I hit 35 and just started to ache so much in the mornings. I'm not quite as fit as I used to keep and have had my fair share of riding accidents, which have had an impact on my range of movement. I find I get a lot of lower back pain during missionary, especially if the guy is small down there. It helps to put a cushion underneath. I have also noticed more neck and shoulder pain when giving oral if the guy is on his back. I have had to adapt a little bit and mention it if I feel uncomfortable these days.