Gains

It was a moderately slow day at the gym, but among the few people that were there were Toni and Tiffany, the latter flexing in front of a mirror, and the former doing bicep curls with a hand weight.  They looked very much alike and were lacking in things such as different interests or depth of personality that would set ordinary people apart.  But theirs was not an unhappy life, and they got along well.

"Lookin' good bro," Toni said, doing a rep.

"Thanks bro," Tiffany replied, striking another pose.

From the changing room came Donna, a tanned brunette, well-built and muscular, dressed in a dark blue unitard, with her hair tied back in a ponytail.  There was no jealousy towards her, for all admired and respected her devotion to fitness.  There was no hate, for she bore none towards others, always willing to spot them when they lifted and sharing her recipes for goji and stevia muffins or activated almonds.  Others may have owned the building and run it, but she was the true boss of the gym. "Morning, bros."

"Bro!" they called out in unison.

Donna slung a towel over her shoulder, inspecting the gym, and her eyes fell on a machine that wasn't there the day before.  It was an odd assembly of grips, presses, pistons, and bars, looking somewhat like machines she was familiar with yet not at all like any in particular. "What's this?"

"That's..." Toni lowered her voice to an awed whisper. "That's the Glutinizer 5000, bro.  The most extreme workout device ever made."

Tiffany turned to her. "I thought the Glutinizer 5000 was a myth, bro."

She shook her head. "No bro.  It was banned in fifteen countries because the gains were too sick."

Donna stroked her chin. "Too sick gains?  Is such a thing even possible?"

"I don't know, bro," Toni said, "but we've all been too afraid to try it."

She nodded. "I'll do it.  We'll find out for sure."

"Good luck, bro," they said in unison.

The Glutinizer 5000 looked more intimidating up close, not being very obvious to Donna as to how it functioned at first.  Fortunately there was a pictographic instruction manual hanging from one of the sides and, after some trial and error, she put herself into a position to use it.  Gripping the handles, she put her feet beneath the straps and put the machine into motion, performing several repetitions that seemingly combined elements of splits, squats, curls, and crunches at random, along with motions that heretofore had not been developed by conventional fitness experts.

After only a few such motions the results were apparent: Her arms and legs were visibly thicker, though what they gained in size they lost in muscular definition.  Her trim abs and waist, too, were ever so slightly larger.  Donna paused to flex, testing her new assets.  She had gained them quickly, and they were sick, but certainly not -too- sick.  This needed to be looked into further, she thought, and resumed her workout.

She soon slipped into her zone, only aware that something was providing resistance and assuming that it was the machine.  Nothing could be further from the truth, as her limbs grew wider, the defined curves soon becoming undefined; any resistance came from her own body, overcome by her innate strength.  The trimness of her abs, too, disappeared, replaced with a growing paunch, and up above that her chest was slowly gaining cup sizes.

Eventually these changes were noticed by Toni and Tiffany, who had put their own workouts on hold to watch her. "Bro," Toni said, "you're looking a little strange."

"I feel the gains," Donna grunted between motions.

"Those gains might be too sick," Tiffany replied, "even for you."

"Just keep spotting me, bros."

By now Donna's entire body was well beyond mere plumpness.  In a way she looked fat, but lacked any wrinkles or cellulite.  Indeed, her new size had no weight to it, squishing and shifting as she moved.  From deep within her zone she was aware of some newfound jiggling and the beginnings of a wedgie as her unitard rode up between her larger cheeks, but she ignored it, even as the same outfit stretched across her breasts and belly.

A moment later a middle-aged man approached the two young women, asking why there was an overweight pregnant woman using the equipment.  Toni and Tiffany attempted to explain that this was not the case, but not being the most gifted individuals in rhetoric, found some difficulty.  Eventually Tiffany looked over at Donna and hit upon a solution, explaining to him that she wasn't pregnant.  After all, her breasts had significantly grown in the interim, and her belly was now too large to -be- pregnant, therefore she must not be.  He left without protest, though neither saw his reaction, but he left nonetheless and both were pleased with what happened.

"Good job bro," Toni said.

"Thanks bro," Tiffany replied.  After a few seconds realization hit her and she turned back to Donna. "Wait, did I say she was even bigger?"

Bigger before, now larger still, Donna's limbs were bulging cones, bending only with great difficulty on her part.  Her unitard was positively overstuffed, looking as if someone shoved two volleyballs into the top and stretched to translucency across a yoga ball-sized belly with a popped-out navel.  Her face was red and sweating from the exertion, each movement generating a pneumatic creak, and both young women were almost certain it wasn't coming from the machine.

"Bro!" Tiffany shouted. "You gotta stop!"

Donna gritted her teeth, shaking her head as she forced the words out. "Just... a few more... reps." She brought her arms together, and there was a quiet ripping as the front of her unitard began to tear.

"Bro, your gains are -too sick!-  You're too swole!"

She shook her head again, crouching and pushing the bars up.  The unitard split from between her legs to below her breasts, pulling back and exposing a belly that faded to an angry shade of red around the navel.  Terrified, Toni grabbed Tiffany by the arm and pulled her behind a sturdy-looking stack of barbells, the two of them taking cover.

Donna's arms shook as she struggled to move the bars, and her entire body seemed to heave and quiver.  A loud creaking filled the air as she brought her arms forward, and she grunted out, "muh... gains..." a second before a deafening bang filled the air.

Tiffany peeked out, relieved that the rest of the building was still there.  A flattened, deflated Donna was draped over one of the arms of the machine, covered in the tattered remains of her unitard.

"Oh no," Tiffany exclaimed, rushing over to her. "Your gains!"  She picked her up gingerly by the shoulders, carrying her towards the juice bar. "Don't worry bro, a few protein shakes and you'll be good as new!"