Mentally, you may have a tougher time dealing with the monotony of the treadmill.
精神上，你也许有一段艰难的时间跟跑步机的单调斗争。
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Mentally, you may have a tougher time dealing with the monotony of the treadmill. (Here are some tricks for beating boredom on the treadmill.) it's easier to distract yourself when running outside.
精神上，你也许有一段艰难的时间跟跑步机的单调斗争。(这儿有一些技巧克服无聊)。
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You must be thinking "he must be following a strict diet and spending tons of time on the treadmill" that can't be further from the truth.