当你弯曲肘部时，肱二头肌会收缩。

The ___biceps contract when you bend your elbow.

他展示了他强壮的肱二头肌。

He is showing off his ___biceps.

他每天做俯卧撑来锻炼他的二头肌。

He does push-ups every day to strengthen his ___biceps.

跑步后记得拉伸你的二头肌以避免抽筋。

Remember to stretch your ___biceps after running to prevent cramps.