flex your muscles

flex (one's) muscle(s)

1. Literally, to contract one's muscles, especially to demonstrate their size and strength. He's so vain, flexing his muscles in the mirror whenever he thinks no one is looking. She flexed her muscles and told us not to mess with her brother again.
2. By extension, to demonstrate one's influence, power, or strength. The small but outspoken nation has been flexing its muscles lately, with a wide range of military demonstrations. The wealthy business tycoon flexed his muscle to get the charges dropped against his son.
See also: flex
Farlex Dictionary of Idioms.

flex your muscles

or

flex your muscle

COMMON If people or organizations flex their muscles or flex their muscle, they behave in a way that is intended to show that they have power and are considering using it. A pro-democracy movement is starting to flex its muscles. The miners' actions last year seem to have encouraged workers in the oil industry to flex their industrial muscle.
See also: flex, muscle
Collins COBUILD Idioms Dictionary, 3rd ed.

flex your muscles

give a show of strength or power.
1998 Times Mr Prescott is flexing his muscles and the City is wondering just how far he is prepared to go.
See also: flex, muscle
Farlex Partner Idioms Dictionary

flex your ˈmuscles

show that you are ready and prepared to use your power, abilities, etc: He’s flexing his muscles, waiting for the day he becomes president.
Athletes flex (= stretch and tighten) their muscles before a race, a fight, a game, etc.
See also: flex, muscle
Farlex Partner Idioms Dictionary
See also:
  • flex
  • flex (one's) muscle(s)
  • flex muscles
  • flex one's muscles
  • muscle up
  • glutes
  • yokes
  • beer muscles
  • muscle
  • limber up
References in periodicals archive
is not a reason for you to go around and flex your muscles," Obama said.
China must 'abide by international law' in South China Sea dispute, Obama says
Pupils at King Edward VI sixth form college questioned the candidates after holding mock Euro elections of their own, as part of the county's Flex Your Muscles in Brussels campaign.
Students quiz poll hopefuls
The event was organised as part of Warwickshire County Council's "Flex Your Muscles in Brussels" campaign and also involved Age Concern.
European question time
Their in-school campaign has been prompted by Warwickshire County Council's Flex Your Muscles in Brussels campaign which aims to encourage more young people approaching voting age to take an interest in local elections.
Student 'elections'