In the summer of 2010 I started a dieting and exercise regimen that resulted in my losing almost 25 pounds in 4 months. The exercise part of that regimen included a walk after work each day and 20 minutes on my elliptical trainer each morning.
Eventually I set an arbitrary goal of 200 calories burned in that 20 minute run--who doesn't like nice, round numbers?! After awhile I got to where I was burning 220-228 calories each morning. No, that isn't much, but it's better than not burning them. And the improvement in cardiovascular health was significant.
After 4 years I'd pretty much gained all that weight back, and now it's all back and then some. I haven't resumed the dieting or the afternoon walks, but when school started in August I started back on the elliptical trainer each morning. The first week of school I did 12 minutes a morning, the next week 13 minutes, etc., until I made it back to 20 minutes, and then I stayed at 20 minutes per morning. And, with the exception of only a handful of days last semester, I was on that elliptical trainer every "work morning". Being older and weighing more, though, I didn't get back to that magic 200 calories in 20 minutes.
Maybe it was having 2+ weeks off, I don't know, but at the end of the workout this morning the meter read 211 calories. So I'm still not back up to where I was, but for the first time this school year I passed that psychological barrier of 200.