I workout five to six days a week -- cardio, weights, and stretching. My boyfriend rarely works out. Why is it that whenever we go for an all day hike or a long day of mountain biking, I end up sore for the next several days while he claims to feel fine? Is there some difference in body chemistry that could account for this, or is he just trying to sound tough?

— Jen Lyons, Watertown, Massachussets

Sounds to me like a suspicious case of excess male hormones trying to disguise some level of discomfort. Chances are, you’re both a little on the sore side after a big outing, and my guess would be that you’re fairing better than your partner is.

Still, you raise an important point. It comes as a surprise to many who religiously work out in the gym that they have trouble taking their fitness out the front door. Part of the problem can be explained by the relatively simple exercise physiology principle of specificity. Essentially, you've got to do what you're going to do to get fit to do it. This means that you need to hike or walk to get in shape for hiking, and ride a bike to get ready for a long ride.

Unfortunately, aerobics and many other health club fitness classes don’t have enough specificity to outdoor activities to prepare your body for the type of excursions you're taking. For aerobic training, consider walking or running on a treadmill instead of a step class. Use steep grades a couple of times a week, and mix that up with rides outside or on an exercise bike. Try to match your cardio sessions to the type of activities you like to do. If your rides and hikes are very hilly, you need to replicate that with your training.

Don’t get me wrong and assume that all the training you've been doing has been in vain -- you’re level of soreness would still be much worse coming straight from the couch, and you might not have had the fitness necessary to make the outing. The day after your next big outing, surprise your boyfriend by sitting on his lap suddenly or asking him to carry you down a flight of stairs. Watch carefully, his expression will tell you what he may not.