Sass in Arlington: I am training for a 5K (my first, yay!) and can pretty easily run three miles on the treadmill. But it's a totally different story when I run outside. Why do I get so much more tired running outside on a relatively flat trail?

Howard Schneider: A couple of things to consider:

1) Wind resistance. Why do all those bike riders line up behind each other? To make the guy in front do all the work. There's no wind to push through on the treadmill.

2) There is flat and flat. Are you using an altimeter?

3) How are you pacing yourself? Are you trying to finish the three on the road in the same time you finish it on the treadmill? If so, that will take some time. It is harder to move yourself forward than to keep pace with the machine. To help build up, try setting the incline up a degree or so and increasing the speed.

D.C.: I'm interested in getting a personal trainer. Do you (or the chatters) have any experience with using personal training services like FIT or Body Smith?

Vicky Hallett: I've been to fabulous classes at both. FIT is definitely on the smaller side, but good trainers like Mike Everts don't need that much space to make you hurt. I speak from experience.