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Summary algorithms are metrics designed to aggregate and simplify multiple physiological and behavioral measurements into three easy-to-interpret outcomes. These scores are presented on a 0 to 100 scale, where 100 is the ‘best’ attainable score. By presenting data in a reader-friendly format, less experience and time is required to interpret each individual’s results, which helps both the end-user as well as any care-takers or data monitors. 

Below are the descriptions of each of three main summary scores presented by Biostrap: Activity, Recovery, and Sleep Scores.

Activity Score

Physical activity is a metric that has been shown to be correlated with numerous health outcomes and diseases. Activity is not exclusive to exercise bouts, and sedentary behavior has also been shown to be associated with health outcomes. 

Therefore, Biostrap calculates activity score using the distribution of activity over the course of a 24-hour window, emphasizing activity during 12 unique hours. Additionally, energy expenditure relative to the user’s goal contributes to the activity score. 

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Recovery Score

The recovery score is computed overnight, and is largely a function of the user’s resting heart rate and heart rate variability, compared to their rolling baseline values. Sleep parameters (sleep efficiency and sleep time as a percentage of goal sleep) make up a portion of the recovery score as well.

Sleep Score

Many aspects of a sleep session contribute to the summary Sleep Score. This score is a reflection of sleep duration and efficiency, relative to an individual’s sleep goal. A penalty system reduces the sleep score based on sleep disruptions and adverse physiological measures. The number of awakenings (weighted by severity), resting heart rate (relative to baseline), and low SpO2 readings (weighted by number and severity) all contribute to the sleep score penalty, reducing the overall score. 

Ready to start tracking your Sleep and Recovery? Join our Biostrap family and get started with our Recover Set.

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What is it

Sleep latency is the term given to describe how long it takes to fall asleep. Sleep latency can be highly variable due to behaviors prior to bedtime, such as alcohol, medications, exercise, diet, and blue light exposure, among others. However, tracking sleep latency can provide additional data that can reflect changes in health, behavior, and their interaction.

How is it measured

Sleep latency is measured in minutes from the time an individual attempts to fall asleep to the time when the individual enters sleep. While this can seem rather easy to qualitatively assess for an individual, tracking changes in physiological metrics through photoplethysmography (PPG) and accelerometry provides improved insight as individuals may have difficulty reporting the time of initial sleep onset. By tracking metrics such as heart rate, heart rate variability, respiration rate, and limb movements, a good understanding of bed time and onset of sleep can be made.

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Correlations to health conditions

The connection between sleep onset latency and clinical outcomes is less clear than that of total sleep time and deep sleep duration, however, there appears to be correlations between them. It is important to note that directionality and magnitude of latency may or may not have clinical relevance based on the situation that an individual is in. For example, long sleep latencies can be indicative of disorders, particularly related to stress or insomnia; however, shortening sleep latency may not reflect positive changes, as sleep latency is decreased by high amounts of sleep debt and may not reflect an overall positive change. Further, substances such as alcohol may reduce sleep latency but may lead to lesser quality of sleep.

Many of the correlations between latency and health are drawn in anxiety and depression. These psychological disorders are fairly common and are known to affect sleep and sleep latency. However, sleep latency is associated with total sleep duration reduction, which has a feed-forward effect on sleep, where less sleep causes more anxiety and depression. Thus, it can be important to monitor sleep latency changes to catch trends before they become problematic.

Normal or acceptable ranges

The National Sleep Foundation acknowledges up to 30 minutes of sleep latency, regardless of age, as appropriate. Sleep latency of 31-45 minutes is listed as ‘uncertain’, which could be due to individual trends. It stands to reason that very short sleep latency (<5 minutes) could indicate problems with fatigue and sleep deprivation, however, the research on normative values in this range are unclear.

Interpreting trends

Although the clinical recommendations remain unclear, tracking sleep latency could be good for most individuals. This metric, inversely associated with total sleep duration, could provide insight into behavioral changes and how they affect sleep architecture. Should sleep latency trend negatively for an individual, behavioral interventions could be suggested to correct sleep latency, and potentially increase total sleep duration. 

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What is it?

Sleep duration is simply the amount of time that an individual is asleep per night. Regardless of sleep stage, this measure has been shown to be an important factor to quantify, as it directly impacts physiological and psychological parameters in both the short and long term, impacting health, performance, and longevity.

What does it measure?

Sleep duration is the total sum of time spent asleep, regardless of sleep stage, excluding time spent awake while in bed. Using combinations of heart rate, heart rate variability, breathing, motion, and pulse waveform data, approximating sleep versus awake time is possible.

Biostrap uses inputs from all of the listed measurements to estimate light sleep, deep sleep, and time spent awake; therefore, the reflected sleep duration is the sum of light and deep sleep.

Correlation with health conditions

Adequate amounts of sleep have been tied to numerous health outcomes and remains a widely-studied topic. While sleep quality has been the focus of more recent research, the total sleep duration still remains a commonly reported metric and highly correlated with health outcomes.

Sleep is highly important to regulating biological processes, allowing for adaptation, recovery, and preparation. Many repair processes occur during sleep, with surges in growth hormones and reduction in stress hormones. Physiologically, increased sleep duration has been shown to reduce stress, improve cardiovascular markers (e.g. heart rate, heart rate variability, and arterial stiffness), reduce weight gain, improve immune function, and lower risk of all cause mortality and varying diseases. As such, sleep appears to improve physiological pathways robustly.

In addition to physiological effects, there are many cognitive benefits of increased sleep, including improved memory, problem solving, and reaction speed.

Normal or acceptable range

The American Academy of Sleep Medicine recommends at least 7 hours of sleep per night for adults aged 18-60 years, with the National Sleep Foundation recommending supplementing this recommendation with 7-9 hours of sleep per night for adults aged 65 years and older.

Biostrap records users’ sleep each night, and from this data, we can gather average values of distinct populations.

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Interpreting Trends

Considering the broad health implications associated with sleep duration, tracking sleep duration over time is recommended so an individual may notice trends in their behavior. This metric can be seen as a health behavior, and thus influences passively obtained physiology metrics. However, sleep duration can be monitored to see if other lifestyle factors or stressors are decreasing time asleep, which may be hard to notice in some individuals without measurements. Including sleep duration into longitudinal metrics can either explain or rule out other physiological trends, and therefore is included in Biostrap biometrics, allowing users and remote monitors to have a broader view of individual health.

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Respiratory rate is one of the main vital signs that measure a person’s health. Alongside body temperature, blood pressure, heart rate, respiratory rate is an essential measurement for determining well-being. 

Respiratory rate is the rate at which a full breathing cycle occurs, both inhalation and exhalation. While this is something that can be taken over by voluntary control, the majority of respiratory rate is an autonomic process, which occurs as a result of many inputs, including the respiratory center of the brain, which sends physiological sensory information throughout the body.

Age, weight and certain illnesses can all influence a person’s respiration rate. That’s why your normal respiratory rate may differ from the next person’s. If you learn to measure your respiratory rate, you’ll gain a better understanding of what is normal for you.

What Is a Normal Respiratory Rate?

The normal ranges for respiratory rate vary depending on a number of factors. For example, people who regularly practice deep breathing exercises, or those who play woodwind instruments, may take less breaths per minute, whereas people who are less physically fit may take more breaths per minute.

“We don’t really believe in comparing someone to a normal curve,” explains Kevin Longoria, MSc, a clinical exercise physiologist and the Chief Science Officer for Biostrap. “More importantly, we believe in comparing them to themself. We can see what someone’s normal respiratory rate may be and establish a trend. Then, you look at changes in the trend.” This allows you to determine what is a normal respiratory rate and what is abnormal for you as an individual.

In general, an abnormal respiratory rate is when the number of breaths per minute is under 12 or over 25 — but again, this can vary for every individual. A high respiratory rate means that the respiratory system is being overworked when it circulates oxygen through the blood and body. Conditions like asthma or sudden episodes, like an anxiety attack, can increase the number of times a person breathes per minute, resulting in a high respiratory rate.

In contrast, a child’s breathing rate would be different. “The normal respiratory rate changes significantly throughout the first several years of a child’s development,” says Longoria. For example, a baby up to 6-month old will usually have a breathing rate between 30 and 60 breaths per minute. A child between one and five will usually have a breathing rate between 20 and 30. By the time a child is 12, their breathing rate will usually be under 20.

According to Longoria, “abnormally high respiratory rates in children may be a sign of fever, dehydration, or conditions including bronchiolitis or pneumonia. Children may also experience rapid respiratory rates similar to adults due to other medical conditions including acidosis (with diabetes) and asthma.” And these are just a few of the factors that influence respiratory rate.

Factors That Influence Respiratory Rate

There are a number of common conditions that influence a person’s respiratory rate. For example, having anxiety and suffering from panic attacks can result in shallow breathing patterns and an acutely high respiratory rate for a short period of time (also referred to as hyperventilation).

“What’s really important when you look at respiratory rate is understanding autonomic control,” says Longoria. “When we look at the autonomic nervous system, it’s controlling all these voluntary processes like heart rate, respiratory rate, response to exercise, stress hormones, inflammatory processes — essentially things we don’t have to think about.” Factors such as exercise, stress, or changes in heart rate can influence respiratory rate involuntarily.

Shallow breaths or hyperventilation could be caused by the following conditions.

Lung and Airway Diseases

Lung diseases cause reduced oxygen uptake and prevent the lungs from working properly. For example, emphysema, severe/refractory asthma, and chronic bronchitis block a person’s airflow and contribute to an increasing sense of breathlessness.

These diseases are classified under the term Chronic Obstructive Pulmonary Disorder (COPD). Symptoms include shortness of breath, wheezing, chest tightness and chronic cough with and without mucus. COPD is primarily caused by smoking cigarettes but can also be associated with genetic conditions.

When it comes to factors that influence respiratory rate, “smoking is an obvious one,” notes Longoria. “If you’re smoking, then you’re getting more tar buildup and essentially causing what’s called a respiratory restriction.” Tar buildup in the lungs will damage your air sacs (alveoli) where gas diffusion takes place. “If we’re limiting the surface area of our lungs, our body will have to compensate with a higher respiratory rate.”

Having COPD is a risk indicator of cardiac arrest, in which the heart suddenly stops beating. Sudden cardiac arrest is a medical emergency that requires immediate treatment with a defibrillator. According to Harvard Medical School, more than 13 million Americans have COPD, and it tends to coexist with other conditions, like heart disease. Yet, many people are unaware of COPD.

Anyone who suspects they have COPD can be diagnosed by a spirometry test. This is a simple non-invasive process that evaluates your exhalation to see how well your lungs are working.

Sleep Disorders

Sleep disorders are another leading cause of airway obstruction and respiratory irregularities. During non-REM sleep, the part of our sleep cycle in which we spend 80% of the night, it’s normal to breathe slowly and steadily.

Breathing normally increases and decreases through different sleep stages, and the number of breaths a person takes will vary. However, having a sleep disorder can cause irregular sleep patterns and contribute to respiratory abnormalities. One example is sleep apnea, a common sleep disorder where a person stops breathing for as much as several seconds in their sleep. 

Heart Conditions

Heart problems can also affect a person’s respiratory rate. For example, atrial fibrillation (marked by irregular and rapid heart rate) can cause shortness of breath. When your heart beats irregularly due to atrial fibrillation, you may experience a tight chest and shortness of breath because the heart’s electrical signals don’t fire properly.

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Cardiovascular Fitness

Cardiovascular fitness is defined as the ability of your heart and lungs to deliver oxygen-rich blood to muscles throughout the body. “If you are frequently exercising, you tend to maintain better lung volume, resting lung capacity, and you have more arterial elasticity,” says Longoria. “Per breath, you’re consuming more oxygen than the next guy.” As a result, your respiratory rate will be lower because it will require fewer breaths to consume the same amount of oxygen.

How to Measure Respiratory Rate

Understanding your respiratory rate can make you more familiar with your body and help you monitor changes as you age. Plus, it can ensure that you recognize when it might be time to consult a medical professional about any changes to your body if changes to your respiratory rate occur.

Respiratory rate can be measured through photoplethysmography (PPG) by measuring the baseline shifts that occur with breathing. The baselines move up and down in an oscillatory pattern, which corresponds to the breath cycle.

A way to use PPG to measure is through a wearable that tracks vital biometrics for both sleep and fitness like Biostrap. “Biostrap is the only clinically-validated sensor system out there,” says Longoria. Wearable trackers can measure your oxygen saturation to indicate how much oxygen is pumping through the blood. It also helps you monitor the effectiveness of your workouts to better understand how blood oxygen levels could be increased through exercise, diet, deep breathing, and other healthy lifestyle changes.

Knowing Your Respiratory Rate

Your respiratory rate tells how much oxygen is flowing through your blood, but it also provides deeper clues to your health. For example, an abnormal respiratory rate can shed light on potential sleep disorders, lung disease, and heart conditions. “It’s an extremely important biometric,” Longoria stresses. “But it’s almost more important to know how and when you’re measuring it.”

Respiratory rate helps us understand changes in our own bodies, especially as we age or try out new approaches to fitness. Measuring your respiratory rate with a wearable that measures and tracks vital biometrics for both sleep and fitness can ensure that you’re always in tune with your body and the breath that keeps it alive.

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There are a number of metrics we can use to get a snapshot of our health and well-being. From blood pressure to heart rate, doctors and researchers are more interested in our physiological data than ever before. 

There is one marker for resilience and well-being that researchers have just begun to utilize over the past two decades. It’s called heart rate variability, or HRV. This metric, once measured primarily in athletes and those with abnormal heart rhythms, has since become a key piece of data for individuals wanting insight into the state of their physiology and nervous system.

So what exactly is heart rate variability? How do we measure it? And what can it tell us about our overall health? Let’s break down the intricacies of this emerging physiological measurement.

What Is Heart Rate Variability?

Heart rate variability, or HRV for short, is a measure of the time between each heartbeat. Heart rate by itself is the expression of how many contractions of the heart there are in a given unit of time; however, the rate itself is not constant. There is normal fluctuation of time between heartbeats, in a manner that speeds up and slows down heart rate. Therefore, HRV is a quantifiable measure that assesses these differences. 

Regulated by a fundamental part of our nervous system called the autonomic nervous system (ANS), HRV is one of many functions that occurs without us even having to think about it. HRV has been shown to correlate with emotional and physical stress, sleep, and disease making it a common method for assessing the overall physiological state and the rate of adaptation to stressors. 

Generally, the higher the HRV the better, as high stress and poorer health outcomes have been associated with low values of HRV.

How Do We Measure Heart Rate Variability?

HRV can be measured by an electrocardiogram (ECG) or photoplethysmography (PPG). By referencing a common point in the ECG or PPG waveform, the time between each heart beat can be recorded in milliseconds (ms). Collecting each beat-to-beat interval in ms allows us to compute HRV, most commonly reported as rMSSD (root mean square of successive differences). The rMSSD method of calculation takes each interval, squares the interval, takes the overall mean, and then the square root of that mean. More complex measures of HRV, including frequency domain analysis, can be used to get further information out of heart rate patterns and the state of one’s nervous system.

What Is a Normal Heart Rate Variability?

HRV has a large individual component that has yet to be understood clinically, and therefore is more often used to assess changes in health over time. HRV can fluctuate day-to-day based on exposure to stress, sleep quality, diet, exercise, and more. This leads to low repeatability, and therefore makes normative data difficult to collect. In general, younger individuals, males, and more active individuals tend to have higher heart rate variability, but the inter-subject variability tends to be too high to suggest proper normative ranges.

Focusing On Trends

As previously mentioned, HRV is difficult to interpret and generally nonspecific using data from a single spot check. However, since it is a dynamic measure that responds to various lifestyle factors, tracking HRV over time allows for non-invasive insight into changes in health status or efficacy of certain interventions. In general, since higher HRV is preferable, a greater ability to manage stress results in an increased HRV. The results of the studies demonstrating the relationship between stress and HRV suggest that interventions aimed at reducing mental and physical stress could increase HRV and minimize day-to-day fluctuations (coefficient of variation, CV%). The increase in HRV itself will not reduce risk and improve health over the long term, but rather, it reflects positive adaptations in an individual’s physiology.

For example, if we’re incorporating exercise or meditation into our daily routine, HRV should steadily increase. A downward trend, on the other hand, may be indicative of overtraining, poor sleep, illness, bad eating habits, increased exposure to stress, or failure to hydrate.

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What Factors Influence Heart Rate Variability?

Heart rate variability can be influenced by training, lifestyle, and biological factors.

Training factors that influence HRV include the intensity of a workout, exposure to unfamiliar stimuli, training load, and proper balance between rest days and training days. 

Lifestyle factors that influence HRV include diet and nutrition, stress, sleep habits, and alcohol consumption. Leading a healthy lifestyle that focuses on proper diet and physical fitness, while paying attention to mental health, is a valuable means of improving HRV.

Finally, biological factors such as age, gender, genetics, and health conditions can influence HRV as well. As we age, our HRV tends to decline, and men often have higher HRV than women. Genetics and health conditions such as cardiovascular disease are additional factors that may influence our heart’s ability to operate normally.

Should We Focus on Heart Rate Variability?

Measuring heart rate variability is a valuable form of analysis to monitor healthy individuals or to identify those who should seek improvement. The amount of information we get from HRV is making it a popular health data to assess physiological state, overall well-being and stress adaptation. You can track your HRV with clinical reliability with the Biostrap wrist-worn device and keep an eye on your nocturnal HRV as well as weekly, monthly and yearly trends.