With daylight saving time happening in North America this weekend it’s a clear signal that winter is approaching and there are fewer evening daylight hours for training. Aside from the fact we’ll gain an extra hour of sleep, what happens to our body around the semi-annual time change—and how can we mitigate its impact?
Chronobiology is the study of internal physiological clocks, which fluctuates over time (Cheung and Ainslie 2022). We often equate chronobiology with circadian rhythms, or changes that cycle over a 24-hour time frame. However, humans experience many other rhythms, ranging from ultradian (e.g., on the scale of hours, such as appetite and feeding cycles) to infadian (e.g., over more than a day, such as the menstrual cycle).
When it comes to time change, there is some analog to traveling across time zones, so daylight saving time in the fall can be likened to traveling one time zone west. In a study on elite athletes flying either westward (a shift of six hours) or eastward (a shift of eight hours), jetlag symptoms were roughly similar in lasting five to seven days, while subjective training performance appeared worse in intensity and duration with westward travel (Lemmer et al. 2002). The big difference is that time change is a circadian clock shift without the associated fatigue of travel (e.g., sitting in a car all day or flying). Indeed, those are two separate factors contributing to long-distance travel or jetlag that are relatively difficult to separate, though one little-used way to study travel fatigue by itself is to conduct long-distance travel north-south or vice versa.
Compared to transcontinental travel, the shift of one hour caused by daylight saving time is considered quite minor compared to shifts of three hours or more (Janse van Rensburg et al. 2021). Especially without travel fatigue and with favoring additional sleep, it is likely that there is not going to be a major impact on your training capacity or performance from fall time change. Worse case is that you might show up for your workout or race early! This is in sharp contrast to spring time change where we move our clocks ahead by an hour and often lose an hour of sleep. There, the transition can lead to worse driving simulator performance (Orsini et al. 2022), though epidemiological studies on whether that results in greater traffic accidents or hospital trauma admissions is equivocal (Teke et al. 2021).
How to make daylight saving time work for you
The smartest plan for fall time change is to take advantage of that extra hour of sleep. There’s nothing extra that you need to plan for—just treat it as a normal day and go to bed and wake up at the same time. Do not sabotage your chance for recovery by treating it as a day where you can wake up earlier and get in a longer ride.
Getting beyond the single day of time change caused by daylight saving time, try a simple experiment and see how getting more sleep helps your recovery and ability to train. First, set yourself the challenge of getting just 30 minutes extra sleep the day before and after the time change. That’s two extra hours (30 minutes + 60 minutes + 30 minutes) of sleep over three days. The second step is to not do additional training beyond your normal load so that your training stress is constant.
If you’re using a recovery or sleep tracker, see how your recovery metrics like heart rate variability change over those three days. Whether you use a tracker or not, write down how you feel over the course of those three days, from things like your mood to how you feel upon waking and during training. I’m going to guess that you’ll be pleasantly surprised by how much better and more positive you will feel, and hopefully this will motivate you to make small changes that can have a major improvement on your sleep quantity and quality all year round.
Cheung SS, Ainslie PN (2022) Advanced environmental exercise physiology, Second edition. Human Kinetics, Inc, Champaign, USA. ISBN 978-1-4925-9398-0
Janse van Rensburg DC, Jansen van Rensburg A, Fowler PM, et al (2021) Managing Travel Fatigue and Jet Lag in Athletes: A Review and Consensus Statement. Sports Med 51:2029–2050. https://doi.org/10.1007/s40279-021-01502-0
Lemmer B, Kern R-I, Nold G, Lohrer H (2002) Jet Lag in Athletes After Eastward and Westward Time-Zone Transition. Chronobiol Int 19:743–764. https://doi.org/10.1081/CBI-120005391
Maughan RJ, Zerguini Y, Chalabi H, Dvorak J (2012) Achieving optimum sports performance during Ramadan: some practical recommendations. J Sports Sci 30 Suppl 1:S109-117. https://doi.org/10.1080/02640414.2012.696205
Orsini F, Zarantonello L, Costa R, et al (2022) Driving simulator performance worsens after the Spring transition to Daylight Saving Time. iScience 25:104666. https://doi.org/10.1016/j.isci.2022.104666
Teke C, Kurtoğlu Çelik G, Yıldırım Ç, et al (2021) Assessment of the number of admissions for road traffic collisions and severity of injury in daylight saving time and permanent daylight saving time periods. Int J Clin Pract 75:. https://doi.org/10.1111/ijcp.14798