There’s something off about your workout, but it’s not you. You’re completely dedicated to your schedule and know when to take rest days. So what if it’s your sneakers?

You should know when to replace your sneakers because they might just be affecting your workout. All you need is a table and your eyes.

Jacqueline Sutera, DPM, a board-certified podiatrist, spoke with Well+Good on how to know when your shoes are kaput and how replacing them can help prevent injury. According to Sutera, those worn-down shoes can, in fact, hurt you (even if you do love them). She explained to the outlet shoes with worn holes and heels can cause your foot to land at an increased angle and eventually cause “ligament injury, sprains, falls, tendonitis, pain in your hips, ankles, and back, and fasciitis.”

Basically, keeping those old tennis shoes is a bad idea. So, other than the obvious holes in them, how can you tell when your shoes need replacing?

According to Sutera, you should place your shoes on a tabletop. Then, assess the support. If it’s worn down, they’ve got to go. If the treading on the bottom is no longer gripping if you try to slide them along the table, they’ve also got to go. Finally, look at them from the back. If the shoes are unevenly worn down, if there are visible signs or damage or holes, or any cracking, it’s time for new tennis shoes.

While we understand how hard it is to find the perfect pair of sneakers, preventing exercise injuries is more important. If those toes are feeling tight, it’s time to go shopping.