Most people believe that all exercises are good, safe and effective. After all it's exercise—and that has to count for something, doesn't it?
The truth is that some common exercises aren't safe at all (especially for people who have muscle, joint, and health problems). Certain exercises require a bit more know-how than the average person possesses. And other exercises are downright wastes of your time.
But before we examine some of the most controversial exercises, I want to make it clear that every exercise on this list isn't always unsafe or ineffective for everyone. What you should do—or avoid—depends on your goals, fitness level, health history, workout schedule, and other personal issues. An article like this can't replace your own efforts to identify your goals and needs. That requires you to do some research on your own, talk to your medical professional about any pain or physical limitations you have, and learn how to exercise with proper form and technique.