You've run out of gorp, your water bottle's empty and your wheels are hitting more tree roots than they're missing. And you've got five miles left to go.

It's amazing what the thought of a hot shower and a soft bed can do for the morale at times like this. If a good night's sleep is more important to you than the wonders of nature, forget the sleeping bag and pots and pans. By staying in youth hostels and splurging on a motel once or twice, you can bike the C&O Canal without having to carry much more than a toothbrush.

American Youth Hostels, Inc., a non-profit, recreational and educational organization founded in 1934, runs three hostels along the towpath's route. They're not exactly the height of luxury, but they have what courts: beds and showers. And the price is right - usually about $2 to $3 a night. Most have cooking facilities and utensils, which means you can buy your food as you go along, at neighborhood groceries.

The hostels are located at approximately the 175-, 100-, and 60-mile marks. So if you're making the trip on a three-day week-end, traveling 50-60 miles a day (about the limit the human body can take, given the tree roots), you can sleep in hostels the first and last nights and treat yourself to a motel the middle night. Three days is about right for a non-camping trip. If you take six days, traveling about 30 miles a day, that leaves three hostel-less nights, and the motel prices will get to be expensive.

All you need to stay at the hostels are an AYH membership card and a "sleep sack" - a sort of gauzy body bag which AYH requires to keep the beds clean. You can buy one from them for $7.50, or make it yourself out of an old sheet (the membership manual has instructions). It's a good idea to make reservations for all the places listed below, especially during the summer months.

Annual AYH dues are $11 for adults over 18, $5 for children, or $12 for a family. There's also a $2 introductory pass you can use at a hostel on a one-time trial basis (the $2 applies toward the cost of the yearly pass). To join, stop in at the Potomac Area Council, 1520 16th St. NW, or call 462-5780.