The phrase "flex for" is grammatically correct and can be used in written English.
Example: "I need to flex for my job interview tomorrow by practicing my answers and improving my body language."
"My Jackie Chan Cable Flex for Your Bun and Thigh Max," reads one.
It enveloped his wrist and part of his thumb Wednesday, though it was cut back to let his wrist flex for today's practice.
A company called Flex, for instance, which makes a disposable disc designed to allow women to have mess-free sex on their period, raised north of four million dollars in the year after it was founded.
The young John, weary of being tanned with a paternal flex for missing his notes, had fled his home; returning in middle age for his ailing mother, he ended up "playing his father's big music … again and again … There need be nothing else".
That sexist, threatening backdrop can also be heard on a track such as Mr Difficult, when she sings: "I'm just a ratchet kid that sits here stretching out my thighs / Between the drills / But I'd never flex for your benefit," she's drawing on a long, rich history of hostile male attention.
These are flexed slowly, kept flexed for a few seconds in the air and then extended briskly, thumping the soil violently.
Inevitably, this will include some girls, but at first the boys are flexing for one another.
You'd love seeing all those celebrities on the red carpet, flexing for the cameras in their bicycle shorts.
Boxed into a corner of some cold stone palace, he is tensely flexed for any hostile action.
Afterward, Poundstone tore off his shirt and flexed for the crowd, just as Jan Todd had predicted.
