No exercise recommendations across the globe mention an upper limit for safe exercise, but perhaps there is one.

目前，全球尚无有关安全锻炼的上限建议，但或许应该有一个。

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In conclusion, walking is a cheap, safe, enjoyable, and readily available form of exercise.

综上所述，散步是一种廉价、安全、有趣而又随时可以开展的运动形式。

《柯林斯英汉双解大词典》

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Walking is safe. And,it is said be to as valuable for one's health as more intense forms of exercise like jogging.

VOA: special.2010.06.08

This year, we build further on this topic by highlighting the need to promote an open and free environment online for the safe exercise of press freedom in this arena.

UNESCO: World Press Freedom Day 2013

According to Lopez, studies also show that hope promotes healthy behaviors, including fruit and vegetable consumption, regular exercise, safe sex practices and quitting smoking.

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"That probably means you need to exercise even more, but the trainer has to understand how to work with that population and make exercise a safe experience, " she said.

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