Diving into Heart Rate Variability

First, let me make the boldest statement on Earth.

If you want to major in Exercise Science, I don’t think there is a better school in America than Lenoir-Rhyne University. Dr. Alex Koch and Dr. Keith Leiting, the two lead professors at Lenoir-Rhyne University, love the strength world and have spent their lives engulfed in the research.

This week during my summer school class we discussed Heart Rate Variability (HRV). I was excited to dive into this topic because I haven’t looked at HRV in any depth. Plus, I am considering using HRV as one of the daily testers for my weightlifters.

Our guest lecturer for the week was Dr. Mike Landram. Dr. Landram was a student of Dr. Koch’s at Truman State circa 2005, and went on the earn his M.S. in Exercise Science from Appalachian State University. Then he made us all jealous by earning his PhD from the University of Rome in Rome, Italy. Can you imagine how awesome that was? His lecture was fantastic and truly educational.

The article we looked at was an in-depth meta analysis that looked at all the different frequencies of HRV, the suggested indicators of each frequency, and how true each indicator actually is. To say I learned a lot is the understatement of the year. First, here’s the article I am referencing for the most part:

“Heart rate variability”
Harald M. Stauss
Am J Physiol Regul Integr Comp Physiol 285: R927–R931, 2003; 10.1152/ajpregu.00452.2003.
Department of Exercise Science, University of Iowa, Iowa City, Iowa 52242
AJP-Regul Integr Comp Physiol • VOL 285 • NOVEMBER 2003 • www.ajpregu.org

Conclusions

Now let’s look at what I learned. The first thing I want you guys to understand is the difference between the time domain and the frequency domain when it comes to measuring and analyzing HRV. First, the most common is the time domain. The time domain is a simple look at a given amount of time (for example, four minutes), the time between the individual beats, and the amount of variance of the beat-to-beat times. There are a few different formulas to measure the variance in the heartbeats with rMSSD being one of the popular ones.

The time domain is the one we hear about the most. It’s a simple look at HRV during a short interval. This will give you an idea of what’s going on, but there are too many variables that can affect HRV during a four-minute cycle. Remember the cardiovascular system is directly connected to the brain. The heart is one of the main ways that the autonomic nervous system maintains homeostasis. The brain is continually receiving and discerning information. For example, when you are in a bad situation, adrenaline is pumped into the blood to give you the strength to handle the stressors. The adrenaline dump increases the heart rate. The problem is that all stress causes this to happen, so stress at home and at work will cause this system to overwork. All of this is from the sympathetic nervous system, which is like the turbo booster portion of the ANS. The parasympathetic system works to counter the heart rate increase.

The point is there are a lot of variables that could possibly shake up one’s heart rate variability. However, the frequency domain looks at HRV over a longer period. The frequency domain is looking at the relative occurrence of particular frequencies: high frequency, low frequency, very low frequency, and ultra low frequency. The amount that each occurs can help determine parasympathetic vs sympathetic nerve activity. However, this method isn’t always perfect. With frequency a mathematical equation is used to determine the waves within the waves so to say. There are variations that occur at short cycles, and variations that occur over several hours. With frequency, the measurement is in hertz, which is a way of looking at whatever is occurring at a per second time interval. With HRV, it’s normally a low hertz because nothing is entirely happening in one second unless you are overly excited.

Let’s look at what the article told us:

1. ULF (Ultra Low Frequency; > 5 hour cycle length) ULF are variations that are happening at around 0.0033 Hz or about once every five hours. This frequency is associated with the circadian rhythm.

2. VLF (Very Low Frequency; > 25 seconds) This frequency is occurring at a power spectrum of 0.04 Hz and is related to and affected by temperature regulation and the humoral systems. If you’re cold, your heart rate slows down. If you’re hot, it speeds up. The interesting trait of this frequency is the connection to the immune system. Once again this is the reason that HRV is looked at so closely nowadays.

3. LF (Low Frequency; > 6 seconds) This frequency is directly linked with sympathetic and parasympathetic nervous activity. Basically, this frequency will tell you if your autonomic nervous system is working efficiently. The ANS’s ability to work efficiently is directly linked to your body’s ability to maintain homeostasis – or more directly put, a person’s ability to recover from exercise. Even more importantly, this is an indicator of the body’s ability to maintain life.

4. HF (High Frequency; 2.5 to 6 second cycle lengths) This frequency is synchronized with one’s respiratory rhythm, and it is primarily controlled by the cardiac parasympathetic innervation. That’s why there is a breathing guru on every block. It’s because of breathing’s ability to positively influence the parasympathetic nervous system. This is the system that keeps us calm, keeps our immune systems ready, and allows us to focus and make prime executive decisions. However, if the guru has no idea about the strong respiratory pattern of cardiac vagal motoneurons in the nucleus ambiguous, then consider finding a better guru.

Putting It Together

Let me summarize my findings, so you can make a decision on whether or not to use HRV. First, HRV is a great predictor for cardiovascular disease and early death. More variability indicates a strong ANS capable of maintaining homeostasis. Less variability is an indicator of the ANS’s inability to maintain balance in the body. However, regular participation in cardiovascular exercise and/or resistance exercise (I recommend both) over an extended period of time can decrease your resting heart rate by increasing the heart’s size, the contractile strength, and the length of time the heart fills with blood. The reduced heart rate results from an increase in activity of the parasympathetic nervous system – and perhaps from a decrease in activity of the sympathetic nervous system.

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HRV is also a great indicator of an athlete’s ability to recover from the stressors of training. The ANS and humoral systems are both ways that the body adapts both in the short term and long term from the stress of training. I believe that a bit more data is needed, and I believe this to be a bit more individual than some would lead us to believe. However, tracking the data and associating the data with performance over a long period of time could be invaluable. I am looking forward for HRV to be one of the many variables that we track at Lenoir-Rhyne University – along with velocity, CNS readiness, ECG, attitude markers, and hopefully muscle fiber makeup and neurotransmitter dominance. Standby!

Here are all the questions I answered after reading the research and digging myself out of the rabbit holes it kept sending me in:

1. Define heart rate variability, as is you were explaining the concept to a layperson.

Your heart doesn’t beat evenly. If your resting heart rate is 60 BPM, you won’t find that there is exactly one second between heartbeats. Your heart is directly linked to the autonomic nervous system with the sympathetic nervous system speeding the heart up and the parasympathetic slowing it down. HRV is also linked to circadian rhythms (sleep-wake cycles) and respiration. Therefore your heart is constantly reacting to stimuli in your environment based on the commands given by the ANS. The amount of variance is directly related to health. A larger heart rate variance indicates a healthy body able to react to negative stimuli and yet relax afterwards. A low variance is directly linked to cardiovascular disease. Stress, pain, and chronic inflammation and disease are all linked to lower HRV. Therefore, controlling stress, proper breathing, and focusing on overall good health are all ways to ensure a higher HRV.

2. Describe the relationship between heart rate variability and general health.

Since low heart rate variability is a reliable predictor of cardiovascular disease, I’d say HRV has a very solid relationship with general health. HRV seems to be a solid indicator for the body’s ability to fight off disease, especially where cardiac disease is a concern. Low HRV is a solid indicator of stress and pain as well.

3. Describe the relationship between heart rate variability and exercise.

HRV has become prevalent in several sports as a way to predict an athlete’s readiness and ability to recover. HRV, as we learned in the article, is also tied to the endocrine system, which is also regulated by the ANS. A low HRV shows athletes and their coaches the ability of the athlete to recover from exercise. If your ANS is tanked, the athlete doesn’t have the ability to respond to the stresses of exercise. Exercise at the end of the day is a stress stimulus that the body responds to with the ANS to recover and get stronger. If one has a low HRV, I would recommend diet and sleep improvements, low intensity exercise, and breathing meditation to slowly alter their HRV to a higher variability.

4. Can heart rate variability be modified by exercise training, and if so, how?

It appears that moderate low-intensity exercise can improve heart rate variability over time without causing lasting stress from the sessions themselves. It makes sense that if HRV is tied to such systems as the ANS and the respiratory system, then improving these systems through exercise could in turn improve heart rate variability over time.

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HRV is easier to monitor now than ever before. If it is at all possible, I firmly believe you should learn more about it – whether you are a coach or an athlete. Once again I want to thank my amazing professor, Dr. Alex Koch for developing the most impactful curriculum ever imagined at Lenoir-Rhyne University. If you want to major in exercise science, LRU is the best – especially for future strength coaches. If you want to become a weightlifter at LRU, email me at Travis.Mash@LR.edu. Thank you for reading and let me know any questions you might have.