I agree with Karin. I do have clients who can’t perform a perfect push-up and I make them use the knee option. I also like to have clients try to do a push-up in an incline position by placing their hands either on a bench or a smith machine bar or a step (sometimes from the 2nd, 3rd or 4th step). This way they can still keep their body in a straight line and do a good push up (this option is also great for clients who have hard time getting on the ground). Once they get stronger then I lower the bar or have them perform the push up from a lower step.