I'm a 4.0 player. 36 years old. I play about 2 time a week and try to play 1 tournament a month. I'm in decent shape...I do martial arts, power walk, hike, play basketball. If I play 2-3 sets in a day my body handles it fine. But 4 or 5 sets in a day...and my body really feels the pain especially my back. I was curious...just a survey for u players...How many sets can you play before it really takes a toll on your body?