They are alert at bedtime and sleepy when it is time to get up, and this may have nothing to do with how fatigued their bodies are, or how much sleep they must take to lose their fatigue.

他们在睡觉的时候很清醒，到了该起床的时候很困倦，这可能与他们的身体有多疲劳，或者需要多少睡眠才能消除疲劳无关。