Scientist liken voluntary or directed attention to a mental muscle that can wear out over time.

科学家把有意识注意力必做一块脑部肌肉，随着时间的流逝，它会一点点失去力气。

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He recommends intervals, hill repetitions, and tempo runs at least once a week to build your mental muscle.

他建议为了增强意志力，间歇跑，坡道重复跑，和乳酸门槛跑，至少每周一次。

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There are steps you can take to help reduce abdominal fat and maintain lean muscle mass as you age in order to protect both your physical and mental wellbeing.

你可以在年龄增长的过程中采取一些措施来减少腹部脂肪，保持精瘦肌肉含量，从而维持你的身心健康。

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There was a delay in muscle loss and brain shrinkage that lead to mental problems linked to aging.

VOA: special.2009.09.01

Each man knows that the other is a true adversary, and there is mental muscle, not just physical daring, at work on their private common ground.

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The brain is like a muscle, "Pro Mental Coach" says.

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Extending the UnNap Nap To make the UnNap Nap as close to a nap as possible, do a mental scan of the body, focusing on different muscle groups one at a time, stopping at any that are feeling tense.

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