expression, adverb
with all one's strength; as hard as one can
Used when someone exerts maximum physical or mental effort. Often appears with verbs like 走る, 押す, 叫ぶ, 頑張る.
彼は力一杯ボールを投げた。
He threw the ball with all his strength.
力一杯走ったが、
I ran as hard as I could, but I didn't make it in time.