Reply #9: Getting used to is not such a bad thing [View All]

[dsewell]

There's partial truth to your first sentence. As you continue to do a particular activity, you become more efficient at doing the precise same amount of activity. This is particularly obvious with something like swimming, where the amount of energy an experienced swimmer will expend going a certain distance at a certain speed is much less than what a poor swimmer will expend (because of all the wasted movement). However, the more efficient you become at an activity, the easier it is to increase your speed; and the more fit you are, the easier it is to increase the intensity of workouts. So what's going to happen is eventually you'll hit a plateau where you're burning roughly the same amount of calories each time you do your half-hour workout, but you're not going to start burning fewer calories after that point (relative to body weight, anyway).

Increasing intensity is good for burning calories. As is varying your workout by including sprint intervals (whatever counts as a "sprint" in your workout) of 90 seconds or so followed by 90 seconds of relative rest.

I've also heard that fat-burning really kicks in once you've been doing aerobic activity continuously for 45 minutes, but I don't know if that's really a magic number. It's definitely the case that weight loss is easier if you have the time to spend an hour rather than a half hour a day at aerobic activity.