What can I measure with the morning check-in?
Visible’s morning check-in uses your device’s camera to measure some of your body’s key signals. It does this by capturing small changes in the color of your skin, which it uses to measure your pulse.
Your heartbeat can reveal some valuable insights about your body including heart rate variability, resting heart rate and your morning stability score. This page explains the relevance, meaning and accuracy of those metrics.
Important note: Visible is not a substitute for the advice of a medical professional based on your personal circumstances. You should always consult a doctor before making any medical decisions.
Heart Rate Variability (HRV)
What is HRV?
Heart Rate Variability (HRV) is a measurement of the variation in time between your heartbeats. More than 55,000 studies show that it reflects the activity of your body’s stress response and recovery systems.
To understand HRV, it’s important to know that the human heart is not a metronome. A heart rate of 60 beats per minute suggests one beat per second; in reality, there are millisecond variations between successive heartbeats. Some beats are more like 0.9 seconds apart while others are more like 1.2 seconds apart.
Oddly enough, the healthiest people don’t have more steady, consistent heartbeats. Instead, their hearts react and recover from stressors and soothers quickly, causing heartbeat intervals to vary. Because of that, a high HRV score indicates better health.
Why is HRV relevant to me?
Unsurprisingly, research has shown that HRV is lower in people living with both Long Covid and ME/CFS. For this reason, you might find it helpful to track over time as an indicator of your wellbeing. Generally speaking, a trend towards increasing HRV is a good signal of improving overall health.
Tracking HRV may also help you to better manage your illness. Measuring it as part of the morning check-in creates a powerful feedback loop that can help you understand what changes (whether it’s pacing, medication or something else) might be improving your health.
What is a normal HRV?
Heart rate variability is based on individual circumstances. Many factors such as the nature of your illness and its severity, your recent activity levels and even your emotional state can affect it. For this reason we always emphasize looking at long-term trends in HRV over comparing yourself to others.
How do we detect your HRV with your phone camera?
The extraction of heart rate variability (HRV) from camera sensor data is known as photoplethysmography (PPG) and has been studied and researched extensively.
PPG is an optical method used to measure small blood volume change in body tissues, such as the finger. As the heart pumps blood, the volume of blood in the arteries and capillaries changes by a small amount in sync with your heartbeat. This change leads to small changes in skin color.
By placing your finger on the camera lens, the camera sensor is able to pick up small changes in skin color, and therefore determine the timing of the intervals between your heartbeats.
How do we calculate your HRV?
To calculate HRV from your heartbeats we apply a Root Mean Square of Successive Differences (“RMSSD”) calculation to the beat-to-beat intervals. RMSSD is the industry standard time measurement for detecting Autonomic Nervous System activity in short-term measurements.
Next, we apply a natural log (ln) to the RMSSD values. RMSSD values do not chart in a linear fashion, so it can be difficult to make sense of the magnitude of changes in RMSSD as it rises and falls. By applying a natural log (ln) to RMSSD, we can produce a number that is more linearly distributed.
Finally, we expand the ln(RMSSD) to create a 0 to 100 score, which is the one you’ll see in the Visible app. The ln(RMSSD) value typically ranges from 0 to 6.5. Using over 6,000,000 readings from the EliteHRV database, we have been able to sift out anomalous readings and create a more precise scale where every reading fits in a larger range.
This means that the value you see in Visible might be slightly different to the one you see in other apps. But you should find that over time, the 0 to 100 scale makes it easier to compare your HRV between days, and spot trends in your HRV.
Morning stability score
What is the morning stability score?
The morning stability score is a score from 1-5, which compares your HRV and resting heart rate values to your recent past. It determines whether you are in a similar state or swinging widely outside of your norm.
It takes at least 4 morning check-ins on four different days for us to identify your recent baseline, and therefore calculate your score. If you don’t complete a check-in for 10 days, you’ll need to complete these readings over again.
The interpretation of your score offered by Visible depends on its range, as follows:
The morning stability score is highly individualised, so you may score similarly to other/ Visible users even if your HRV or resting heart rate is in fact much higher or lower than theirs.
Why is morning stability relevant to me?
Research has shown that low and unstable HRV can be a reliable predictor of fatigue severity. For this reason, you may find that the morning stability score correlates with your experience of symptoms. In addition you might find it helpful when pacing; for example on days with a lower stability score you may decide to take things more slowly.
Important note: the morning stability score is not intended to substitute professional medical advice, diagnosis, or treatment and does not guarantee an accurate evaluation of your health or wellbeing.
What if the morning stability score doesn’t feel right?
At Visible, one of our core beliefs is that you know your body best.
Your morning stability score may be a useful indication that your body is under more stress than you realize, for example in advance of a crash or flare up. It’s based on data, but it’s not always right. It’s also no substitute for your own knowledge of your condition, and what’s best for you. That’s why we’ll only ever give you insights, not instruction when it comes to your illness.