"Out of breath already, John?" Kiss. "Has Mrs Hudson been baking again?" Kiss.
"How about," Kiss. "You shut," Kiss. "Your face," Kiss. "And let me," Kiss. "Exercise?" This time when he sits up, John threads his fingers around the back of Sherlock's head and doesn't quite let their lips touch, "hm?"
Sherlock pouts, "you asked me to help."
"And you're doing brilliantly when words aren't coming out of," Kiss. "Here. How am I doing?"
"Fifteen. Halfway there."
"Brilliant." Kiss.
Sherlock rests his chin on John's knees, still rewarding him with a quick peck on the lips for every successful sit up, and watches his stomach ripple with each movement.
John grunts, "thirty," and flops backwards. His arms are thrown out to the side and his eyes slide closed while he catches his breath. Eventually he cracks open one eye, his breathing still slightly laboured, and puts his hands over Sherlock's to bring their faces centimetres away from each other, "why are you staring at me like that?"
"I can think of one or two other ways to burn calories," Sherlock purrs.
"And what's that?" John quirks an eyebrow, "if you think I'm gonna run around London without a criminal in front of me you have another thing coming."
With a sly smile, Sherlock parts John's knees and presses their foreheads together.
"No running involved."
He puts his hands on John's shoulders and gently pushes him back to the floor, following him down and lying across his chest.
John grins and wraps his legs around Sherlock's hips, "well you'd better get to it, Mr Exercise Expert."