From Nordic Larp Wiki
Player fatigue refers to players being exhausted because of the larp.
Player fatigue usually originates from violence, intimacy, hunger, thirst, lack of sleep, lack of shelter or lack of sanitation. Replacement rules are often use to shield the players from fatigue in larps where the characters are likely to suffer from fatigue.
Impact on roleplaying
Fatigue reduces the players capacity to play a larp in a way that contributes to a good experience for themselves and others. However, if the players play characters suffering from fatigue, the player fatigue can also be useful for a stronger immersive experience and more realistic roleplay.
Impact on player safety
Insufficient shielding from fatigue can influence the player safety of a larp, both because the players ability to make wise decisions on safety issues may be impaired and because the fatigue can be dangerous in itself.