QUESTION: I ran my first marathon last summer, and not successfully. I thought I'd prepared well, but I literally collapsed after 20 miles. What should I check on as the reason? What happened? - P.K.

ANSWER: A number of causes have to be explored for your collapse. It could have been from simple dehydration. Was the weather warm? Were you careful to continue drinking during the run? Was your body temperature quite high? These facts might have been assessed at the time of your collapse.Another possibility is inadequate preparation. I don't have details about your pre-marathon conditioning program. A mistake often made is trying to go too far without a buildup of one's endurance base.

Thirdly, you may have quite simply run out of fuel. The body has enough stored sugar to keep going for 2 to 4 hours. When the sugar tank empties, your body turns to fat energy. But the brain can't use fat to carry on nerve transmission. It rebels and you collapse.

If fuel supply is the problem, you will have to adjust your program. Load up with carbohydrates before the race and drink carbohydrate solutions during it. Those solutions should be a 5 percent to 10 percent concentration of carbohydrate polymer. It sounds like an esoteric product, but it isn't, really, and people at any sporting goods or health food store will know what you mean. They may even have pamphlets for marathon conditioning guides.

QUESTION: I have rheumatoid arthritis. I don't exercise because of it. The point is that I don't have arthritis really bad, and I think I have been using it as an excuse to become a couch potato. I am appalled at how little I can walk or exercise now. Can I safely exercise now, even with the rheumatoid arthritis? - N.F.

ANSWER: Most people with rheumatoid arthritis can exercise. But please get some advice from your doctor first. The intensity and type of exercise will depend on which joints are involved and how bad the joint inflammation is.

You make a good point for others to consider. Many arthritics are in poor condition because they have been fearful of damaging their joints further with exercise. However, most can get into an exercise program and feel stronger as a result. Water exercise (and there are some good water exercises) removes a lot of the weightbearing pressures. Even biking, properly guided, can be a generally safe activity for an arthritic.