Editor's Note: (Before beginning any new exercise program, consult your doctor. Stop immediately if you experience pain.)
(CNN) Not all that long ago, people owned one generic pair of gym shoes, which they used for all sports and activities. Those days are long gone. Athletic footwear is a $16 billion business in the United States today. That figure is expected to grow rapidly over the next few years, as Americans buy multiple pairs of athletic shoes designed for different activities. But is it really necessary to have a closetful of sneakers, or is this all just marketing hype?
"All activities and sports require care in choosing specific shoes," said Dr. Bradley Schaeffer, a podiatrist and foot and ankle surgeon at New York City's Sole Podiatry. "You have to provide proper support to avoid creating or exacerbating conditions such as bunions, hammertoes, plantar fasciitis and ingrown toenails."
Working out in appropriate footwear also helps avoid overuse injuries, said Dr. Nelya Lobkova, a surgical podiatrist with Step Up Footcare in New York City. "It's especially important for the beginner or average participant, who is more prone to improper form."
Athletic shoes may enhance your athletic performance, too, as they are designed to provide the appropriate support and stability for a particular activity — like running. Since running involves a repetitive forward motion, a good running shoe will be light with a flexible outsole, which helps keep the foot moving while absorbing the impact of the foot striking the ground.
Hiking shoes, in contrast, have deeper tread patterns than running shoes to increase traction on uneven and natural surfaces, and they often come with higher uppers to provide ankle stability. Volleyball shoes, like many court shoes, provide support for movement in all directions, plus cushioning for the jumping that often occurs.
But don't toss out your gym shoes just yet. You only need to purchase sport-specific shoes if you're participating in a given activity more than twice per week, according to the American Podiatric Medical Association. And lacing up a pair of cross-trainers may work just fine if your weekly workout regimen involves several different activities, says the American Academy of Orthopaedic Surgeons.
Running, basketball, volleyball, hiking and tennis are some of the activities for which it's essential to have a sport-specific shoe, especially if you're a more serious athlete who wants to maximize your performance, said Dr. Damian Roussel, a podiatrist and foot and ankle surgeon with The Centers for Advanced Orthopaedics in Frederick, Maryland.
But with so many brands on the market, how do you know which is the best shoe for you? Generally, it's the one that fits your uniquely shaped foot the best. Unfortunately, most of us aren't so great at determining proper fit.
Between 63% and 72% of people are walking around in incorrectly sized footwear, especially older folks and people with diabetes, according to a 2018 meta-analysis published in the Journal of Foot and Ankle Research. The study review also found evidence that poorly fitted shoes can cause foot pain and disorders such as corns, calluses and deformities.
Since athletic footwear can't fulfill its purpose unless it fits well, it's crucial to determine the proper fit for your feet. To do so, experts from the AAOS recommend shopping at a store that specializes in your sport, and asking for help from a trained employee. It's also important to shop after a workout or at the end of the day, when your feet are a little swollen.
Make sure you try on both the right and left shoe, wearing the socks you typically use for this sport. The heel counter should hold your heel in place so there's no slippage, and there should be at least a half-inch (1.27 centimeters) of space between your longest toe and the tip of the shoe. You should also be able to easily wiggle your toes in the toe box; they should never feel constricted.
"Proper toe-box room, ill-fitting shoes and constricting shoes cause a lot of the problems I see in my practice," Schaeffer said.
Whatever you do, don't buy a not-quite-right pair of shoes, thinking you can break them in over time. You can't.
Once you've identified the right pair of shoes for your feet and brought them home, watch for signs of wear and tear over time. For if you use athletic shoes past their prime, that can also cause injuries.
"Any cracks or tears in the shoe construction demonstrate significant wear and breakdown," said Karena Wu, owner and clinical director of ActiveCare Physical Therapy in New York City. "If you lose that cushiony feeling, or you notice your performance being altered, that is also definitely a sign you need to replace your shoes."
But sometimes shoes look and feel fine, even when they are worn out. So another way to keep tabs on them is mileage and time. Running and walking shoes should be replaced after 300 to 500 miles of use (485 to 805 kilometers), Roussel said, and basketball shoes after 45 to 50 hours of play.
"For aerobic dance or tennis, replace shoes when they show signs of unevenness on a flat surface, or when they display noticeable creasing," he added.
Plan to replace other athletic shoes every six months if you're using them most days, say the experts with the American Council on Exercise. If you only exercise a few times a week, however, you might be able to keep them for a year.
Finally, don't wear your athletic shoes around town. They are not meant for that purpose, and casual usage will simply wear them out sooner.
"The feet are our foundation," Schaeffer said. "We must protect and support them to keep activity a regular part of our lives."