Tight muscles are not only frustrating and painful, but they’re inconvenient since they limit your movement. Worst of all, they can prevent you from continuing to do the things you enjoy. Knowing what causes muscle tightness can help you manage and prevent it from happening in the first place. Take a look at some of the reasons for muscle tightness. The Main Reason Your Muscles Tighten When the muscles are in a relaxed state, the fibers have little gaps in between them. As they are contracted in an activity, those bands come closer together. If these bands remain in a certain position for a long period of time or are.