Sports Science to Improve Performance

November 25 2016

Dr. Matt Mortenson

Dr Matt Explains How HRV (Heart Rate Variability) Can Be Used to Optimize Training: Train, Rest & Recover to Perform

by Dr. Matt Mortenson
posted Nov 25 2016

Imagine if there were a way for you, as an athlete, to ascertain the effects of your training interventions in real-time so you could maximize training without compromising performance. Perhaps something like an RPM gauge that tells us whether a certain aspect of training is effective or just a waste of time. There would be no more guessing which workouts were effective. Athletes could determine when to rest and when to train hard - dramatically reducing the chances of overtraining and consequent poor performance.

Having some type of feedback each day to guide us through the rigors of training is certainly appealing, and holds value. By combining heart rate variability (HRV) and technology we can do just that. Over the last decade, the scientific community has produced numerous studies that support the value of using HRV as a training intensity guide. HRV also correlates with predicting fitness levels, so it can be used to track changes in physical fitness. The best heart rate monitors and apps measuring HRV can also serve as a potent health risk assessment tool to aid in optimizing training and improving general health.

What is HRV? HRV is the variance found between successive heart beats in time. In other words, it is the difference in time measurement between heart beats. Our heart does not beat in perfect rhythm but varies depending on the stimuli acting upon it. Temperature, emotions, stress, sounds, time of day, hormones, etc. all effect HRV. For example, when we breath in or hold our breath, heart rate increases. The reverse is also true, when we exhale heart rate decreases. This phenomenon is called respiratory sinus arrhythmia and occurs every second of every day with every breath we take. In short respiratory sinus arrhythmia reflects how our respirations influence our heart. How can we exploit this knowledge in practice? I had the opportunity to observe some of our national men’s players prepare for the World Cup in England. The players were put through a series of shuttle runs. By the end of a few shuttle runs, some players were close to their maximum heart and respiratory rates, doubling over and gasping for air. One of our strength & conditioning coaches kept repeating to players the need to “control breathing to control heart rate”. What this coach was trying to teach the players was a biofeedback technique, using respiration to slow down and control their heart rates. With practice, this technique would lead to quicker recovery times and the ability to repeat intense efforts more frequently.

Just how sensitive is HRV? HRV is not only reliable and reproducible, it can also provide a quantitative analysis of the Autonomic Nervous System (ANS). One of the first uses of HRV as a prognostic medical tool goes back to a 1978 study conducted by Wolf et al., in which they found that analysis of HRV variance from an ECG could predict hospital mortality. HRV can also be used in medicine as an excellent predictor of death and non-fatal arrhythmic events after myocardial infarction and can identify the presence of diabetic neuropathies. It is sensitive enough that physicians can use it to determine the effectiveness of pharmacological drugs like beta-blockers. It can also play a role in detecting food allergies. Researchers have also found that using HRV monitoring helps detect the early onset of a condition called Pregnancy Induced Hypertension (PIH), allowing life saving interventions to prevent the escalation of the condition and save lives. More recently Cooper et al. found that heart rate variability predicts the level of inflammatory markers and the vagal (parasympathetic) component plays a role in the anti-inflammatory pathway. This finding has the potential to revolutionize our understanding of how our bodies recover from stress. We can potentially use it to gauge the rate of recovery.

Even more recently HRV was studied among rugby players. Researcher took the Brazil national team (tryouts), just prior to the Olympic games and studied the validity and reliability of short term HRV monitoring. The results of the study were quite remarkable and help to support the use of HRV monitoring in a practical field setting. It is therefore reasonable for club players to apply the same methods in their training so they may reap the benefits.

In medicine, the primary aim of monitoring HRV with a heart rate monitor is to determine if the medical interventions offered to a patient result in an improvement in HRV or cause the heartbeat to remain rigid. In the sporting world, it is used to help optimize training as it can quantify the stress and fatigue levels in the nervous system; therefore, allowing us to navigate daily training intensities and work loads to avoid overtraining syndromes, make better use of time, and stay healthy.

The connection between heart rate (HR) and HRV is that a high heart rate generally correlates with low HRV and vice versa. High HRV correlates with good fitness, low stress and well-being while low HRV correlates with poor fitness, lack of well-being, illness, overtraining state, etc. The practical application is as simple as taking your heart rate but, instead of using HR, we measure HRV.

The connection between HRV and the autonomic nervous system (ANS) is quite powerful. HRV reflects the efficiency and balance with which the two branches of the ANS function. The variation in our heart rate is primarily caused by the effect of the parasympathetic nervous system’s activity on cardiac function. When autonomic function breaks down, the parasympathetic nervous system is the first to take the fall. This results in a rigid heartbeat, which is reflected as low HRV. Low HRV correlates with poor adaptability and poor functional capacity.

The autonomic nervous system (ANS) is responsible for regulation of most the internal body functions such as heartbeat, breathing, digestion, gland secretion, etc. Proper regulatory activity of ANS provides an environment in which the body can adapt to stress. Training is considered stress and athletes constantly place their bodies under stress by undergoing exercise which lead to physiologic changes. These changes are carried out by our nervous system along with neurohormonal, thermoregulatory, immune and localized muscular responses. Physiological change, or adaptation, is an important principle in exercise physiology. The philosophy of train, rest and recover is not new. Training exposes the athletes body to a process of stress and adaptation. Adaptation is the process of changing the body’s internal state and function in response to external factors. When adapting to a changing environment our bodies ultimately seek a state of homeostasis. A state of homeostasis is achieved when equilibrium and stability is maintained in the body’s functions. It is important that we use adequate amounts of energy and resources to function and survive. Without a balance, we are at risk for illness, disease, or compromised athletic performance.

Consider it like a tug of war. Training activates the sympathetic nervous system while rest activates the parasympathetic system. Withdrawal from exercise reduces sympathetic involvement and increases parasympathetic involvement and the contrary is true. At rest our parasympathetic system is more active than the sympathetic. Neither division of the ANS is ever completely absent. Both branches are always active as our lives depend on it, its just a matter of degree. A good example of this phenomena can be witnessed by observing a cat and mouse chase. Since our audience is rugby players perhaps it is a bone crushing prop chasing down a weary winger. When the chase is on, our brains turn on the flight or flight response… out of survival. Blood is directed from the organs to the muscles, heart rate and respiration increase, the adrenal glands pump out adrenaline and various other neuro-hormones and we consume energy as fast as an airplane burns fuel. After the chase, respiratory and heart rate return in line, the adrenals glands relax, blood flow to muscles decreases and energy expenditure is reduced. So any changes in the surrounding environment, like training, may cause our body’s functions to deviate from their baseline homeostatic levels and require increased energy expenditure. The adaptation mechanisms work hard to bring those functions back to balance. The brain and autonomic nervous system (ANS) are primarily responsible for this process. Healthy individuals are quite capable of maintaining homeostasis due to their high adaptation reserves. Chronic influence of stressors (such as overtraining) tends to exhaust the body’s adaptive capabilities and make it vulnerable to developing illness, disease and/or poor performance.

The main goal of training is to improve our potential during competition. When we overtrain we weaken the nervous system and this weakens our ability to control function, which can result in poor performance. We can monitor the strength and weakness or adaptability of our nervous system by studying HRV. Even early indicators of weakness, poor adaptability or overtraining can be observed by analysis of HRV.

There are several software developers that have created apps so we can monitor HRV via our phones. Most companies only require you to use a heart rate monitor strap that measures R-R intervals. These are usually the Bluetooth HR and ANT + compatible HR monitor straps. You download the app, put on your HR monitor strap and pair with app. Once paired, you can take a measurement. Ideally, a measurement should be taken each morning before drinking or eating. I recommend taking a measurement as soon as you wake up, either laying supine or in a seated position. It only takes a few minutes. It is very important to keep your morning reading environment consistent. Whether you take the reading laying down, sitting or standing, it is important to be consistent. There should be no noise or external interference. Try not to talk or move, just relax and breath. If you can keep the measurement environment consistent, you will find the measurements are more reliable and accurate. Further, you will need to acquire several weeks of data. This has become a common practice among sport scientists and coaches until a base trendline is established. Once you have an established base trendline, one can then adjust training loads and intensity based on daily readings. For example, let’s say Monday is scheduled for High Intensity Interval Training (HIIT) in the morning and Olympic lifts in the late afternoon. Tuesday is pitch training and Wednesday is track/sprint training. These are all very intense workouts. On Monday morning, you notice a dramatic drop in HRV and resting pulse along with a drop in the mean (average weekly) reading. It may be prudent to re-evaluate your training over the next few days. Perhaps either by lowering the intensity of the workouts, or by resting completely. The reverse is also true. Perhaps Sunday and Mondays were scheduled for rest but your HRV reaches a new high. This would be an excellent time to train hard instead of resting. HRV monitoring increases our awareness regarding how our bodies are responding to training and stress and can help guide behavioural changes, which may then improve overall performance.

One question we should ask coaches is how they know a specific training program is working for each and everyone of their players. Rugby coaches are very guilty of running fitness drills for their entire team together. They forget that players are individuals and do not share the same physiologic attributes. It does not make sense to have a 250lbs prop run the same distance or sprint as fast as a back. Just like it does not make sense to have a winger squat the same amount as a prop. Some of the basic principles in training are individualism, sport specificity and overload. Having the entire team do the same thing in training breaks most of these training principles. We need to monitor each player individually and adjust training according to how well they do or do not absorb training.

To quickly summarize

- HRV measures the physiologic response of the nervous system. The nervous system controls every bodily function and is the most important system to monitor in athletes;
- HRV testing is reliable and valid if the individual follows correct methods of measurement;
- HRV has been studied in rugby players and has found to be both valid and reliable in a practical setting;
- Monitoring is quick and easy and should be done daily until you establish a base trendline;
- HRV monitoring increases awareness of health (i.e. nervous system) status, so daily adjustments can be applied to a training program to maximize benefits;
- HRV monitoring improves behavioural changes so athletes can improve health and consequently fitness and performance; and
- We must recognise that there is a cost of performing/training and we only have so much energy per day to undergo training. The idea is to dial in to how much energy a specific individual has per day and match that with training load and intensity so the individual athlete can maximize training and performance without over-reaching or over training.

Happy training!

Dr Matt Mortenson DC, CSCS, SFR

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