Is monitoring sleep time worthwhile

As an avid cyclist and an occasional insomniac, I have developed the habit of checking my sleep data first thing in the morning.

Take today, for instance. Within seconds, the data from my Garmin watch transferred to my phone, showing that I had slept for eight hours and 32 minutes.

Out of this, 39 minutes were categorized as 'deep' sleep, five minutes as 'light,' and two hours and 38 minutes as REM sleep.

When I scrolled down to see my 'sleep score,' which ranks sleep quality from zero to 100, I received a score of 82 ('good'), indicating that I was well-rested for the intense interval training I planned later.

Obsessing over this data has become a tough habit to break.

I am not alone in this. Cyclists are accustomed to coming home, unclipping their pedals, and analyzing their ride data.

Many of us are also tracking what happens during our sleep, using wearables that monitor sleep and other recovery metrics like heart rate (HR) and heart rate variability (HRV), which measures the time differences between heartbeats.

The goal is to collect data on both how hard we’re pushing ourselves on the bike and how well our bodies are recovering afterward—guiding our workload for the following day.

Companies that produce these trackers are keen to connect with the cycling community.

Whoop sponsors the EF Education-EasyPost team and world champion Mathieu van der Poel, while Ultrahuman supplies the Air ring worn by Tadej Pogačar and his UAE Team Emirates teammates.

At the upcoming Tour de France, EF will also use the Eight Sleep Pod, a cooling mattress topper, on riders' beds to lower body temperature and collect sleep data.

While sleep data can be useful for micromanaging professional riders’ health, can it also benefit everyday cyclists like you and me?

These trackers claim to measure sleep quality, quantify 'readiness' to ride, and alert us to potential illnesses, but are they accurate?

Furthermore, could too much information add to mental stress, making it harder to sleep?

To answer these questions, I decided to test a Whoop band and Ultrahuman’s Air ring.

Before jumping into the testing phase, let's explore how these wearables function. Sleep involves various physiological changes, including brain activity, heart rate, blood pressure, body temperature, respiration, eye movement, and muscle tone.

The gold standard for measuring sleep is the polysomnographic (PSG) laboratory test, where a team of professionals uses electrodes to capture these changes.

In contrast, wearables detect some of these changes, such as HR and HRV, by shining a light through the skin to measure blood flow changes.

They also monitor temperature and movement using accelerometers, although the latter can be unreliable since some people move a lot in their sleep while others lie still but awake.

Sleep experts generally agree that wearables are reasonably accurate in determining whether someone is asleep or awake.

However, they are less effective at measuring the duration of different sleep stages.

As cyclists, we are particularly interested in these stages because our bodies repair themselves during the 'deep' phase of each sleep cycle.

During deep sleep, muscles repair, and human growth hormone (HGH) is secreted, aiding fat burning and tissue growth.

The REM phase, on the other hand, helps us recover mentally by consolidating learning and memories and reducing levels of noradrenaline, a stress-related hormone.

"Not all current sleep measurement technologies are valid or reliable," says Dr. Sarah Gilchrist, who holds a doctorate in sleep and athletic performance.

Gilchrist advises cyclists to avoid becoming overly focused on gathering sleep data and instead pay attention to whether they feel "alert, refreshed, and productive" during the day.

If not, they should establish a routine of going to bed earlier. It's that simple.

Research supports Gilchrist's skepticism about the accuracy of trackers in measuring sleep stages.

A 2023 study evaluated four commercial sleep-tracking devices—Fitbit, Garmin Vivosmart 4, Oura Ring, and Withings Mat—by comparing them with research-grade actigraphy (a wristwatch-like device that monitors motion) and polysomnography.

Scientists observed 53 young adults in the lab for one night. Except for the Garmin Vivosmart, all devices were found to estimate total sleep time comparably to research-grade actigraphy and were deemed "reliable and convenient" compared to lab sleep tests.

In other words, most wearables performed well in detecting and measuring sleep quantity, which is crucial since people often mistake time spent in bed for time spent sleeping.

Everyone should aim for seven to nine hours of sleep per night, even longer if they've had an exceptionally tiring day on the bike.

However, the devices were much less accurate in measuring the different phases of sleep.

The study highlighted that distinguishing between light and deep sleep was particularly difficult for sleep-tracking devices, although it acknowledged that newer models are improving.

The conclusion noted that only 5% of consumer sleep-tracking technologies have been formally evaluated, calling for further enhancements in reliability and accuracy.

There is also a lack of transparency regarding how these devices function, with their patented, secret algorithms generating 'scores' that scientists cannot thoroughly investigate.

A consensus from a 2020 expert panel of sleep researchers found insufficient evidence to support sleep staging in wearable devices and raised concerns about the psychological impact on athletes of seeing low sleep scores, especially before competitions.

I decided to test this for myself by using a Whoop band and an Ultrahuman Air ring separately, each for a week, while keeping my Garmin watch on for comparative data.

Starting with the Whoop band, I appreciated its screen-less design, which made it easy to forget I was wearing it while its data synced with an app.

Whoop focuses on three main areas: sleep, recovery, and strain. The sleep data it provided was much more detailed than what my Garmin watch offered.

Whoop not only told me how much sleep I got but also broke it down into percentages of deep and REM sleep—providing insights different from my Garmin watch and leaving me unsure which was more accurate.

The Garmin and Whoop also disagreed on sleep duration, with Garmin showing an average of seven hours and 13 minutes, whereas Whoop recorded only six hours and 47 minutes.

I also monitored my heart rate variability (HRV) through the Whoop app.

One morning, my HRV dropped from 67 to 40, and later that day, I started feeling unwell.

While HRV monitoring was helpful in this instance, I'd caution against overanalyzing it due to its fluctuations.

The final metric in the Whoop app, strain, measures your workouts and advises on the corresponding hours of sleep needed and activity levels for the next day.

After a 107km ride with 1,007m of climbing, my band suggested I needed 9.5 hours of sleep.

The Whoop device is free, but it requires a monthly (£27) or annual (£229) subscription. Although the data was clear and easy to track, I'd hesitate to pay for the subscription given the availability of other devices that offer sleep data without a recurring fee.

Ultrahuman sent me a ring-sizer kit, and after choosing my size and color, I downloaded its app. The concept is similar to Whoop's, as the Air ring records HR and HRV and tracks sleep.

After one night with the ring, I downloaded a 'sleep index' score, which included factors like time, body temperature, restfulness, and efficiency.

Like the Whoop band, the Air ring recorded 20-30 minutes less sleep than my Garmin watch, suggesting that the Garmin might be overestimating sleep duration. Surprisingly, the Air ring consistently showed a much lower HRV than the Whoop band, even on good sleep nights.

While my HRV was in the mid to high 60s on Whoop, it averaged 44 on the Air ring app.

The Air ring app offered advice based on my circadian rhythm, such as when to get sunlight and reminders to move if I was stationary for too long.

It also provided stress reduction tips through yoga videos and breathing exercises, along with 'sleep stories' similar to those from apps like Headspace and Calm.

Unlike the Whoop band, the Air ring did not give guidance on how my workouts affected my recovery. The Air ring is priced at £329 as a one-time purchase.

Orla Walsh's Wearable Device Alerted Her to Illness

Track cyclist Orla Walsh, an 11-time Irish national champion, has been using a Whoop band since 2019 to track her sleep and recovery.

Walsh relies on her sleep scores and adjusts or switches her training sessions based on the data.

When adjustments aren’t possible, she tries to manage fatigue by staying hydrated and maintaining proper nutrition. However, the 25-year-old sometimes questions the data's accuracy.

“The recovery score might show I’m in the green, but neurologically, I feel exhausted as a sprinter,” she explains. “Heart rate data struggles to accurately measure the effort involved in sprinting or weightlifting since there's minimal cardio."

Using the app's diary tool, Walsh discovered her caffeine intake was affecting her sleep, leading her to eliminate coffee from her diet.

She also uses the Whoop to detect signs of illness. One symptomless morning in 2021, she noticed a significant increase in her respiratory rate from her usual 15.8 rpm to 17.9 rpm, her average heart rate climbed nearly 10 bpm, and her heart rate variability dropped from 57 to 40.

Heeding these warning signs, she skipped the gym and took a Covid test, which came back positive.

Key Takeaways

After testing two leading sleep trackers, would I continue using one long-term? In short, no, but I did learn two important lessons.

First, I found out I sleep less than I thought—about an hour less each night. Second, behaviors negatively affecting my sleep were effectively identified.

For example, after logging entries in Whoop’s journal section, I realized my mid-afternoon coffee was probably harming my sleep.

This aligns with Gilchrist’s view that sleep trackers can help “monitor changes in sleep quantity by promoting behavioral changes.”

Did a poor sleep score stop me from riding? No, especially if the weather was nice.

However, on days with good sleep scores, I felt more confident to push myself harder.

Personally, I found the amount of data overwhelming, and being told you’ve slept poorly when you’re already anxious about sleep is, at best, unhelpful.

If you suffer from insomnia, consider other interventions. Gilchrist suggests using the Epworth Sleepiness Scale to identify behaviors causing sleep issues.

If you generally sleep well and have the time to analyze the data, a sleep tracker could be beneficial or at least interesting, shedding light on your nighttime activities.

Source: cyclingweekly

The opinions shared in the GymNation blog articles are solely those of the respective authors and may not represent the perspectives of GymNation or any member of the GymNation team.