I'm an endurance paddler www.hhcanclub.com and regularly do 3 sets of 10. I've a bar at work and i cycle in and then am nice and warm to do some pull ups. At Home I've just got a bar too. My two sons are doing it too now. So yesterday I did week 1 day 1 alone at work, then at home with son Tom and later after I'd helped a pool kayak coaching session with my other son Hugo. So three times I did 5 sets with 2 min intervals consisting of: 6; 6; 4; 7; 9, and for the last set I did 10 each time.