HRV (heart rate variability) is a special way of measuring heart frequency. The term “variability” means changes of interval or distance between two heartbeats.
Intervals between two heartbeats are measured in milliseconds. HRV is a result of a lot of different biological rhythms which exist in our bodies. So, based on its rhythm, we cannot compare a heart to a clock that ticks every second equally, but the distance between two heartbeats is always different.
That is important to know because the variations in the duration of certain intervals between beats are important for physical, mental, but also emotional function of the organism. We must not equate the terms “heart rate” (HR) and HRV.
Why is HRV important and where is its place in the context of training?
The muscles are the only important thing that our progress depends on in power training? No, there is one more, equally important (for some forms of training primary) system on which it depends if the line (curve) of progress will be going up, stand still or go down. That is the nervous system that also adapts to stress to which it is exposed and in that adaptations it becomes more capable and efficient.
First a few words about the nervous system…
The nervous system is composed of two parts:
- Voluntary – it enables movements, like muscle activation
- Autonomous – it controls body functions that are important for surviving (breathing, digestion, heart, blood pressure,…)
We will forget for a moment about the voluntary part of the nervous system and focus on the autonomous.
That part is composed of two braches – sympathetic and parasympathetic – which have opposite effects. Sympathetic part enables a quick reaction when the body is exposed to some kind of stress (known as “fight or flight” reaktion).
Parasympathetic part is opposes sympathetic part by its effect and it creates an atmosphere for rest and recovery in the body.
How does the effect of sympathetic and parasympathetic part reflect in the heart in the state of stillness?
Heart rate varies and it is dependent on breathing. With every exhale, the brain sends a parasympathetic signal that slows down the heart. When we inhale, parasympathetic signal is weakened, and sympathetic comes to the fore which leads to a light acceleration of the heart rate.
The ideal situation is the one where an athlete has a strong sympathetic reaction to acute stress (training), and equally strong and dominant parasympathetic reaction when the time comes for rest and recovery. Comparing to the average athletes and recreationists, top professional athletes have significantly stronger sympathetic, and parasympathetic reaction in corresponding phases.
So, now we have a connection between HRV, which fairly represents (non)balance of the sympathetic and parasympathetic part and the roles of these two components of the nervous system in training (efficiancy of the training itself, as in the speed and quality of the recovery).
For the athletes it is very important because by measuring HRV, it can be estimated if the body needs more recovery or is it completely ready for a new stressful stimulus. The practical importance of HRV is of great importance and out of the sport context. Low HRV predicts higher probability for death to occur because of other causes, especially sudden death.
Generally, high HRV is connected to better health and people which are more fit than the ones with low HRV.
Fortunately, there are ways to “train” HRV and in that way achieve the wanted high HRV. One of the techniques is HRV biofeedback, which was first used in Russie with asthma patients. Later this method in USA found its wider use in the states like chronic fatigue, chronic obstructive pulmonary disease, various cardiovascular disorders, chronic pain, psychiatric states like anxiety and anger, etc.
Every person has specific “resonant frequency” where the variability is the highest.
There are more and more ways that can measure HRV. From the expensive ones, designed for specialized institutes and institutions, to the simple ones for everyday personal use. Some of the mobile applications that serve that purpose are eg. Ithlete i BioForce.
By measuring HRV and respecting the read off results in everyday approach to the training and recovery we can anticipate overtraining. So, Go-Hard-Or-Go-Home catchword, however motivating and pushing it sounds, when we take into account all that has been said, it’s not that worthy always.
So, when we got the information about HRV, on the basis of its values we can objectively respond to the question if the body is recovered enough for the next training or we need to give it more time to do it. HRV method is an effective way to avoid overtraining.
If we would get our bodies into the state of overtraining (of which can be discussed and debated for a long time), we would have a situation where the sympathetic system is in a completely burnt state and parasympathetic system would become dominant. Symptomatology of overtraining fits into a so called general adaptation syndrome (GAS).
This syndrome is actually a stress reaction of the body, and it has 3 phases (stages):
1. Functional overtraining
Most common is that the first phase is not followed by obvious symptoms so it is easy to predict and ignore. However, even here HRV is measurable, so its importance is obvious in the early diagnosis of overtraining.
In the first phase a person can feel fatigue, disturbed sleep, increased feeling of hunger, increased desire for certain foods that are not consumated usually can occur etc.
Adrenal dysfunction can be the reason for these symptoms because the level of cortisol increases. The right reaction of an athlete in this phase of GAS is adaptation in the training approach, diet, stressful circumstances and other. If this introductory phase of GAS is not noticed or if its subtle signs are ignored, the symtoms will get intensified and the body will go into the second phase.
2. Sympathetic overtraining
In the most cases, overtraining is not diagnosed until this phase.
Overtraining
Heart rate in the state of stillness is significantly increased, as is the rate during the training. This second phase of overtraining is expressed more in athletes for who anaerobic way of training includes most of the whole training. This especially goes for athletes that practice a very high volume of training.
Adrenal dysfunction gets even worse during this phase so the level of cortisol can be increased to abnormal values. This has as a consequence collapsing of various balances in the body, and increases fat storing which is closely related to low tolerance to carbohydrates that occurs with it. Furthermore, high level of cortisol lowers the levels of testosterone and DHEA, important for muscle recovery speed.
The good news is that the disbalance of the hormones can be pretty easily corrected with some interventions in food and training. If, however, it is not done, the athlete goes into phase 3.
3. Parasympathetic overtraining
In the final phase of overtraining, which occurs when the symptoms of phase 1 and 2 are completely ignored, the organism is completely exhausted. A lot of hormones are at their minimun so for example, unlike in phase 1 and 2, the cortisol here is very low.
A number of psychophysical symptoms are present, like lack of motivation to compete and train, and common injuries. Because of the parasympathetic domination, the heart rate in the state of stillness is low. The level of aldosterone is low, which leads to increased loss of sodium. Recovery and getting the organism back to the optimal state is a very hard and demanding task.
I hope that after this text, the importance of HRV is very clear, and its role in traversing the state of overtraining. HRV is a relatively new term, but I am sure that of this valuable method a lot more will be spoken in the future.