John never really felt commited to the gym. It felt like a chore with each visit, barely spending an hour in there and never really leaving with a sweat. The most interesting thing was when he found a pair of earbuds left lying around, no one nearby to have been using them. He shrugged, putting them in his pocket. Finders keepers.
When he entered the gym the next time, he connected the earbuds and put them in. The world faded away as he started excercising, unable to focus on anything other than the equipment he used. It wasn't until he was drenched in sweat, completely exhausted unable to lift anymore when he noticed the time. He had spent all his free time in the gym working out.
He left confused, only to return the next day ready for more. All his free time started going into the gym, unable to spend time on anything else every time he put the headphones in. He couldn't stop himself until he was spent, and then he'd only have time to make it home and crash in bed.
His body quickly started growing, huge muscles rippling through his body as his arms swelled. He knew the earbuds were forcing him to exercise, but he didn't care. He loved the sight of his body growing bigger and bigger, his mind becoming a slave to the gym. He couldn't see anything other than his muscles, posing in front of mirrors flexing. There was nothing else in this world he could care about.