A.N. OK, not really sure where this came from. Just John Watson + treadmill + tension = happiness. It will hopefully end up as four or five short chapters and is just a bit of nonsense. Apologies in advance for any errors in my medical terminology, I'm a bit distracted when it comes to describing John's muscles...

Chapter One - Explanation

DISCLAIMER: None of the characters belong to me, but the treadmill does.

The flat was quiet. Not silent; John was reading the newspaper and that rustled as he turned pages, and Sherlock was writing long passages on notepad and that made sharp rhythmic scribbling noises. But the sounds were hushed and peaceful, just the way John liked them on a Sunday afternoon. He might even make himself get up in a minute and make some tea. There were some chocolate hobnobs hidden in the back of the cupboard, they might still be there.

"John?"

Oh no. This was going to be bad. He could tell already. Sherlock had that voice on. The one that accompanied slightly widened eyes and the power to persuade and wheedle anything out of anyone.

"No." And that was final. He put the paper down in preparation of leaving the room. Those biscuits were calling.

"Oh."

He sat back again. Was that it? Surely Sherlock wasn't giving up already? No, John knew him better than that. His flatmate may be silent, but he would be planning now, forming some new devious strategy to convince John to perform to his will. Most likely without him even knowing. And so it began.

John stopped wondering what he was going to do and questioned what he was doing right now. It was something scientific, involving calculations and diagrams. He was immediately glad he had refused.

He looked over to the coffee table, curious, but trying not to appear so. Beside the laptop (his) was an open book of anatomical diagrams (also his) and sheets of papers scrawled with drawings and notes (not his) and topped with a photograph of a naked pair of legs (definitely not his!).

Hang on... Yes they were.

Why did Sherlock have a picture of his legs? And how the heck had he snuck that one? He peered around again to try and snatch a glance of the background, but Sherlock snapped the folder shut, giving him a significant look. If he wasn't going to be any part of it then he wouldn't get to see any part of it. The computer was lifted onto Sherlock's lean lap, turned purposefully so John could see nothing of the screen. He felt his eye twitch with the clicks of the keyboard.

A few minutes later, minutes that seemed long to John trying to fight his curiosity, Sherlock spoke again, "Before I agree to this contract at the gym to try and find a willing volunteer, and pay twelve months membership fees upfront as per the sickeningly avaricious terms and conditions, can I just confirm that you are unwilling to assist me in this particular study?"

John sighed, knowing Sherlock's strategy has almost succeeded. Obviously, seeing as he was considering agreeing just to find out what it was all about. "What study?"

Sherlock raised his eyebrows, through presumably not in surprise.

"No, no, no. Don't do that. You have to fill me in on the particulars before I will even agree to consider playing any part in it." He had learned that lesson the hard way.

"If I were to borrow or purchase a treadmill would you run on it for me?"

It was John's eyebrows' turn now. That sounded far too simple. "Elaborate."

"I wish to perform a study in the development of musculature. And I'd much rather do it here than in a gym."

"Method?"

"I would require you to 'run' twice a day for a minimum of ten days."

"Purpose?"

"To study the movement and growth, mainly of the quadriceps femoris and the gastrocnemius, but the observation will hopefully cover all the major muscles in your legs, and how they change and develop as you become accustomed to the exertion."

"Would you be harassing strangers if I refuse?"

"Undoubtedly."

"What's the catch?" Because there was one. There had to be. There always was. Often more than one. Though it sounded, even to him, as though he were already agreeing to participate. Maybe he was. The idea of being an example of the perfect human form for Sherlock to study hit a chord in him, sending it humming and thrumming. He could do it, sure he could. Unless there was a catch...

"You would be barefoot."

That couldn't be it. That didn't sound too terrible. In fact it made perfect sense; humans were designed to run barefoot. "How much running? How far?"

Ah, judging from the sudden loss of eye contact, that was it. Sherlock shuffled his papers around for a second, "Well, I am, as yet... Uncertain."

John was not fooled. "How far?"

"As far as you can."