expression
quick to act; cheerfully working; light on one's feet
Describes someone who readily gets up and does things without hesitation; often implies a willing, energetic attitude. Antonym: 腰が重い (slow to act).
See also: 腰の軽い
Antonyms: 腰が重い
彼は腰が軽いから、何でもすぐにやってくれる。
He's quick to act, so he'll do anything right away.
新しいプロジェクトにも腰が軽く参加した。
He cheerfully joined the new project without hesitation.
expression
Less common nuance; can imply acting too quickly without enough thought. Often context-dependent.
腰が軽すぎて、よく考えずに決めてしまう。
He's too hasty and often decides without thinking carefully.