Firstly, according to medical research, when we exercise, our brains release certain chemical substances which bring feelings of happiness and relaxation.

首先，根据医学研究表明，当我们运动的时候，我们的大脑会释放出某种化学物质，这将会让我们更加快乐、放松。

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Firstly, according to medical research, when we exercise, our brains release certain chemical substances which bring feelings of happiness and relaxation.

首先，根据医学研究表明，当我们运动的时候，我们的大脑会释放出某种化学物质，这将会让我们更加快乐、放松。

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