Webster's Dictionary calls a sport 'a source of diversion'. By that definition, you are already a world-class sportsman in the sport of lap-based web browsing.
Want to know when else you are playing a sport? Take the test.
1. Competition. Am I competing with someone? Jogging isn't a sport. Running the 100-dash versus Ben Johnson pumped up full of starting fluid is a sport.
2. Physical exertion. Have I broken a sweat? If you sweat all the time, you're probably not playing a sport.
3. Risk of injury. Will I be able to explain a compound fracture by simply stating the name of this activity?
4. Presence of fans. Is anyone watching the competition? Not watching your legs cheerleaders, watching the competition.
5. Equipment simplicity. Could the equipment in this sport be reproduced with Bronze Age technology? Hint: If your equipment is breathing it isn't a sport.
Now you know. Sorry to those NASCAR and Texas Hold 'Em fans who thought they were watching sports. Remember, if it's televised during the World Series or the Super Bowl, it's not a sport.