引(ひ)き締(し)まるto become tense, to be tightened

引(ひ)き締(し)まった筋肉(きんにく)は美(うつく)しいです。

Tightened muscles are beautiful. {to become tense, to be tightened}

モデルの引(ひ)き締(し)まった美(び)ボディに見惚(みほ)れる。

I'm fascinated by the model's tightened, beautiful body. {to become tense, to be tightened}

低迷(ていめい)していた相場(そうば)がいきなり引(ひ)き締(し)まり始(はじ)めました。

The market that had been sluggish suddenly began to tighten. {to become tense, to be tightened}

入社(にゅうしゃ)三(さん)年(ねん)目(め)にして大事(だいじ)な役(やく)を任(まか)されるなんて身(み)の引(ひ)き締(し)まる思(おも)いだ。

Being entrusted with an important role in the third year of joining the company makes me feel tense and tightened. {to become tense, to be tightened}

あの引(ひ)き締(し)まった顔(かお)を見(み)るに、あの選手(せんしゅ)は相当(そうとう)緊張(きんちょう)をしているのでしょう。

Judging by that tightened face, that player must be quite tense. {to become tense, to be tightened}