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Depending on the high school, the average amount of time between classes is somewhere between three and five minutes. This gives students little time to make a trip to their locker to get the books they need without being late for class.

Usually, my backpack weighs about 20 pounds; that's about 18 percent of my own weight. This puts it three points over the recommended standard load of a pack, which should be between 10 and 15 percent of a person's weight.

Over half of the entire student population in the United States carries more than the recommended weight, and some exceed it by much higher numbers. This results in countless back injuries to teens. In 1998, National Public Radio reported that 65 percent of adolescents' visits to doctors were for backpack-related injuries.

However, recent studies indicate the biggest problem involved in backpack injuries is not weight, but, in fact, improper handling. Students often will carry their packs over one shoulder, rather than two like they should. Wearing a backpack this way places extreme pressure on one side of a person's body, forcing the spine to support an uneven amount of weight. Occasionally, students carry the pack by the top strap instead of wearing it. This not only throws off the balance of weight on the spine but can also lead to injuries in the arms or wrists.

Over the past few years, manufacturers like Sierra and Eastport have tried to take off some of the weight off, placing newer, more efficient products on the market. Rolling backpacks have steadily gained popularity, though they weigh more when empty than a regular pack and usually don't fit in most lockers. Some backpacks are designed with a single, wide strap that goes crosswise across the shoulder and chest; they're fashionable, but regular two-strap bags are generally more reliable for larger loads.

The most recent of these new packs is the triangular-shaped AirTec that is designed to help coordinate with the body's shape and movement. It also sports three straps, two of which are worn in the usual fashion over the shoulders, while the third goes across the lower chest to help even out the weight.

Before running out and buying one of these products, think about lightening up your own pack.

Most bags are filled with large items that can easily be done without, such as CD players, Rollerblades and water bottles. Simply sorting through your bag in the morning can be surprisingly effective in reducing weight. And it doesn't hurt to think ahead; doing homework in spare time between classes can mean not carrying a textbook home.

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