I don’t believe a single bad exercise exists.
I don’t believe there is a single bad form of exercise either.
But you can make an exercise bad.
You can make a form of exercise bad.
It is how you do things that is most important.
It is the quality of your movement that is important.
If you have done thousands of push-ups using poor form, it will be difficult for you to ever learn to do them correctly.
It is also likely that your shoulders will be banged up.
What is really bad, is that if you have racked up thousands of reps, you probably think you are doing them correctly.
And when the aches and dysfunctions begin to set in is when you start to place blame on the exercise.
In reality, you deserve the blame.
It is never the tool’s fault, it’s the user’s.
Take time to truly understand every aspect of the movements and lifts you are performing.
Don’t develop, and especially don’t drill bad habits!