I tried Google Translate and just get チェストアウト. Other dictionaries do not provide any meaningful results. This is a common phrase used in sports training. I cannot believe there is no Japanese equivalent.
1 Answer
As an imperative: 「胸{むね}を張{は}れ！」 or 「胸を張って！」
Name of a pose: 「胸を張るポーズ」、「胸を反{そ}らすポーズ」、「胸を突{つ}き出{だ}すポーズ」, etc.
Drop the 「ポーズ」 from the expressions above and you will have the verb phrases.
