体育锻炼exercise不可数的；exercise既是可数名词，同时也是不可数名词。exercise泛指“锻炼”时，做不可数名词，表示“体操”或“练习（题）”时是可数名词。
Diet and exercise are obviously important.
显然，饮食和运动是重要的。
You shouldn't exercise on a full stomach.
你不应该吃饱了就运动。
Which is better exercise ─ swimming or tennis?
游泳和网球，哪种运动比较好？
The heart responds well to energetic exercise.
心脏对剧烈运动反应良好。
Deep breathing exercises will help you relax.
深呼吸运动有助于放松自己。
Exercising regularly will pay dividends in the end.
经常运动最终会对身体大有好处的。
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