Scalenes ("thoracic outlet" and "carpal tunnel" syndromes; chest, arm, and upper back pain). You may think you're having a heart attack. Get it checked! If no cardiac problems are found, consider other muscles, especially if you have tingly thumb or index fingers. Scalenes contribute to severe tension headache. They are one of the leading causes of "carpal tunnel syndrome." On the list of a half-dozen possible causes, the carpal tunnel itself is dead last. Check before you cut!