My sister recently had some serious knee pain. She continued to run, and it got worse, until eventually it was terribly sore all of the time. She ignored my admonishments to take a break. Instead, she hopped on a bike or an elliptical.

Eventually, during the Ragnar Relay's Wasatch Back, her knee was so sore and swollen, she could barely finish the last leg of her race.

After a visit to the University of Utah's Orthopedic Center, she learned it was just irritated. Too much running on crummy shoes, and she has a harsh running style that she might need to change. She's going to have to do a couple of sessions of physical therapy, but all in all, it turned out better than I thought it would.

My sister and I talked about why she couldn't bring herself to take a break. The thing about exercise is that it becomes a tool in helping us deal with stress, disappointment and even trauma. It becomes a way to unwind, relax and let go of junk that serves no purpose other than to weigh us down.

I have actually gone out for a run in a near homicidal rage and returned feeling like I could extend forgiveness to just about anyone. Big, all-consuming problems seem to shrink in proportion to the miles I run. It is the same for my sister, maybe more so. She realized she was jeopardizing her ability to run long-term, but she just couldn't manage more than a day or two without the release that came with running. I told her that's why I took up yoga, swimming and even cycling. I read an article a few years ago that I feel is very true for me. It said that your latest run is only as good as your next rest. When I go out and run 10 or 12 miles, I have no trouble resting. I have no trouble finding another way to unwind. I journal, read a book, ride my horse or, my personal favorite, take a nap.

Being dependent on one particular type of exercise for mental health is, in some ways, almost as dangerous as not having an outlet. Our bodies are amazing, but they are not machines.

Pain can be a signal that workouts are making us stronger, but it can also be a warning that we need to slow down, maybe sit out a day. The hardest part is deciphering those signals. Unfortunately, our desires and competitive spirits make those signals even more difficult to read.

Next time you feel confused about the pain you feel, consider what's at stake. If you're reluctant to take a few days off, think about how you'll feel if your persistence leads to serious injury or permanent damage. Then instead of a few days or weeks off, you're looking at life-altering consequences.

And if that doesn't persuade you, consider that it could be a great time to try something new.

E-mail: adonaldson@desnews.com