a treadmill is fundamentally different from overground — a debate that’s been dragging on for a long time now. I still don’t really understand why it should be different (other than wind resistance, which wouldn’t explain the current results), but apparently this is one of those deep mysteries…