During the medical test, he was asked to hold his breath for ten seconds.

hold 的意思是"保持、握住"，这里指"屏住"的动作。 breath 的意思是"呼吸"，指一次吸入或呼出的空气。 hold your breath 是一个固定短语，意思是"屏住呼吸"，指暂时停止呼吸的动作。