Shifting your circadian rhythm: How to become a (somewhat) earlier bird by using temperature

Chronotypes are mostly born, not made. Whether you’re a morning lark, intermediate third bird, or evening owl is largely determined by your genes. Yet, if you’re an intermediate or evening chronotype that has trouble getting up early for work, don’t despair.

Your circadian rhythm is also determined by things that you expose yourself to throughout the day. In this regard, your body temperature plays a crucial role. A rising temperature, which usually happens early in the day, makes you alert. A falling temperature, which usually happens later in the day, makes you sleepy.

Accordingly, increasing your body temperature early in the day signals to your circadian clock that it is daytime – and thus makes you more alert and less sleepy. A great way to achieve that is engaging in moderately intense exercise within the first two hours after waking up.

Doing that will not only make you more alert on a given day. After a couple of days, the signals from the increased temperature will shift your sleep-wake cycle forward, which will make you wake up earlier naturally. In a nutshell, if you’re a later chronotype, get physically active in the morning!

Pro tip: You can also shift your sleep-wake cycle to earlier in the day by directly exposing your body to cold or hot temperatures. The mechanisms are a bit counterintuitive, but very effective.

In the morning, a cold shower – ideally after your exercise session – will prompt your body to heat up as a reaction. This will make you alert, and shift your sleep-wake cycle forward. As a result, you will want to wake up 30 to 60 minutes earlier the following day.

A hot shower or sauna in the evening will have a similarly helpful effect. It will prompt your body to cool down as a reaction. This will make you sleepy, and also shift your sleep-wake cycle forward. Hence, you will want to go to sleep earlier the following day.