something you might want to try is static workouts to failure-very little wear and tear on the joints and still working the muscle
this is where machines (Hammer Strength) comes into play-I have done many workouts with one static contraction to failure only and the next day my muscle was sore
right now my back is fucking hurt and I'm working 10 plus hours in the cold, the last thing I want to do is go to the gym and get hurt so I don't-not too hardcore, but if I get hurt (which I am already) I don't work and the bills don't get paid-as you get older you train smarter not harder