Flex Friday is an ongoing trend on Instagram that is exploding with popularity. Basically one waits for Friday to arrive to flex some muscles, take a picture, hashtag #FlexFriday and post it for followers to view and admire.

There are pictures of people flexing their biceps, triceps, backs, quads or calves, but some people take it to the extreme by posting pictures of themselves flexing their money and showing off their vehicles, healthy meals, and protein shakes.