Real failure is ones ability to not be able to do the negative of the lift. So you need a partner. when you get to the point you cant lift its not really failure. You should have a partner then when you get spotted up, properly do the negative lift its then complete failure. That is supposedly one way to workout.
So for chest press you have sompne spot you up when you cant lift it anymore. Then hold the weight up and let it hit chest. Have him lift it up again and repeat until you cant even let the weight to stay up in the negative motion.
It could be done that way or to positive failure etc. training partner is always good but not a must imo.
