The fake smile plastered across Heather’s face as she ran by Mark, her tits bouncing from side to side as her top was hiked almost up around her neck, hide the seething hatred the lay beneath the surface.

As she jogged out of sight, she felt her face relax and she managed to pull the top down over herself once more, she knew it wasn’t really worth the effort, no one else could see her at his private estate and she’d just be pulling it back up as she approached him on the next lap, but it gave her some sense of dignity, if only for a few minutes.

For his part, Mark was reclining in a sun-cot, sipping on a drink under the noon day sun as she ran her laps for the day.

She’d be in the pool next, doing the breast stroke of course, then in to the weight room to do squats too, as Mark said, “Work on her ass.”

She fought it, every moment of every day, but the stupid black bracelet around her left wrist gave her no choice in the matter and as many times as she’d tried to remove it, she’d never even come close.

As she approached Mark again she felt her arms move up and raise her top once more and then her mouth twist in to the happy grin as she ran by him.

Mark had been her boss, up until she’d resigned last week or course, he was doing research in to fitness trackers and he’d needed a test subject to try out his latest gadget, the black bracelet that adorned her even now.

At first it had been just like any other fitness tracker, counting her steps, monitoring her heart rate, the standard stuff.  But then, slowly, it had started prompting her to do things, like take a walk around the office.  Nothing major, just little things to improve her fitness.  

It felt good, an unfortunately by the time she realized it felt too good, it was too late.

Her mind had learned that doing what the tracker said resulted in pleasure and the more she did, the more pleasure came.

Soon “Take a walk” had been replaced with “Take a jog”, then “Go to the gym”.

“Get changed in to your workout clothes” had been replaced with “Wear skirts and tight tops” and then “Heels and short skirts”.

“Smile more and be nice” had become “Giggle and agree with Mark” and then “Do what Mark says”.

“Have a healthy lifestyle” had become “Masturbation is healthy” and then “Sex is the best exercise”.

I hadn’t taken long to find herself spending her evenings at the gym, her nights with a dildo between her legs and her days under Mark’s desk sucking his dick.

The thing was that she knew what was happening at every step of the way, but just powerless to resist the pleasure of following the trackers instructions.

She’d tried to disobey once, keep her fingers out of her pussy one night, she’d lasted a good hour of shivering and shaking, a gut wrenching fear in her gut until she’d broken down and crammed her biggest dildo in to her pussy and cum like hurricane.  Wet and with a force that nearly blew her away.

As she approached Mark once more the fitness tracker beeped and a wave of pleasure ran up her spine and exploded in her mind, another activity the tracker had assigned her was complete and she nearly came from it.

Instead of doing another lap, this time she turned to her right and towards Mark, the smile one her face, her tits hanging out as she checked the tracker, the little swimming icon flashing and she headed to the change room.

The tracker flashed several more times and the latest inspirational message came across it, “Naked sluts are happy sluts”.

She veered from the change room and headed right to the pool, pulling her top up over her head and then pulling her shorts down to her ankles, making sure to bend at the waist, then stepping out of them and diving in to the pool.

She had completed several lengths of the pool before she saw Mark standing at the end, watching as she executed a perfect breast stroke.  More pleasure ran through her, even though she knew she should hate it, showing off her body to Mark had become more and more pleasurable.

She finished up her laps under Mark’s watchful gaze and then, as the tracker instructed, headed in to the gym to do her squats.

As she squatted down and stood back up, two dumbbells in her hands, she seethed at Mark.

Since those first blowjobs at the office, she’d given him countless handjobs, he’d fucked here tits too many times to count and nearly chocked her to death with his dick more times than she liked to remember.

It was all good exercise, she knew, but he’d never let her have the best exercise possible and fucked her.

The tracker beeped once more and the pleasure came over her as she dropped the dumbbells to her side, then she looked at the tracker, her routine done for the day.

The display had a prompt on it, “Level 2 complete, would you like to advance to level 3?”

A shiver moved through her, maybe if she completed level 3 Mark would finally fuck her, a genuine smile crossed her lips as she tapped “Yes”.

“Congratulations, welcome to level 3!  Sex is the best exercise, but anal sex is even better!”

She dropped to her knees as the pleasure raced through her, her fingers dove in to her pussy, her other hand grabbed her nipple and pulled as the orgasm built and finally crested.

Mark looked on as Heather fell backwards, her fingers still in her pussy, it had been hard to hold out until she finished Level 2, but it would be better in the long run.

He’d be able to fuck her any time now, her legs would open wide at even the suggestion of sex and he was definitely going to enjoy her new found openness.

Of course, by the time she reached Level 4, she’d be begging him to fuck her ass as well, but that was still a few weeks away and he was sure he’d be able to hold out until then.

He stepped in to the gym and stood over her, “Ready for some more exercise Heather?” he asked.

She looked up and smiled at him as she spread her legs, it wasn’t hard to tell it was a real smile, he’d seen that fake smile across her face for far too long.

He bent down a positioned himself between her legs, soon that ass he’d been lusting after for years would finally be his.  He was pretty sure Heather would be happy about it in the end too, but if not, it didn’t really matter to him if the smile was genuine or not, as long as she flashed that beautiful smile at him as he fucked her ass, that was all that mattered.