Fact—Injuries can happen. Aches, muscle fatigue and soreness are part of life for active people and those involved in athletic endeavors. There is a difference between the ache from overuse and the pain of an acute injury. Aches come and go, however, if left untreated they can become an injury. Learn how to decipher between an ache and an injury. Step 1: Identify the problem and then, treat it.