Amy clopped along through the aisles, huffing through her larger nostrils. The air was pretty dry inside the old place, and she was getting thirsty. Licking her lips with a much larger and darker tongue, Amy looked around. As if the store had anticipated her desires, Amy had stopped right at a vending machine. It appeared to be some sort of protein shake dispenser.
"Well, it's not water, but it'll do." Amy said as she peered at it, examining the drinks it carried. The options all had odd names, and no brands she recognized, though after her adventures in the store so far, she knew immediately what they would do.
Her eyes scrolled down the buttons, and she quietly read them aloud to herself.
"Brawneeiighh Bull, Pumped-Up Pig, Deadlift Donkeiighy....Ah!" she said excitedly, "Maximum Mare! That'll do it!"
Excitedly, she pulled out a dollar and fed it into the machine, once it registered she quickly pressed the button for 'Maximum Mare', her hoof-like fingers clacking against the plastic of the machine.
"Thank you for drinking with us today," said a pleasant female voice.
She heard the machine whirr and shake. In a minute, a bottle dropped into the dispenser at her knees. It had a bright blue label, with the words 'Maximum Mare' emblazoned on it in stylish pink lettering. The plastic was an opaque white, so she popped off the blue cap and squinted inside, holding the bottle under the store's lights. A thick tan liquid filled the bottle. Putting her short muzzle at the tip, she inhaled deeply, her big nostrils flaring. A heavenly smell filled her nose, like a combination of peanut butter and apples.
The pupils of her darker eyes dilated and she quickly lifted the bottle and took a big big gulp, messily spilling some about her face.
"Mmm!" she licked her lips. "That's deeighlicious!"
Amy greedily chugged the rest of the thick shake, not caring that she was spilling some more down her face. She finished the bottle with a satisfied "Aaaah!" and cleaned the excess drink off her lips and nostrils with her big mare tongue. She dumped the bottle into a recycling bin next to the vending machine.
"Thanks!" she said happily to the machine before skipping through the store. She was almost at that aisle where she thought Lina might be, and the delicious drink had revitalized her spirits and given her an energy boost, as if she wasn't already having fun slowly transforming into a horse girl.
She was just two aisles past the vending machine when her stomach suddenly gurgled painfully. "Oh geez," she thought to herself. "I probably shouldn't have been jumping around like that..." She clutched her furry stomach with both arms, unable to stand up straight. She hoped she didn't have cramps too badly.
But to Amy's surprise, the cramps faded rather quickly. It felt like the protein shake was spreading out of her stomach, but not going where it was supposed to. Her body heated up, tingling sensations starting in her core and spreading out along her extremities. Looking down at her arms, she felt her muscles start twitching and expanding. "Whoa!" she said, feeling similar growth in her legs as her thighs began pulsing and pushing against her yoga pants.
She barely had time to marvel at her growing muscles before the tingling dove deeper, into her very bones. Amy braced herself against the nearest shelf as she felt a tremendous creaking and groaning come from her body as it began to grow larger. Her legs grew longer even as thick and shapely muscle packed onto her thighs. The legs of her pants, already stretched from the altered shape of her new hooves, began sliding up her shins as her news legs sent her closer to the ceiling.
Her arms continued plumping up, even as they slid out longer and longer. The tingling heat flowed back up her arms and legs. Amy felt a pressure in her shoulders and hips, and grimaced slightly as she felt both press outward. Her shoulders stopped rather quickly to match her arms, but her hips kept going and going, stretching the waist of her already strained pants.
The energy coursing through her body coalesced at the base of her neck and the start of her tail. She tilted her head towards the ceiling as the vertebrae in her neck expanded further, pushed her horsey face away from her body by about 6 inches. The rest of her spine soon followed, bones cricking and popping as her frame grew to match her arms and legs in proportion.
The energy spread all throughout her torso now, and her breathing became labored as she felt her organs growing and pressing against her still-human ribcage. That was rectified quickly, as in several short bursts, her ribs expanded, barreling out slightly and giving her a much thicker frame. The muscles in her stomach, chest, shoulders, and neck all started to catch up with her strengthened limbs. She felt her abs tighten, her shoulders puff up, and cords of muscle slid along her neck beneath her black mane. Her small t-shirt strained at this new growth, and she pulled at the shirt's collar that was now pressing into her throat slightly.
It seemed for a moment that the drink's effects were done, but two final jolts lanced out from her core, resulting in a wave of pressure and heat in her chest and rear.
Looking down, Amy saw that her breasts were slowly growing larger, pushing her already tight t-shirt to its limit. "What the hell?" she stammered, feeling the bra tightening under the strain, as the bottom hem of her shirt rose higher and higher up her midriff.
Her breasts were almost numb with heat, but her back was clearly in pain from the tightening bra strap. Ignoring the pressure in her rear, she thrust her hands up the back of her shirt and struggled to undo the clasp. It would have been hard enough with all the distracting sensations, but her new hoof-hands were also a fair bit less dexterous than before. However, her growing breasts solved that problem themselves, as a final surge from her breasts caused the clasp to snap apart on its own, and Amy breathed out a sigh of relief.
With that problem out of the way, Amy let her hands slide down to her overheating ass. Now she could tell that more and more flesh was pressing out, muscle and fat both. Her pair of leggings was making tearing and creaking sounds as small holes erupted along the surface of the fabric. Her ass continued pulsing, and each pulse was met with the sound of more tearing. She cupped the furred cheeks under her yoga pants, feeling the firm flesh filling her hands, thick muscles rippling at her touch.
Finally, the heat died down and the growing stopped.
Amy stood still for a moment, shaking slightly at the changes that had just overcome her. She felt something shifting around her breasts and reached underneath her shirt to remove the broken bra. She hadn't had very large breasts compared to most girls in college, but now she definitely had something worth bragging about. They strained against her shirt, and with her bra gone two thick nipples pressed proudly against the fabric.
Interested at the prospect of these new mammaries, Amy slowly lifted up her shirt and beheld her newly-grown DD breasts sitting firmly on her chest. Her nipples had grown bigger, thicker, and darker. She roamed her hands across them and felt a rush in her nethers as her legs twitched.
"Ooh" she moaned, her voice slightly lower again due to her enhanced physique. "That's gonna neeiigghdd some attention later."
She looked around and found a huge, 10 foot tall mirror sitting by the entrance to a nearby aisle. She was lucky it was a big one, as after a quick look at herself Amy didn't think she would fit in a regular mirror very well anymore!
She looked to be well over 6 and half feet tall now, maybe around 6'9" or 6'10". Her formerly slim form had filled out nicely, with shapely muscle that looked like she spent a fair bit of time at the gym, but not so much that she looked like some bodybuilder. She looked good, statuesque even. After giving another glance at her bigger breasts, she cast her eyes down appreciatively at her horse-enhanced ass.
It was quite a sight to behold, more than twice as big as her breasts in scale, firm flesh pressing against a pair of pants that looked just about done. Turning her rear towards the mirror, Amy flicked her tail, then flexed the muscles of her thick thighs and rear. With a final twanging sound, the synthetic fibers in her pants could take no more, and they burst off her lower half.
"Ohh!" said Amy in her dusky voice, sticking her hoof-hands down to cover her privates. "That's nneeiighoot good!"
"Well," she said to herself in embarrassment. "Guess I should have expected that shake to go all out after everything else I've seen heiigghre."
She clip-clopped off, awkwardly peeking her long neck around corners before jumping from aisle to aisle. Hopefully she could find Lina soon...or some pants that would fit her.