Enjoying a lie-in at the weekend makes you sleepier during the week, according to new research.

一项新研究显示，周末睡懒觉会让你越睡越懒，精神更疲乏。

Experts say that contrary to popular belief, sleeping in on the weekends does not help catch up on sleep lost during the week, but rather makes you even dozier come Monday morning.

我们都认为周末睡懒觉能把上周的睡眠都补回来，其实恰恰相反，导师们说这反而会让你下周一感到更加的疲惫。

They say that a lie-in on Saturday or Sunday disrupts the body's internal clock so much that it can be more difficult to wake up for work on Monday.

导师们认为，周六或周日的懒觉会打乱身体内部的生物钟，从而周一会感到更难醒过来。

That is the finding of a study lead by Dr Gregory Carter, a sleep medicine specialist at the University of Texas Southwestern Medical Centre.

来自德克萨斯大学达拉斯西南医学中心的睡眠医学导师Gregory Carter博士带领研究这一项目。

He said: "A great myth of sleep deprivation is that if we miss sleep over the course of the working week, we need to catch up on an hour-by-hour basis on the weekend."

他表示：“睡眠缺失一大奥秘在于：如果我们在工作日睡眠不足，我们需要在周末一小时一小时的慢慢补回来。”

The daily, or circadian, cycles guide the body's internal clock. People can delay their circadian clock, up to one hour, by sleeping in one hour or more over the weekend.

日常的生理节奏的循环调控着体内的生物钟。人们最多可以在周末多睡一个小时来延迟生物钟。

The problem is that after sleeping in on weekends, the brain's circadian clock can be delayed up to two hours, making it tough to get to sleep Sunday and even more difficult to wake Monday morning.

但问题在于，周末睡得太多之后，大脑的生物钟就会延迟长达两小时，这样你周日的晚上就很难入睡，从而周一早晨更加难以起床。

Dr Carter says going to sleep earlier is more effective than sleeping in later. Balancing any "sleep debt" from the work week can be accomplished by spending eight hours in bed.

Carter 博士说睡得早比睡得晚效率要高很多。要想平衡自己工作日和周末的睡眠，的办法就是睡眠满足8小时。

He said that when people are really sleepy, their brains rest more efficiently.

他说，当人们真正感到困了，大脑才能休息的更好。

Dr Carter said: "To maintain our internal clock, we need to go to bed eight hours before our usual time for getting out of bed in the morning.Too many of us, however, stay up later on Friday and Saturday nights and choose to sleep in on Saturday and Sunday mornings.

Carter博士还说：“要想保持身体内部的生物钟，我们需要保证有8个小时的睡眠。我们大部分人都会选择周五或周六晚上熬夜，然后周六周日猛睡。”

"This pattern - combined with sleep-defeating actions that may include alcohol consumption and late-night checking of e-mails just prior to bedtime - makes for a painful Monday wake-up call."

“这种不健康的模式再加上一些耗费睡眠的行为（比如喝酒，或者临睡前熬夜查看邮件等），都会让你周一的起床变得痛苦无比。”