"Pulling" a muscle means that the muscle has been torn or overstretched a little bit. It's a painful situation that happens sometimes when you play sports, exercise, or move in a way that you're not used to.

Only muscles are "pulled". Similar problems that happen to other parts of the body include:

• spraining a joint (your ankle, wrist, etc.
• breaking a bone
• tearing a tendon (like the big tendon on the back of your foot which is called the "Achilles tendon"