Proper form is mainly to prevent injury and to move the most weight the most efficiently but you can still get "gainz" by letting it slip slightly. A good examp

Proper form is mainly to prevent injury and to move the most weight the most efficiently but you can still get "gainz" by letting it slip slightly. A good example is elite level power lifters on a deadlift, they round their spines pretty awfully when they approach their 1 rep max but they are trading a potentially slipped disc for CNS improvement and moving a greater load. The trick is knowing when and how to let form breakdown just enough that it doesn't destroy you. Also there is merit in restricted range of motion training (such as stopping short of chest and lock out on bench press) to increase time under tension and "pump" - not considered proper form but if you want to target a certain muscle/group and really get it burning then it works very well.