Exercise doesn 't need to be strenuous in order to be beneficial .

为了有益锻炼不需要费力。

Training for a marathon is extremely strenuous .

为马拉松做准备是非常艰苦的。

Avoid strenuous exercise the day before so you go into your run with fresh legs .

避免在长距离跑之前做费力的训练，这样你就可以双腿充满活力的开始了。

Pregnant women should avoid all strenuous activities , but sewing is not one of them .

怀孕的女人应该避免所有繁重的活动，但是针线活不属于这种。

In fact , preparing baby food at home is not a strenuous task .

事实上，在家里准备婴儿食品也不是一件吃力的工作。