Never train with weights that are too heavy for you

This is not effective or proper weight training

Train with 60-80% of your maximum lift weight. This is the weight that allows you to make just one, but one correct repetition. This weight should allow you to execute between 6-10 repetitions until the muscle fails. In all gyms, you can observe how some trainers like to lift excessively heavy weights. This is not productive bodybuilding, and they are probably just showing off their egos. They are not effectively working their target muscles, since they are relying on other supporting muscles to help them lift the excessive weight. If they only chose a lighter weight, the benefits of exercising the target muscle would be improved by providing them with the optimum stimulus condition for muscle growth.