Autonomic nervous system (ANS) and training

Autonomic nervous system (ANS) and training

The ANS is an relatively important component of our nervous systems and very important for all aspects of performance.
First of all it branches out to almost all organ systems in our body, controlling many important vital physiological functions too important to be controlled by our conscious control. Our heart beats even if we don’t realize it and we cannot control it.
Secondly, it is a beautifully designed control system with two major braches, the sympathetic (SNS) and the vagal or parasympathetic system (PNS).
Thirdly it is a very fast, electrical system, running through nerves at high velocity. This is necessary, since it greatly contributes to our survival as a species, responding very quickly to changes of (perceived) threats from the environment. It is an important part of our ancient survival systems and allostatic systems that maintain our homeostasis.

The ANS is responsible for adaptation to exercise (immediate) and our adaptation to training (epigenetics).
The functioning of the sympathetic part of the ANS can be compared to the “accelerator” of a car, geared towards spending energy for survival (fight-flight or perform)  whereas the vagal part can be compared to the “brake”, geared towards saving, conserving or recovering energy. It’s the recovery part of our ANS.  Of course this is only a limited and simplified view of this complex system.

To show the short term  changes in the ANS, this example.
Just sit down, take your heart rate and stand up and take your pulse again, and you will find a fast change in heart rate, caused by a change in the ANS. The moment you start exercising (spending energy) your SNS starts to fire, and dominates over the effect of the PNS and your heart rate will speed up.The moment you quit the exercise the PNS will kick back in, dominating over the SNS, and your heart rate will slow down again.

Like any other physiological system, also the ANS is subject to the effects of training. Dependent on the baseline status, and the type of training, the ANS might change to SNS or PNS dominance. This is a functional adaptation to training, however too strong a dominance on either side, can be one of the signs of overtraining. This was already described by Israel, GDR,  in 1986, describing the difference in sympathetic and parasympathetic overtraining.(1)
The measurement of the status of the ANS is one of the many factors we can measure to monitor the status of the athlete and the training process. Be aware however that it’s not the only, nor the most important factor!

ANS testing
There are many different tests to measure the status of the ANS. In one of my earlier posts I mentioned the recent popularity of the HRV test. It’s fast, easy, kind of sexy  and can be described by software in impressive looking graphs. But don’t be fooled by its looks. Interpretation of the ANS is not as easy as one wants you to believe!
It can only show you the cardiac autonomic system, since the ANS does not operate as an all-or-none system, that fires as a whole. Dependent on the stimulus it certainly differentiates in the organs and tissues that it innervates. This can very clearly be shown by making psycho-physiological stress profiles as I have been doing for more than 25 years.
We connect a person to electrodes to measure ANS-controlled organs and tissues simultaneously:
•    Cardiac system: heart rate and HRV
•    Respiratory system: breathing frequency and amplitude
•    Skin: skin conductance/resistance or sweat secretion
•    Peripheral circulation: the capillaries at the toes or fingers by measuring the skin temperature.
•    Muscle tension: by EMG or electromyography.
•    One could also look at blood pressure or pupil size.

These functions are all controlled by the ANS, Think about what happens when you encounter a threat, the SNS is activated, and adrenalin (epinephrine) increases.
The heart rate is going up, the HRV is decreased, the breathing becomes higher (thoracic), but also you start to sweat, skin conductance is increased and the skin temperature decreases (you turn pale) and the muscle tone increases like e.g. at the m.frontalis or the m.trapezius.

Now you will say that in this way the ANS does fire to all systems simultaneously, but when you look at these stress responses to standardized stressors, you will see that these profiles change from one individual to another. In some people you find a large increase in heart rate, while the sweat secretion is low, whereas in others you will find a large drop in temperature. So this shows that the ANS works in a differentiated way, not as one system. Or as Morrison  wrote in the chapter “Organ Specificity  of Autonomic Nervous System Responses”: “… an organizational model featuring an extensive array of functionally specific output channels, which can be simultaneously activated or inhibited in combinations that result in the patterns of autonomic activity that support behaviour,  mediate homeostatic reflexes, and cope with injury and disease.” (2)

But there are many more  tests to measure the ANS, as a matter of fact more than 100 different tests.(3)  Especially in Germany in the 1920’s and 30’s the ANS was an important object for clinical studies.  Like the regulation of the cardiovascular system with the transition from lying down to standing up.(4).In later years Ewing used ANS tests to measure the effects of diabetes on the ANS as the case of diabetic neuropathy.(5)

We should not forget that doctors in Traditional Chinese Medicine, already used the pulse testing 2000 ago, in an attempt to measure the status of the ANS, even if they did not know the mechanisms, to diagnose and prognosticate the health status of the patients.

In sports, the HRV measurements were used already in the 1960’s by Soviet sports physiologists.(6)

From an early stage in my work as a coach I knew that the autonomic system would play a role in training. Recently I saw an old presentation of mine presented at the International Track and Field Coaches Congress in Barcelona in December 1988 (6).
I wrote: talking about the “speed barrier” in sprints and the levelling off of performance:  “The mechanisms which are known to cause this specific curve of adaptation are: the adaptation systems of the body, the hormonal system and the autonomic nervous system. The support of future research of the adaptation  processes and the unlocking of the secrets of the nervous system for performance improvement in track and field may be a way to prevent the use of drugs in our sports.” (in this last part I was wrong). Furthermore; “The role of a coach is to optimize the adaptation in the widest meaning of the word.” Meaning:  the adaptation of cellular, biochemical, physiological, anatomical, biomechanical, and mental processes.

I also stated: “The central nervous system is the dominant “performance-organ” of the sprinter. As soon as our knowledge of the central nervous system increases, much more information may be gained about the functioning, changing and optimizing of (sprint-)performance limiting aspects.” It took twelve years more to get my hands on the Omegawave system in order to be able do this.

1.    Israel, S: Zur Problematik des Übertrainings aus internistischer und leistungsphysiologischer Sicht. Med. und Sport, Vol.26, No.1, 1976, pg.1-12.

2.    Bolsi, C.; Licinio, J; Govoni, S. (Eds.): Handbook of the Autonomic Nervous System in Health and Disease;  Marcel Dekker, 2003.

3.    Frowein, R; Harre, G: Vegetativ-Endokrine Diagnostik; Urban & Schwarzenberg, München, BRD, 1957.

4.    Schellong, F: Regulationsprüfung des Kreislaufs; Theodor Steinkopff, Dresden, Germany, 1938.
5.    Ewing, D.J; Martyn, C.N; Young, R.J; Clarke, B.F: The Value of Cardiovascular Autonomic Function Tests: 10 Years Experience in Diabetes; Diabetes Care, Vol.8, No.5, 1985, pg. 491-498.

6.    Sarsanija, S.K: Trainiertheit der Sportler und Variabilität des Herzrhythmus; Materialien der 9. All-Unionskonferenz uber Morphol.Phsyiol.Biochemie der Muskeltätigkeit; Moskau, 1966, pg. 22-23.

7.    Kraaijenhof, H: Trends in Biochemistry and Biomechanics of Sprints Methodology;  Track and Field Quarterly Review, Vol.90, No.1, 1990, pg.6-9.

For further reading about the ANS.

Wilson-Pauwels, L; Stewart P.A; Akesson, E.J; Autonomic Nerves; B.C.Decker, Hamilton, Canada, 1997.

Jänig, W: The Integrative Action of the Autonomic Nervous System. Neurobiology of Homeostasis; Cambridge University Press, Cambridge, 2006.

Robertson, D.(Ed.): Primer on the Autonomic Nervous System. Elsevier, Amsterdam 2012.