What is this salty liquid coming out of my skin?

First day of physio and the old man got worked!!!!! or worked out!!!!!

1. 4 sets of leg lifts, 8 left leg lifts, 8 right leg lifts, and 10 lifts with both legs (on a machine)
2. 4 sets of step ups, 10 starting with the left leg, 10 starting with the right leg
3. 3 sets of squats while hold a bar on the wall
4. 5 minutes on the bike pedaling forward
5. 5 minutes on the bike pedaling in reverse

Now if you think that is amazing (which it is) add in that he's not tired, not sore (yet) and still happy.