Emily always was a competitive girl. She wasn't a strict feminist, but took offense at any suggestion that men possess greater physical prowess than women. She's certainly stronger and faster than most women.
Emily and I dated for years, and lived together for a while. She's of pretty average height and weight, has long blond hair, beautiful blue eyes, and large, natural breasts. My natural male strength advantage occasionally frustrated her, and I took advantage of her competitive side one night, in a good natured way.
Occasionally we would wrestle around with each other in bed, often partially dressed or fully naked. It was mostly just goofing around, but occasionally her competitive side would kick in and we'd wrestle more seriously. We slept on a full-size futon on the floor, which made for a good little wrestling arena.
I would get very turned on wrestling around with my girlfriend, our bodies pressing together, rolling around in physical contact. Being a bit stronger than her, I could typically overpower her after a few minutes and pin her. Aroused, I would want to fuck her, but thanks to her competitive nature she'd want to keep wrestling. Even when I had her pinned down and tried to slip my dick into her, she would squirm and hold her pussy clenched tight, so I couldn't slip inside her.
"Ok, Emily," I said one night as we started rolling around. "I think we need some ground rules."
"What sort of rules?" she asked.
"Well, once I pin you I want to have sex," I replied.
"Sure, once I'm done wrestling we can have sex," she responded.
"No, I mean when I pin you I want you to let me screw you, right away."
"How come you get to make the rules?" she asked.
"Ok fine, let's make a bet. How long do you think it would take me to pin you?" I asked.
"I bet it would take at least ten minutes," she responded, and I couldn't help but chuckle, much to her annoyance.
"Ok, tell you what, let's make it five minutes. We'll set a timer and if I pin you in less than five minutes, I win your body. I get to fuck you any way I choose, cum any way I want for a whole night, without worrying about your pleasure," I replied.
"Fine. But if I win you have to give me a massage, and have sex with me the way I want to. And you have to do all the chores for a month. Laundry, vacuuming, washing dishes, all of it," Emily added.