"强身健体"是指通过锻炼身体和保持健康来提高身体素质和增强体能的行为。在英文中，这一概念可以用以下几个短语表达：

"Exercise regularly"：定期锻炼
"Stay fit"：保持健康
"Maintain good physical health"：保持良好的身体健康
"Improve physical fitness"：提高身体素质
"Enhance physical strength"：增强体能

例句：

I try to exercise regularly to stay fit and maintain good physical health.
I'm working on improving my physical fitness by pfting weights and running.
One way to enhance physical strength is by doing resistance training.