Weight training
If an exercise causes sudden very sharp pain, with similarity to being cut with a knife, that is bad pain and you should stop the exercise. But all weight training exercises will slowly cause muscles to be tired and cause small strain in the muscle area they use. When some people say "no pain no gain" they mean the tired feeling and small strain will help make you stronger. But sharp sudden pain is bad and may mean someone was hurt (this will not help you be stronger).