Regardless of activity level, no one is immune to muscle strains. And what is a muscle strain? It’s damage to a muscle or tendon (AKA the tissue that attaches muscle to bone).(1,2) A strain can be as mild as over-stretching and as severe as tearing in the muscle or tendon. Muscle strains are not limited to athletes, either; you can strain a muscle by lifting something too heavy (say, a box of books, or an eager grandkid). Using one muscle over and over can cause strain, as can falling, reaching, turning your head too far or too quickly... the list goes on.(1)