be careful.
A friend of mine, who is in decent shape for someone in their mid 40's, was doing 100 a day to keep up with his HS boys. He ended up having some kind of muscle attack on his arms but wasn't sure at the time, went to the ER to rule out a heart attack.
Don't be afraid to go on your knees. At our age.... it's no joke. I used to bang out 25 at a time but my wrists and fingers started to develop some issues, i wear gloves now. But during our classes if we are doing chest or pushup work I get some 35 pound dumbells and do it that way.