"The Promise of Sleep" - Breathing Space Blog
"Even though they have paid back several hours of sleep debt, they walk around like zombies all day Saturday, barely able to stay awake. The reason is obvious: you cannot pay back a weeks worth of sleep debt in one night. Less obvious: the stressful arousal of the weekday work place is no longer masking sleep debt on Saturday. As people tend to drink and eat more on weekends, their sleep fighting arousal is further suppressed."