I may be asking the wrong people, but has this ever happened to any of you?

Sometimes my wife likes to be pounded fast and hard. I can usually do this for a good while, about 5 minutes at a time nonstop before I have to slow down a little, then start back up for another 5. I can do this for at least a total of 20 minutes if necessary, maybe more. It's not like I look at the clock.

We spoon most of the time because it's easier on us, and it leaves her access to her clit (or me). Missionary is the only position where this occurs, and we do multiple positions.

The problem is that when I do the missionary pounding sessions, afterwards, I can barely lift my right leg to put my shorts back on. Has anybody else had this problem before? My leg is not numb at all, just the muscles don't cooperate. Maybe a back problem? There's not any pain there.

I am 55 years old, and I'm not in as good a shape as I was in my 30s, but I am still in decent shape.