flex one's muscles

English

flex one's muscles (third-person singular simple present flexes one's muscles, present participle flexing one's muscles, simple past and past participle flexed one's muscles)

(literally) To tense and bend one's flexor muscles.
(figuratively) To show off one's strength or skills.
- 2010 January 21, “Choppy waters”, in The Economist:
  But at a time of a growing perception in the West that China is flexing its muscles [...], countries closer to China’s shores also worry that it might be getting more assertive.
- 2011 September 27, Alistair Magowan, “Bayern Munich 2 - 0 Man City”, in BBC Sport‎^[1]:
  Gomez's goals were his 10th and 11th of the season but only Hart's excellence prevented that total being extended, as the four-time European Cup winners flexed their muscles.

to tense and bend one's flexor muscles

to make a show of strength