It all depends on the amount of games that you play at one time, and the speed at which you play all the games in that one set. I average about 10 games each practice session. If you play the games with no break between games, and within the games, no breaks between frames, then you can get a real work out. On a ten game set, this gets pretty exhausting, and I tend to sweat alot. During league, there are only three games, and the pace between frames and games is a lot slower. So I don't get physically tired during league.
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Ken - aka "dpunky" - Certified USBC Level I Coach