From stiletto heels to tongue piercings, sometimes fashion trends verge on the side of danger. The newest trend in backpacks — messenger bags — may join the collection of fashion accessories that are not optimal for your health.

The ubiquitous messenger bag, a rectangular pack with outer flaps and one shoulder strap, started becoming trendy about five years ago. The bags were first worn by mostly by just girls and then later by both genders.

Messenger bags are sold at the Stanford Bookstore, and many people can be found wearing them on campus. Yet despite their popularity, they could be actually worse for your shoulders and spine than traditional backpacks.

Alina Liberman, a freshman, has been using a messenger bag since the first day of classes this year.

“I really regret buying my messenger bag,” Liberman said. “It’s annoying and hurts my back a lot.”

Liberman and other ailing students have a valid reason for complaining of back and shoulder pain. David Edell, a sports medicine specialist at Stanford Interventional Spine Center explained how this new trend could be harmful.

“Despite the fact that there is not a whole lot of research on messenger bags and how they affect one’s back, backpacks in general have been known to cause back problems when they are not worn properly or when they are too heavy,” he said.

Edell said that messenger bags have the same effect as a regular two strap backpack, except that all the weight of the bag is concentrated on one strap and therefore on one side of the body.

The weight is distributed completely along one muscle on the back called the trapezius muscle. Students using messenger bags usually try to compensate for the added pressure on their back by leaning to one side.

“In addition, a problem arises also because a messenger bag is situated so low on a student’s waist that it’s usually against the butt.” Edell said. “This will change the center of gravity for a person. Whereas the shape of a normal person’s back is in a rough S-shape, the messenger bag will add weight so that the top part of the S is flattened and the bottom part of the S is too curved. This will undoubtedly cause a lot of pain and discomfort to the back.”

Edell’s ideal backpack is one that resembles a hiker’s backpack, where the waist strap and both shoulder straps are worn. This distributes the weight evenly. The waist strap is essential because it ensures that the weight is distributed along a person’s legs, taking pressure off the back.

Some elementary schools require students to use rolling backpacks, a trend Edell supports.

“Then when they get to high school and college they will be used to using rolling backpacks, which take the pressure off the back entirely,” Edell added.

Tim Bowman, a physical therapist at the Vaden Student Health Center’s Physical Therapy Department, also agreed with most of Edell’s ideas. Bowman explained that using a messenger bag is the same as hanging your backpack by only one strap.

“The weight should be more evenly distributed,” he said. “If the weight is completely on one side of the back and the strap keeps falling off, then people will keep shrugging their shoulder up. The muscles on this side of the back will have to work harder to make up for the added pressure on the other side of the back.”

Bowman also commented that the way people usually wear messenger bags is incorrect. Students typically sport the bag by wearing the strap on one shoulder, letting it hang on their side.

Instead, Bowman said, “Messenger bags should be worn diagonally across the back, which distributes the weight most evenly and ensures that the strap won’t fall off.”

Bowman added that backpacks aren’t necessarily better than messenger bags, especially if students place very heavy books and water bottles in them.

“A backpack with a lot of weight in it will have too much weight located further out from the back, which pulls you back and compresses the spine,” he said. “Students will have to walk bent forward in this circumstance.”

Like Edell, Bowman supports the rolling backpack, but he said he understands that at Stanford — where most people uses a bike — this idea might not be practical. Bowman suggested getting a bike basket for books and binders.

“[Using a basket for your bike] removes the weight entirely from the back and gets rid of the problem,” he said.

Despite the potentially harmful effects of the messenger bag proposed by these experts, some students at Stanford reported that they have no problem with their messenger packs. Helen Snodgrass, a freshman, has two messenger bags, both of which she has started using this year.

“I like them a lot,” Snodgrass said. “Mine are never uncomfortable simply because I don’t put a lot of books in them. If I had to bring a lot of books, I would just use my regular backpack.”

Abel Romano, a freshman, said he had a similar opinion regarding the bags. He has been using his messenger bag for six months and has never felt any back discomfort.

“I love my messenger bag because of its functionality.” Romano said. “It’s great to use it when you only have to bring a notebook and a few other things to class. But if I had to bring more than one textbook, I would use a backpack.”

If they are used the proper way, messenger bags can be very useful and cause few health side effects. But perhaps, to be on the safe side, one could always stick with the traditional backpack.