8 Ways to Protect Yourself Against Tendinitis. Tendinitis is when you have severe swelling in one (or more) of your tendons, which are thick cords that attach bones to muscles. Few simple tips can help you steer clear of tendinitis before it hinders workouts and sports performance. 8 Ways to Protect Yourself Against Tendinitis : Believe it or not, tendinitis is common among athletes. This condition can be extremely painful, and can