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We all know that yogasana as exercise is good for our body and our mind, but why is this so? How can we rationalize this within the context of the physiology of muscles? And what can we understand anew by taking this technological approach to something that up to now has been so free of such scientific thinking? I believe that the answers to questions such as these are more or less revealed in a very recent paper entitled “Hormesis and Exercise: How the Cell Copes with Oxidative Stress,” authored by L. L. Ji, Z. Radak, and S. Goto, and published in the American Journal of Pharmacology and Toxicology, volume 3, 2008, on pages 44-58. A free copy of the full text of this article is available on the Internet.

 
Not only is this work on hormesis directly applicable to the practice of yogasana, though this is never mentioned explicitly by name, still the connections are obvious I think. Moreover, it is based upon a phenomenon which is currently the center of a vigorous debate in the scientific literature, which pits old but accepted pharmacological ideas against a set of newer ones, which offer great promise for changing the directions of medical research, if they are in fact true.

Hormesis

 
The phenomenon at the center of the debate is the phenomenon called “hormesis” (Greek for “to excite”) as it applies to the question of the dose-response curve for drugs. The standard expectation in this regard, Figure 1.A, is that as the dose of some chemical injected into the body increases, the body’s response to this also will increase until the dose is so large that the injected material becomes lethal. Of course, it follows naturally, that at zero dose (”0″), the response is zero.
 

Figure 1.A. The idealized dose/response curve for the injection of a drug into a living system, with the measured responses shown for drug doses of 1 to 10 in arbitrary units. In normal practice, the unexplored region between zero dose and the lowest dose used in the experiment (*) is simply a straight-line interpolation, as shown by the dashed line. At zero dose, there is often some nonzero response due to existing environmental factors, for example, and at dose levels of 10 or higher, the lethal limit has been reached and exceeded. In fact, many careful experiments show that in the very low-dose region, the experimental curve is more like that shown by the dotted line in the figure, due to hormesis.

Figure1.B. The interpolated dashed curve at low dosage and the true curve showing the hormetic effect (dotted curve) in a plot of relative risk for breast cancer versus number of alcoholic drinks consumed per day.

 

Figure 1.C. The interpolated dashed curve at low dosage and the true curve showing the hormetic effect (dotted curve) in a plot of the relative risk of tumor formation versus the dosage of ionizing radiation in rads.

The argument centers around the behavior of the curve between the origin at zero dose “0″ and the first measured point, labeled “*” in the Figure. It is natural to assume that the curve in this region simply rises in concert with that determined experimentally at points beyond “*” as shown by the dashed line in this region of the dose-response curve. Experimentally, thanks to careful work in literally hundreds of dose-response systems (drugs, poisons, radiation, muscle contraction, respiration, heart attack, etc.), the curve is now recognized to have a rather different shape, that of the dotted curve in Figure 1.A. This is in accord with the statement of the toxicologist Paracelsus in the 1400’s, who said, “All things are poison and nothing is without poison, only the dose makes something not a poison.” In more modern terms, hormesis says that all things are fatal to us if we take them in such large quantities that they generate unbearable stress in the body, however, at much smaller doses, the stress is not only bearable but capable of curing, and therefore is beneficial! Note that with the hormesis effect in action, the response can even be below that of “zero dose” showing that some other, possibly environmental effect, must be active other than the purposeful exposure to a “noxious” substance.

 
As further examples of the hormesis effect, consider that one is statistically more likely to survive a major heart attack if one has already had several smaller attacks, and that respiratory efficiency is greatly enhanced if one practices breathing air contaminated with a small amount of carbon monoxide, a deadly poisonous gas! Regarding bacteria and their negative effects, consider that communities with non-zero concentrations of bacterial contamination in their drinking water survive better when the concentration rises to dangerous levels, than do super-clean communities which normally have zero contamination and then experience a sudden rise to the same dangerous levels. The argument then centers about the question, “How can something that is a violent poison, corrosive, infectious, deadly, etc. ever function in a beneficial way, even at low concentrations?”

Mitochondria, ATP, and Muscle Contraction

 
In response to the question posed above, let’s first consider the situation in regard to how hormesis may play a role in yogasana practice. Energy is obviously required to contract a muscle, any muscle, be it skeletal, cardiac or smooth. The energy driving this contraction involves the ubiquitous molecule adenosine triphosphate (ATP) that is present in the resting body in quantities large enough to drive most muscle contractions for a few tens of seconds. Once exhausted, the body then turns to nuclei within the muscle cells called mitochondria, which can produce more ATP as long as they receive glucose and oxygen from the blood stream. A contracted muscle can consume up to 100 times as much oxygen as the same muscle in the resting state. The chemistry involved in this step is complex (see the above mentioned article) and seems to change with age, for as we age, the byproducts of this mitochondrial process yielding ATP also produce increasing levels of products known as Reactive Oxygen and Nitrogen Species (RONS). Rephrased in terms that more readers may be familiar with, the RONS are strongly oxidative chemicals, and only another class of chemicals called anti-oxidants can withstand their actions. Paradoxically, RONS in some situations are helpful, acting as mediators of signal transmission and other biological processes.

 
As the RONS are highly reactive and are almost totally nonselective, they work to tear apart the mitochondria and other nearby structures (resulting in cell aging) until the damage exceeds a certain limit (resulting in cell death). This production of RONS is held to be one of the major factors in regard to good health and longevity, with excess RONS leading to poor health and a shortened lifespan. Given that the production of RONS is greatly increased by increased contraction of any muscle, it would appear that the secret to a long and healthy life is to avoid all exercise, including yogasana practice!

Homeostasis/Balance

 
In a healthy body, there are a multitude of sensors that measure various properties of body function and then subconsciously make adjustments to the system so as to maintain these functions within certain specific limits for good health. I speak of the sensor systems that maintain the core of the body temperature at 98.6 degrees F regardless of the external temperature, for example, or those that maintain blood pressure within narrow limits, control the levels of oxygen and carbon dioxide within the blood, close the iris of the eye in strong light, etc. This subconscious process of restricting body variables within healthy limits is known as “homeostasis,” and is indispensable for life.

 
Fortunately for all of us, there exists in each of us a homeostatic balance mechanism with regard to the oxidation/anti-oxidation forces battling it out within every muscle and organ in the body, 24 hours a day, every day.

Stress and the Hormesis Mechanism

 
When a variable function of the body approaches a preset limit in the body due to some externally applied stress such as exposure to too low a temperature, then the sensor activates a homeostatic action that works to counterbalance the errant stress impressed externally. In this case, it would be the onset of shivering which warms the body through the generation of body heat by muscle contraction. The benefit of this homeostasis is not only that it can work to resist a body function from assuming extreme values, but it also exercises the resisting mechanism. By exercising any homeostatic balancing mechanism, it becomes possible to reset the limit higher if there is a reason to do so, and it gives one a better chance of successfully turning back a truly large and instantaneous stress because the balancing mechanism has been exercised in the past and so is immediately ready to respond.

 
In a way, the hormesis phenomenon can be rephrased in terms of vaccination. By vaccination, one introduces a small but specific external stress on the immune system, and this then primes the body to be able to battle the real threat if one ever meets it again. Without the vaccination, the real threat is such a large and acute stress on the system that we yield to its effects, but with the strength gained by meeting it a few times in a weakened condition through vaccination, one is able to defeat it.

 
Along lines that are more physiological than immunological, ionizing gamma radiation of 600 Rads or higher intensity results in the rapid appearance of radiation-induced tumors, however when exposed a few times to a hormetic dose of only 20 Rads or so, the body is “vaccinated” against radiation, and the rate of tumor formation is then lower than it is when the radiation dose is zero! Similarly, though the consumption of more than one-half of an alcoholic drink per day is harmful in regard to breast cancer, and increases with larger daily amounts of alcohol, at only one-quarter of a drink per day, the resistance to breast cancer is even less than if no alcohol is consumed at all, Figure 1.B.

Redox Balance/Priming

Applying the above reasoning to exercise, if the exercise is muscular but moderate in intensity, then the oxidative stress incurred by the body will be met and conquered successfully by homeostatis because the body has met this stress before and so does not fade when the stress appears. In this case, it is imperative that the homeostatic control be exercised often and at low intensity. If, instead, the stress appears instantly and is of very high magnitude, then the homeostatic mechanism will not be able to handle it, and one must suffer whatever the consequences might be. In this way, by moderate exercise, one vaccinates the body against the stress of RON’s production and the consequent oxidative damage initiated by muscle contraction.

 
But wait, you say! In yogasana practice we are involved with muscle stretching rather than contraction! Not true! In stretching a muscle, we are always anchoring one end of a muscle by contracting antagonist muscles, while we pull the other end away from the anchoring point, often by contracting yet other muscles. And even when in savasana, the heart and the respiratory systems continue to work and to produce their burdens of RONS.

 
Exercise that involves muscle contraction is beneficial provided that it is done at a moderate level and is done regularly/daily. Were your exercise plan based on walking/running for example, do walk/run every day, but only slowly allow the level of exercise-induced oxidative stress to rise. Were you at this initial point in your running life and decided to run a marathon, you might seriously injure yourself, for the redox balancing mechanism has not been adjusted for the large stress inherent is such an undertaking.

 
Q: How then do you ever reach the marathon level? A: You do so by incrementally increasing the stress of your activity, thereby giving the homeostatic mechanism a chance to strengthen as the oxidative stress increases. Done slowly over time, you will be able eventually to recover from the stress of a marathon-insult to the body with no lasting ill effects.

 
In a study relevant to yogasana students on the effects of diaphragmatic breathing on oxidative stress, it was shown that following a full day of exhaustive exercise, one-hour of such yogic breathing was far better at reducing the marker for cortisol (a strong indicator of oxidative stress) while increasing that for melatonin (a strong antioxidant), as compared to simply sitting and resting.

The Application of Hormesis to Yogasana Practice

Applied to yogasana practice, the lesson is clear, and totally in line with yoga as taught by BKS Iyengar. Start with a practice of only moderate intensity, but do it regularly. The term “moderate exercise” for the beginner implies that the work does not make the exerciser feel distressed or uncomfortable. As you do this, your strength will increase and so too will your resistance to oxidative damage, otherwise given no other health problems. Continue doing this as long as you wish to remain healthy. If your age and health allow it, you should incrementally increase the intensity of your practice while you maintain its regularity.

 
This plan is not only a good one for the long term, but is just as applicable for the moment, say in regard to incrementally approaching inverted postures such as Sirsasana. In this case, the problem may be a precipitous increase in the intraocular pressure if one goes immediately into full inversion, however, this can be avoided by incrementally inverting over a matter of weeks instead of inverting fully within a few seconds. Moreover, the hormetic mechanism is said to be applicable no matter whether the stress is physical, mental, pathological or environmental, irrespective of whether the stress is oxidative or not. Thanks to hormesis, whatever does not kill you can make you stronger!

• Adapted from a longer article on this subject submitted to Yoga Rahasya, 2010.

Mel Robin can be contacted at: Email Mel

Tags: antioxidation, BKS Iyengar, exercise, homeostasis, hormesis, Mel Robin, oxidative stress, redox balance, RONS, stress, yoga

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