Dictionary.com defines a sport as “an athletic activity requiring skill or physical prowess”. Professional esports players absolutely exhibit physical prowess and skill, which is finely tuned and meticulously trained. I also think that the mental exertion required for the top-level of esports trumps the physical exertion from some traditional sports.
The definition of sport is clearly shifting. Is competitive Cornhole a sport? Is chess a sport? (The IOC says yes). Is drone racing a sport?
Physical prowess requires physical activity. Sitting in a chair is not a physical activity. Mental exertion is not what makes something a sport, otherwise mathletes would be called athletes. You start getting way too broad when using your definition and you'd end up having to include all sorts of other things. Is competitive cooking a sport? Ice sculpting? Can competitive drawing be a sport now? They require similar skills to esports. The things that separate esports professionals and others has little to nothing to do with athleticism or physical prowess. Just so we're clear, I played StarCraft at a very high level (within the top 1% of all players) it had nothing to do with my athletic ability.
Cornhole is not a sport to me, no, and neither is chess. The IOC also removed wrestling, no? They're into making money not defining what sports are. Drone racing is not a sport. There are things that require physical activity that I personally wouldn't consider a sport either, but an athletic competition (think anything routine based or with judges only) but that gets into a whole other topic.
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Regarding the article, I think the growth of esports is great. It's really interesting to see how various communities react to the different ways in which they are presented games. I do think that games are kind of a challenge to corral though because it's an always changing landscape, from players, to patches for games, new games, and trends within the gaming communities.
I'm not sure one organization will ever be as big as some of the people in that article think.