==Minimum sleep threshold== {{see also|Age}} Since vital sleep stages are generally not possible to reduce, the extent of compression required to sustain a schedule increases dramatically as total sleep time reduces. Compressing sleep, however, requires adaptation, and greater levels of compression necessitates harsher and/or longer adaptations. As such, schedules can be classified by their difficulty level, which is mostly a function of the amount of sleep cut.
由于必要睡眠阶段一般不能被减少，所以随着总睡眠时间的减少，维持一个时程所需的压缩程度也会急剧增加。然而，压缩睡眠是需要适应的，而更大程度的压缩则需要更严厉和/或更长的适应时间。因此，时程可以根据其睡眠减少的程度进行适应难度的分类。
