Her ass

With John's comments about her former trainer in her head Gwyneth know's what part of her body she wants to work on, "I was thinking, I'd like to tone my buttocks." She said.

"Great," John said, "I have the perfect workout for that. It's another new and radical one, but I'm hoping you'll be open to it. It will tone your butt in no time."

"That's great!" Gwen said enthusiastically, "I'm very open to it!"

"Ok, get down on all fours." John told her. She eagerly got down on her hands and knees. John knelt down behind her. "First, we need to warm up the muscles." He started massaging her ass, grabbing handfuls of it tightly and spreading her cheeks apart.

"That's actually quite nice." Gwyneth smiled.

"Then we make sure they're ready for the workout." He spanked her left cheek as hard as he could.

"Ow!" Gwen shouted, trying not to fall over. John followed up by spanking the other cheek, just as hard. Gwyneth winced again.

"Good, you are ready for the workout. Now close your eyes, and do everything I tell you without question. Are you ready?"

"Yes." Gwyneth said confidently, closing her eyes.

"Good, spread your legs a little further and push your ass back towards me." She did as she was told. "Good, now I'm going to do most of the work from now on, your job is to go with whatever happens and you'll have the perfect ass in no time. Are you ready?"

"Yes." Gwen said again confidently, smiling. But her expression soon changed as John spat on her asshole and rubbed it around with his finger. But as instructed she didn't question a thing. John then pulled out his dick and slowly pushed it into Gwyneth's asshole. "Ahhh!" She moaned, "What are you-"

"I said don't question it!" John interrupted.

"I'm sorry." Gwyneth responded, attempting to re-center herself. John kept sliding his dick into her asshole and she took it silently, with just the odd quiet moan or whimper. Once he was all the way in, he began to gently thrust in and out. He started gaining speed and ****, as Gwen's moans and whimpers got louder. Soon he was fucking her hard in the ass and she was taking it like a porn star. John grabbed her ponytail and pulled it back as he thrust.

"Do you feel the burn?" He asked.

"Yes, yes I feel it!" Gwen moaned.

"No pain, no gain." John laughed as he plowed her. He soon felt ready to cum.