Backpacks with super heroes, cool cartoon characters, and vibrant patterns and colors grab kids' attention on back-to-school shopping trips. For parents, buying a backpack is a decision that should be made with heavy consideration, or it could be killer on kids' backs.

The top criteria should be choosing a backpack that provides the correct fit and support to lessen the risk of muscle soreness, fatigue and low back pain that can last through adulthood, according to the American Occupational Therapy Association (AOTA). With about 79 million students across the U.S., backpacks have become such a serious concern that the association, which represents more than 140,000 occupational therapists, assistants and students, has named Sept. 16 National Backpack Awareness Day.

Shopping for practical backpacks is an annual tradition for Cumming mom Kathy David and her girls, Meaghan, 14, and Hannah, 10.

"What is comfortable and fits them well is first and foremost," David says.

These five tips for buying and using a backpack can help during back-to-school shopping.

1. Pick one with padding.

Padding along theback and shoulders is crucial when determining a backpack's comfort factor, says Dr. David Marshall, medical director for Children's Healthcare of Atlanta's sports medicine program. Poor shoulder padding may result in shoulder pain as the weight of the backpack pulls downward. Backpacks with little back padding may increase the chance of uncomfortable items digging into your child's back.

"You might spend a little more money on a hearty backpack that has nice, thick, padded shoulder straps, but the thicker and the more padded, the more cover there's going to be when it's across your shoulders," Marshall says.

2. Get the right size and features.

The height of the backpack should extend from about 2 inches below the shoulder blades to the waist (or slightly above the waist), according to the AOTA. Backpacks with a hip or chest belt relieve the strain on neck and shoulder muscles and improve balance, the association advises.

3. Fit the straps.

Test out the backpack by fitting the straps so that the backpack is snug against your child's back. Although kids may prefer to hang their backpacks loosely from their backs, tightening the straps keeps the weight closer to their body, saving a child from back, shoulder and neck pain. "The lower the backpack is, the more pressure there is on the shoulders, causing them to arch their back or have bad posture," says Marshall.

Another unhealthy way to wear a backpack is slung over only one shoulder. This habit puts all the backpack's weight on one side of your child's body, causing them to strain to stay upright and encouraging bad posture. Marshall recommends that children always wear both shoulder straps for proper support and evenly distributed weight.

4. Pack the bag correctly.

Organize your child's backpack and distribute the weight to increase stability and reduce aches and pains. Heavier items, like thick textbooks and binders, should be packed in the large center pocket and closest to your child's back. Smaller, lighter items, like pencil cases and clothing, should be packed in the front or in side pockets. Use the different compartments to distribute the weight, the AOTA advises.

5. Check the weight.

With school materials such as books and tablets, lunch boxes, and other items weighing on your child's back, monitor how heavy the backpacks are becoming. Pediatricians and the AOTA recommend that a child's backpack should weigh no more than 10 percent of his or her body weight.

With kids generally more out of shape than they were the past, tight hamstrings or poor core strength can predisposed them to lower back pain, and an improper backpack will only make the risk worse, Marshall says.

Cumming mom Stacy Cragg, 39, noticed her daughter Hannah's backpack getting heavier in the fifth grade and wanted to lighten her load.

"I tell her to only bring home the necessary items," Cragg says. "If she knows she can split it up, I tell her to go ahead and split it up. Bring some things home one night and other things home the next night."

Best backpack brands

Parents and students recommend these backpack brands for their comfort, support, durability and style. You can find these brands at mass retailers, department stores, sporting goods stores and online.

JanSport: Prices as low as $30 and dozens of colors and designs available.

Under Armour: These backpacks, averaging about $50-$60, offer more bells and whistles, such as padded laptop sleeves, water-proof linings and durable, comfortable design. "She had it all year last year, and it looks barely worn," Cragg says, of her daughter's backpack. "I think that even though they may cost a little more up front, they last a bit longer."

Land's End: With names like "My First," "Packable" and "FeatherLight," Land's End's backpacks are priced on average $40-$50.

The North Face: The North Face backpacks focus mostly on structure and comfort, whether at school or out for an adventure. The North Face offers high-end (averaging $80-$130), water-proof and durable backpacks.

Columbia: Super-compact, yet roomy, backpacks range from $30-$80, on average, with necessities, such as padded straps and compartmentalized pockets.