Restricted Sprint?

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I don't think so. Not only is encumbrance and fatigue one of the most annoying features in games (it has absolutely no place in games - if I want to feel encumbered I'll go run a marathon while carrying a washing machine), it makes literally no sense within the horror idiom. The human body is capable of almost anything in times of intense fear - if you're running away from a monster you simply are not going to stop sprinting and suddenly start walking because of a want for energy. It's possible to completely wear out your muscles (to the point where you will be permanently injured) but the body certainly prefers that to dying - so you keep going for as long as physically possible.