Measuring Heart Rate Variability (HRV) for Athletes: Best Practices and Validated Consumer Products

Let’s dive into a topic that’s not just fascinating but also at the very core of our athletic endeavors—heart rate variability, or HRV. This critical measure offers profound insights into our cardiovascular and nervous systems, reflecting how well our bodies manage stress, recover from exercise, adapt to training and maintain homeostasis. In this article, you’ll discover the significance of heart rate variability (HRV) for athletes and why monitoring it can optimize your training and recovery. By the end, you’ll have a clear understanding of what HRV is, how to measure and interpret your data, and the impact of training on HRV, leaving you with actionable insights to enhance your athletic performance.

Understanding the Importance of HRV

Think of HRV as your body’s internal dashboard. A higher HRV suggests a robust ability to handle stress, indicating that we’ve recovered well and are ready to perform. Conversely, a lower HRV can signal over-training, stress, poor sleep, illness, and insufficient recovery. By monitoring HRV, athletes can fine-tune their training programs, ensuring they are not pushing too hard or resting too little, ultimately optimizing performance and improving long-term health.

What is Heart Rate Variability (HRV)?

Imagine listening to the sound of a heartbeat: boom, boom, boom. It seems like it’s beating at a consistent pace, right? Well, it turns out the heart is not like a metronome. Even at rest, a healthy heart is always either speeding up or slowing down. HRV is all about those little millisecond changes in the time between each heartbeat.

When you breathe, your heart and brain are constantly in sync, performing a little dance together. When you breathe in, your heart beats a bit faster; when you breathe out, it slows down. This heart-brain dance is known as respiratory sinus arrhythmia. It’s crucial because, throughout our day, we face many variations in physical and mental demands. We need a system that adapts quickly and effectively to these demands and helps us calm down when it’s time to relax or sleep.

So, HRV represents the variations in the time between heartbeats, and you can think of it as a measure of your body’s ability to adapt to stress and maintain a balanced system. These variations are influenced by the autonomic nervous system, which consists of the sympathetic (fight or flight) and parasympathetic (rest and digest) branches. A higher HRV indicates a more adaptable and responsive autonomic nervous system, whereas a lower HRV suggests reduced autonomic function. (Tiwari et al., 2021)

By keeping an eye on HRV, athletes can not only boost their performance but also promote long-term health and well-being!

HRV and Health Status

Higher HRV is associated with better cardiovascular health, resilience to stress, and lower mortality rates. (Jarczok, 2022). Conversely, lower HRV can indicate chronic stress, fatigue, and an increased risk of cardiovascular diseases and other health issues. (Tiwari et al., 2021, Arakaki et al, 2023) Clinical applications of HRV include its use in predicting the risk of arrhythmic events after heart attack, monitoring diabetic neuropathy, and assessing autonomic function in various other diseases. 

Taking it a step further, chronically decreased HRV is linked to reduced executive function, impaired decision-making, and emotional dysregulation. A recent meta-analysis of 32 studies involving over 38,000 participants revealed that lower HRV corresponds to a higher risk of death (Jarczok, 2022). Specifically, those with HRV in the lowest quartile faced a 56% increased risk of death. By monitoring HRV, we’re not just aiming for better performance; we’re striving for a healthier, more balanced, and potentially longer life.

Why Should Athletes Care About HRV?

For athletes, HRV is a valuable tool for monitoring training and recovery, and it is becoming a common practice. It helps in assessing how well the body is recovering from exercise and can guide adjustments in training intensity. High HRV typically indicates good recovery and readiness for intense training, while low HRV suggests that the body needs more rest and recovery. (Lundstrom et al., 2022, Addleman et al., 2024). There is even a potential for HRV monitoring to help aid in injury risk reduction. (Gisselman et al., 2015, Flatt et al., 2021) Here are some suggested best practices for measuring HRV and the validated consumer products that athletes can rely on.

Best Practices for Athletes to Measure HRV

Time of Measurement

HRV measurements can vary depending on the time of day. (Lundstrom et al., 2023) Long-term data indicates that HRV is highest during sleep (Yamasaki et al., 1996), while the lowest levels are typically recorded in the late morning and early afternoon (Jarczok et al., 2019). To minimize time-of-day related variability, it is generally recommended to take HRV readings either overnight or consistently at a standardized time, such as immediately upon waking. Research has shown strong correlations between morning and nocturnal HRV readings in young athletes (Mishica et al., 2022), indicating that the time of day for recording HRV is more flexible for this group. However, adults and older athletes have less flexibility in this regard, requiring more consistency in the timing of their HRV measurements to ensure reliability.

Consistency

It is crucial to maintain consistency in measurement. This means using the same device and following the same routine every day. Consistent conditions ensure that the data is comparable over time.

Duration of Recording

A short-term recording of around 5 minutes is commonly recommended for HRV measurements. For those looking for even shorter durations, one-minute ultra-short-term measurements are shown to be reliable. (Lundstrom et al., 2023). Ultra-short recordings of 10-30 second durations significantly decreased reliability and are not typically used in athletes. (Esco et al., 2014)

Body Position

The body position during measurement significantly impacts HRV values. The highest HRV values are generally observed when lying down, with a reduction in the seated position and an even further decrease when standing. (Lundstrom et al., 2023) Consistency in body position is essential for accurate tracking.

Response to Training

It is generally accepted that athletes have a higher HRV than sedentary individuals (Dong et al., 2016, Mourot et al., 2004); however, athletes often exhibit varied HRV responses to training. (Addleman et al., 2024). This makes longitudinal tracking vital for understanding individual patterns and responses. Comparing an athlete’s 7-day rolling averages of HRV to daily values likely offers a more meaningful context for understanding HRV changes than relying solely on daily measurements.(Addleman et al., 2024)

HRV has been linked to improvements in training adaptations such as VO2 max and running performance in endurance athletes. (Addleman et al., 2024). Additionally, research suggests that higher baseline HRV may indicate advanced training status or training age, while a lower HRV or slower return to baseline HRV might be associated with lower training age and reduced adaptability to training. (Seiler et al., 2007, Flatt et al., 2022)

Based on the article “Heart Rate Variability Applications in Strength and Conditioning: A Narrative Review,” acute, transient reductions in HRV have been noted in response to both aerobic and strength training. Chronic adaptations, however, lead to increased baseline HRV, reflecting better autonomic balance and cardiovascular efficiency. Advanced endurance athletes typically experience increases in HRV post-training with quicker returns to baseline, even with increased training loads, due to their higher fitness levels and training age. In contrast, lower-level endurance athletes often see temporary decreases in HRV following training or load increases, indicating higher stress and lower adaptability.

Acute, transient reductions in HRV have been observed following increases in resistance training load, volume, and intensity. The recovery time for HRV to return to baseline varies based on the individual or sport, ranging from as quickly as one hour post-training to several days. (Grässler et al., 2021) A recent review by Grässler et al. (2021) examined six studies on the relationship between HRV and resistance training. The authors found significant improvements in HRV in four studies, while the remaining two showed no clear results.

It is important to note that the body of scientific evidence evaluating the relationship between HRV and resistance training adaptations is still in its infancy, especially when compared to the extensive research on HRV and cardiovascular endurance training. (Addleman et al., 2024) Considering the totality of available evidence, it seems that high-intensity or novel training sessions can cause transient HRV reductions, particularly when deviating significantly from an athlete’s baseline. This may occur with cardiovascular endurance or resistance training. This pattern parallels findings in exercise immunology, where higher training intensities correlate with transient immune disturbances and reduced immunity. While a direct causal link between HRV and immune function isn’t established, their correlation suggests interconnected autonomic and immune responses to training stress. (Thayer et al., 2012, Thanou et al., 2016)

The transient reductions in HRV following high intensity exercises sessions is likely a normal response to training and may reflect the early stages of adaptation. However, athletes should be aware that the combination of a reduced HRV and a high acute–chronic workload ratio may be associated with an increased risk of overuse injury. (Addleman et al., 2024, Wiliams et al., 2017)

HRV Response to Other Factors

Numerous factors can affect an individual’s heart rate variability (HRV) baseline and cause deviations from it. These include aging, male sex, higher BMI, poor sleep quality and duration, stress and anticipation of stressful events, alcohol and nicotine use, dehydration, acute illness, symptoms following vaccination, acute and chronic pain, and recovery from concussions. Additionally, travel, training camps, and various medications such as beta-blockers, ACE inhibitors, contraceptives, and antidepressants can all influence HRV. (Addleman et al., 2024)

Tools and Techniques

Monitoring Tools: The gold standard for HRV monitoring is the electrocardiogram (ECG). However, other tools like chest strap heart rate monitors and photoplethysmography (PPG) devices (e.g., wrist and finger-worn devices) are also widely used due to their convenience and reliability.

HRV Data and Reliable Consumer Products 

For athletes looking to incorporate HRV monitoring into their routine, several consumer products have been validated against the gold standard ECG. If you are going to measure your HRV, it’s important to understand the data your device is giving you! Below you will find two paragraphs describing the two most common data points provided by these devices, followed by a list of validated consumer products to consider. I have provided a layman’s version and a more robust explanation for these data. Later in the article, I also provide tables where you can reference normal data values by age, sex and athletic status!

Layman’s Terms for HRV Data

SDNN is like checking how much the drummer changes the speed of their drumming over a long time, like during a whole concert. It looks at the overall rhythm and sees how much it speeds up or slows down. If the drummer sometimes speeds up and sometimes slows down a lot, the SDNN number will be bigger.

RMSSD is like checking the drummer’s changes in speed between each beat, but only over a short time, like just a few minutes. It looks at the small, quick changes. If the drummer’s beat changes a lot from one beat to the next, the RMSSD number will be bigger.

So, SDNN checks the overall, long-term changes in the heartbeat, while RMSSD looks at the quick, short-term changes between each beat.

Scientific Terms

HRV, or Heart Rate Variability, is a quantitative marker of autonomic nervous system activity and cardiac function. RMSSD (Root Mean Square of Successive Differences) is a time-domain measure that calculates the square root of the mean of the squares of the differences between successive NN (normal-to-normal) intervals. RMSSD is particularly sensitive to high-frequency variations in heart rate, making it a robust indicator of parasympathetic (vagal) activity. SDNN (Standard Deviation of NN intervals) is another time-domain measure that represents the standard deviation of all NN intervals recorded over a given period, typically 24 hours. SDNN reflects overall HRV and is influenced by both sympathetic and parasympathetic nervous system activity. While RMSSD provides insights into short-term changes and parasympathetic function, SDNN offers a comprehensive view of overall autonomic balance and long-term variability. Both metrics are helpful for assessing cardiac autonomic regulation and overall cardiovascular health.

Consumer Product types for Measuring HRV

  1. Chest Strap Heart Rate Monitors:

These devices are highly reliable for HRV measurements and are commonly used by athletes for their accuracy and convenience.

  1. Photoplethysmography (PPG) Devices:

Wrist or finger-worn Devices: These are relatively accurate at rest. However, their accuracy can vary during vigorous exercise, depending on the model and type of activity.

In general, chest strap device seem to be the most reliable and valid, followed by PPG devices (watches and rings).

Consumer-grade product list

Here you can find a list of validated consumer-grade tools for measuring HRV. I have also provide which HRV metric (SDNN or RMSSD) these products measure so you an reference these in the tables at the end of the article. If you are planning to purchase a product and would like to support this blog, please consider using the affiliate links here. As an Amazon Associate I earn from qualifying purchases.

Polar H10 (Chest strap)

(payed affiliate link)

(Hinde et al., 2021) compared the Polar H10 to a three-lead ECG Holter monitor and found a high correlation (r = 0.997) between methods, indicating the Polar H10’s accuracy in measuring HRV​. This chest strap will pair with another watch or third-party app and can provide both SDNN or RMSSD HRV values.

Apple Watch

(payed affiliate link)

The Apple Watch has not been validated against ECG for HRV measurements in a direct, peer-reviewed comparison study. The study often referenced, which validated the Apple Watch for HRV, compared it against the Polar H7 rather than a standard ECG. (Hernando et al., 2018). This study found that while the Apple Watch can reliably measure HRV and detect stress-induced changes, it was not directly validated against ECG​.

However, the Apple Watch has been validated for heart rate and rhythm detection against ECG in other contexts, such as atrial fibrillation detection, showing high accuracy in those studies (Perez et al., 2019)​. These validations primarily focus on the heart rate and rhythm detection features, including the single-lead ECG functionality of newer Apple Watch models, rather than HRV specifically. The apple watch will provide RMSSD HRV data.

WHOOP

(payed affiliate link)

The WHOOP Strap has been evaluated in multiple studies for its accuracy in measuring HRV compared to ECG. However, these studies sometimes present conflicting results due to differences in study design, population, and methodology.

WHOOP should be considered reliable for heart rate measurement due to its consistent accuracy. However, its HRV measurements, especially during sleep, should be interpreted with caution due to potential biases and limits of agreement. The sponsorship of key researchers by WHOOP Inc. introduces a conflict of interest that readers should we aware of. Therefore, independent validations are recommended for a more objective assessment of WHOOP’s HRV accuracy. After reviewing the available evidence(Bellenger et al., 2021, Hinde et al., 2021, Miller et al., 2022) and considering the potential conflicts of interest, it is clear that while WHOOP shows promise, there are limitations and biases that must be accounted for in HRV measurement contexts. Whoop will provide RMSSD HRV data.

Oura Ring

(payed affiliate link)

Cao et al., 2022 assessed the accuracy of nocturnal heart rate and HRV parameters collected by the Oura Ring against a medical-grade chest ECG monitor. The Oura Ring showed high positive correlations and low error variances for HRV, specifically RMSSD. 

Stone et al., 2021 confirmed that the Oura Ring’s sensor matched the performance of clinical-grade ECG and outperformed other similar sensors in measuring HRV. The study highlighted the ring’s accuracy in measuring HRV, with a high degree of concordance with ECG.

These data suggest the Oura Ring provides reliable nocturnal HRV measurements comparable to ECG​. The Oura ring can provide both SDNN or RMSSD HRV values.

Normative HRV Values

Below I have provided tables where you can reference normative data values by age, sex and athletic status! Normative HRV data refers to the standard or typical values of HRV derived from studying a specific group of people (healthy women, college athletes, etc). These norms help provide a benchmark for interpreting your individual HRV measurements. Don’t be overwhelmed by the amount of data here. Most of you will just want to reference the “SDNN” or “RMSSD” values.

Final Thoughts

By adhering to best practices and utilizing validated consumer products, athletes can effectively monitor their HRV. This enables them to fine-tune their training, optimize recovery, and ultimately enhance their overall performance. I hope you found this article helpful. Please share this knowledge with anyone you think will benefit from it.

Adolescent Non-athlete (Sharma et al., 2015)

Female

Male

Adolescent athlete (Sharma et al., 2015)

Female

Male

Adults (Normal, healthy, *minimum age 40) (Nunan et al., 2010) *older age of subjects likely explains lower HRV values)

Adult athletes (Berkoff., 2007)

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