When I go on a trip, my goal is to travel light to avoid lost luggage and quick transfers from airport to a hotel or home. I use a backpack and an over the shoulder bag. Last week these were stuffed to the gills with my computer, slides, transparencies, workout clothes, sundries and an alternative blouse for the traveling garb that can be spruced up to become a lecturing outfit.

This tightly packed ensemble is heavy. It's often the source of my on-the-road exercise as I lug it through airports avoiding moving sidewalks, trains between concourses and escalators. This workout often sends a message from my back that perhaps I overdid it. This week was no exception and brought to mind a few of the guidelines I use to assure I can continue this lifestyle habit. I've checked these out with my friendly physical therapist and pass them on for your use:

• Buy a backpack and shoulder back with padded straps for the best comfort you deserve.
• When you use a backpack, wear both shoulder straps. Lugging the pack around using only one strap can cause a shift of weight to one side leading to neck and muscle spasms and low-back pain. (I learned the hard way.)
• Adjust the straps on the pack to fit YOUR body. Too loose, and the backpack dangles uncomfortably causing spinal misalignment. Too tight and you'll cramp from constrictive movement. Each guarantees pain.
• Use a backpack with individualized compartments to position the contents more effectively, making sure pointy or bulky objects are packed away from the area that rests on your back.
• My friendly physical therapist says that, ideally, a backpack should weigh no more than 10% of body weight. A heavy backpack, if your back is not trained to support it, will cause you to bend forward in an attempt to support the weight on your back instead of your shoulders.

Thanks to weight training, I've carried much more than 10% of my weight without any trouble, but max out using a "backpacking" formula I learned years ago from Covert Bailey. Bailey's formula requires you know your body composition (percent body fat) so you can compute your pounds of fat and pounds of (non fat) lean mass. Once you do, subtract your fat weight from your lean mass weight. Divide the result in half to learn the limiting weight for your backpack.

For example, my lean mass is 118 pounds. I have 40 pounds (too much) of fat. 118-40 = 68 pounds. One half of that is 34 pounds--about twice what the physical therapist recommends. My gear sometimes feels that heavy but I max out at about 25 pounds. Keeping my pack light is a metaphor for my life. I'm hoping, in time, I'll be a minimalist.

P. S. If you use the above formula, be sure to start packing with a smaller weight and build to that max amount. You're guaranteed to also build strong legs and a tight derriere--especially if you use stairs instead of the escalator!!