i've been tackled by a female rugby player willingly to see how much force is exerted in games (i'm a mosh pit addict, so i knew i could handle it. i flew away a good 12 feet. funny thing about it was that she's of average build (5'4, 110 lbs about...). i may be on the lean side(5'8, 140 lbs), but it does prove that huge muscles don't always equate with brute force.
regarding sports injuries versus obsession: not a fair fight. proof: france is obsessed with football (soccer) and rugby(regional preferences apply). just about the same amount of injuries in both, despite rugby being way more physical contact-wise than soccer.
america is obsessed with baseball, football, and hockey as pastimes, with regional preferences as always. injuries don't factor in the popularity factor. otherwise, why would cricket be even played? it's a sport dangerous enough to break bones with a throw, and deaths are not unheard of.
i don't have anything more than personnal conjecture, but women's sports tend to be more aggressive than male sports, if only for the belief that girls aren't as strong as boys, and i believe they overcompensate. i do know for a fact that i much prefer sparring with a goliath than with a girl my build or smaller. maybe sparring with a bastard sword is dangerous enough on its own, but girls are ferocious, like it's a point of pride to take down boys.
(girls, now's your chance to increase my knowledge, prove or disprove please, i'm interested)
edit: @freako104: boxing is less fighting than mma or savatte. you're only allowed punches, for one. i'm not saying i enjoy boxing, but as stated above, i do european medieval martial arts. sparring matches are closer to fighting when you wear period armor (gambeson, mail, gauntlets, helmets, shields...) and go against 3lbs of dull steel. i don't like boxing because as a sport, it's not to my taste. but it's not exactly brawling either.