Daylight Savings Stole Your Sleep? How Losing an Hour Affects Your Training

The clocks have jumped forward, and if you're feeling sluggish, you're not alone. Losing an hour might not seem like much, but for athletes who rely on quality sleep to train and recover, even small disruptions can take a toll.

We took a look at COROS user data to see how Daylight Saving Time (DST) impacts sleep, HRV, and running efficiency—and, more importantly, what you can do to stay on track. Here’s what we found, plus simple ways to adjust.

How Daylight Savings May Impact You

*The average night of sleep includes every Saturday night of 2025. DST sleep times refer to the night of March 8th into the morning of March 9th. Data is based on U.S. users only.

On average, COROS users slept in a little longer on the morning of March 9th, likely trying to make up for the lost hour overnight. While most users didn’t lose much sleep—just 8 minutes less on average—some may have fallen further behind. If you’re feeling the effects, here’s how to recover.

Dr. Peter Tierney, a health and performance researcher who has worked with many professional sports teams and performance organizations, explains the broader impact:

"We know that Daylight Savings Time can reduce sleep time between 40 - 63mins^(1,2). We also know that sleep for the week after (particularly Spring Forward) tends to be a little longer ⁽¹⁾ - so make sure you give yourself a larger sleep window this week. Spring Forward Daylight Savings Time has been reported to increase the incidence of road accidents, proposed to be from sleepiness⁽³⁾. Workplace injuries are also more common after DST - not only in terms of incidence, but also severity⁽²⁾. It has such a strong impact, that the American Academy of Sleep Medicine propose that DST is abolished to remain with a year-round fixed standard time⁽⁴⁾."

Understanding Your Sleep and Recovery

Given how DST can disrupt sleep and recovery, tracking your sleep is more valuable than ever. Monitoring your sleep duration, quality, and HRV can help you understand how schedule shifts affect your recovery. Recognizing these patterns allows you to make small but meaningful adjustments to improve your sleep and wake up feeling more refreshed. Here's what to look for:

• Sleep Duration & Stages – See how long you slept and how much time was spent Awake, and in Deep, Light, and REM sleep.
• Awake: Transition between sleep and consciousness.
• Light: Prepares body for deep sleep, aids recovery.
• Deep: Repairs muscles, strengthens memory, boosts immunity.
• REM: Enhances brain function, learning, and emotional processing.
• Sleep Quality – Sleep quality is your overall "sleep score," and is based on your time spent in each sleep stage compared to general recommendations. There are five possible sleep quality evaluations: Great, Good, Fair, Low, and Poor.

Where to Find It – Open the COROS app → Select Sleep from the homepage

• Heart Rate Variability (HRV) is a key marker of recovery. While daily fluctuations are normal, looking at trends over time can give you more actionable insights. A downward trend might signal overtraining or stress, while an upward trend suggests your body is reacting well to the impact of training and ready to take on more.
  

Where to Find It – Open the COROS app → Select Overnight HRV from the homepage → Toggle between Day, Week, and Month

"COROS Total Sleep Time (mins) is a valid and reliable way of tracking your sleep duration. The image below (COROS in Red) shows 28 days of sleep data compared to 2 other well known wearable devices that track sleep."
- Dr. Peter Tierney

Adjusting Your Training After Lost Sleep

Less sleep can mean slower recovery and higher fatigue. If your sleep data shows a dip in HRV or sleep quality, you can consider the following tweaks to your training to avoid burnout:

1. Ease into it – It takes a few days to adjust. Don’t push high-intensity workouts too soon, and add extra warm-up time if you're feeling sluggish.
2. Lower intensity if needed – Swap hard efforts for easier sessions until recovery improves.
3. Watch HRV trends – A drop means your body is under stress; adjust accordingly.
4. Zoom Out – acute sleep reduction can have negative effects, but try and approach this short reduction within the context of your monthly average." - says Tierney.

"Try to use a holistic approach when making decisions about training. If you see your sleep time is reduced, and this is coupled with feeling tired and changes in physiology (resting heart rate and heart rate variability), maybe consider reducing training intensity or volume. However, if your sleep time is reduced, but you feel great and your physiology is normal, then you can approach training with more confidence that you will perform and adapt well."

How to Make Up for Lost Sleep

Your COROS watch gives you more than just sleep duration—it shows you how well you’re sleeping and whether you're trending in the right direction. Here’s how to put that data to work:

✅ Use HRV Trends, Not Just One Day – HRV can fluctuate daily, but the long-term trend matters more. If your HRV has dropped since the time change, you may need to adjust your sleep timing and recovery methods.

✅ Prioritize Sleep Quality – If your Deep and REM sleep took a hit, improve your wind-down routine—reduce screen time, avoid caffeine late in the day, and stick to a consistent bedtime.

✅ Give Your Body Time – It can take a few days for your internal clock to fully adjust. Keep an eye on your sleep trends, and don’t stress over one rough night.

✅ Consider a Nap - if your total sleep time is reduced by DST, short naps can have positive benefits to energy and alertness, and help reduce the sleep debt you may accumulate. Make sure they are somewhere between 30-90 minutes, and aren't too late in the day (say after 3pm) so it doesn't affect the next nights sleep. (You can start a Timed Nap on your COROS watch).

Coaches Tip: Wearing your COROS watch to sleep can reveal insightful trends year-round. Learn more about the benefits of wearing your watch at night

References

 1.  de Lange MA, Richmond RC, Birnie K, Shapland CY, Tilling K, Davies NM. The effects of daylight saving time clock changes on accelerometer-measured sleep duration in the UK Biobank. J Sleep Res. 2024 Oct 21:e14335. doi: 10.1111/jsr.14335. Epub ahead of print. PMID: 39433070.

 2.  Barnes CM, Wagner DT. Changing to daylight saving time cuts into sleep and increases workplace injuries. J Appl Psychol. 2009 Sep;94(5):1305-17. doi: 10.1037/a0015320. PMID: 19702372.

 3.  Varughese J, Allen RP. Fatal accidents following changes in daylight savings time: the American experience. Sleep Med. 2001 Jan;2(1):31-36. doi: 10.1016/s1389-9457(00)00032-0. PMID: 11152980.

 4.  Rishi MA, Ahmed O, Barrantes Perez JH, Berneking M, Dombrowsky J, Flynn-Evans EE, Santiago V, Sullivan SS, Upender R, Yuen K, Abbasi-Feinberg F, Aurora RN, Carden KA, Kirsch DB, Kristo DA, Malhotra RK, Martin JL, Olson EJ, Ramar K, Rosen CL, Rowley JA, Shelgikar AV, Gurubhagavatula I. Daylight saving time: an American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2020 Oct 15;16(10):1781-1784. doi: 10.5664/jcsm.8780. PMID: 32844740; PMCID: PMC7954020.