A weekend lie-in doesn't make up for the hours of shut-eye lost by burning the candle at both ends in the days before, scientists say.
When sleep is regularly restricted to six hours per night - and it will not be improved after two nights of "recovery" sleep.
While having a lie-in helps people feel a bit more clear-headed, they are still slow.
Researcher Alexandros Vgontzas, a sleep expert and professor of psychiatry, monitored young men and women who spent 13 consecutive nights in his sleep lab.
They slept eight hours per night for the first four nights.
After that, their sleep was restricted to six hours per night for six nights, followed by three "recovery nights" of ten hours' sleep.
Dr Alexandros said: "After one work week of mild sleep deprivation, two recovery nights were adequate in improving sleepiness but not performance."


据英国《每日邮报》15日报道：科学家证实，周末睡懒觉并不能把前几天过度熬夜而缺的觉弥补回来。

如果人们每晚都是很有规律的只休息六个钟头，那么之后两个晚上的"恢复性"补觉对精力恢复也没有多大作用。
虽然睡懒觉有助于使人的头脑稍微清醒些，但是大脑的反应依然很缓慢。

研究员亚历山大是一位睡眠专家兼精神病学教授，他在自己的睡眠实验室里对一些年轻男士和女士进行了连续13个晚上的观测。

开始的四个晚上，这些人每晚休息八个小时。
之后的六个晚上，他们的睡眠时间被压缩到六个小时，然后在最后三个晚上进行每天十小时的"恢复性"睡眠。

亚历山大博士说："在持续一周的轻度缺觉之后，两个晚上的恢复性睡眠虽然可以让人不再犯困，但是这并不能改善大脑的工作效能。"

• expert [´ekspə:t] n.&a.专家；内行 (初中英语单词)
• adequate [´ædikwit] a.足够的；适当的 (初中英语单词)
• regularly [´regjuləli] ad.有规律地；经常地 (高中英语单词)
• recovery [ri´kʌvəri] n.重获；获得；恢复 (高中英语单词)
• weekend [´wi:kend, ,wi:k´end] n.周末休假 (英语四级单词)
• consecutive [kən´sekjutiv] a.连续的；连贯的 (英语六级单词)