If “no pain, no gain” is your motto at the gym, you could be setting yourself up for serious injury. “People need to understand within their body what pain is,” said Williams. “There’s a difference between discomfort and pain.” And often times, pain is a symptom of more than a hard workout—it indicates an injury.

Is there such a thing as a “good sore” during a workout? It’s possible, says Williams. For example, if you are working to build strength and endurance in your legs with a squat workout, you may experience some burning in your muscles during exercise. That burn is the lactic acid moving out of the muscles and the feeling should go away 30 seconds to one minute after you stop exercising. According to Williams, this is the only form of pain during a workout that is acceptable and sometimes even necessary. Long-lasting pain or soreness for days after a workout is unnecessary and can lead to overtraining and injury.

“You don’t have to have pain to get results,” said Williams.

Another misconception about pain during a workout is that if you experience pain during exercise, you simply need to work through it. What you really need to do is to rest those muscles, said Williams. “Resting is just as important as the workout itself, and is the only way to ensure your muscles are ready to go the next time you hit the gym.”