Funny, but while I was at PT yesterday doing a pulley exercise for my shoulder, I looked at my wife and she was exercising her arms in the chair she was sitting in front of me. I looked at her and said "go for it!". I remember when I went to PT for my hip replacement, the Physical Therapist put me on a treadmill for a few minutes and my wife got on the other treadmill and started exercising. This was at 7AM and it was just us and one Therapist there.
When my shoulder gets back to "good" ROM, and I'm no longer in a sling, we will go back to playing our Wii Game.........which can definitely build up a sweat for both of us.
During the summer months, after my wife gets off of work, we like to take a walk around our apt. complex.
On the weekends, when the weather is right for it, our power boat will go out. That is definitely exercise!
And, then there is the Gun And Rife Range that we members of and go to during the year. Another definite exercise thing we do.