I am particularly perplexed by Bikram’s next claim that higher temperatures improve the function of the nervous system, meaning that messages are carried more rapidly and efficiently to and from the brain or spinal cord (you think more clearly).
I know that when I am hot, I am usually bothered and my brain is certainly not thinking nor functioning more clearly. We also know that dehydration due to excessive sweating in a hot yoga class where you are either not allowed or discouraged from drinking water during class will causes symptoms ranging from fatigue, nausea, vomiting, FOGGY THINKING, and dizziness. Dehydration can also cause a sense of euphoria. A student once told me they did not feel and were told they were not allowed to leave the room and if they did leave the room they weren’t allowed back in. WTF!
If you don’t believe me, then believe a study conducted by Hideki Kinugasa and Kaname Hirayanagi titled Effects of Skin Surface Cooling and Heating on Automomic Nervous Activity and Baroreflex Sensitivity in Humans conducted at the Department of Hygiene, Nihon University School of Medicine, Itabashi-ku, Tokyo Japan, found a suppression of cardiac vagal nervous activity (the nerve that activates the parasympathetic nervous system) and an enhancement of cardiac sympathetic nervous activity (fight or flight response) can be caused by skin surface heating. The sympathetic nervous system activates when there is threat. It does not matter if the threat is perceived or real. The physiologic changes result in increased heart rate, blood pressure, respiration, skin conductance and changes in brain wave activity changes. Does this mean that messages are carried more rapidly or efficiently to and from the brain or spinal cord meaning you are thinking more clearly? Well, have you ever experienced an activation of your fight or flight response? It happens when you almost get into a car accident or you did accidently get into a car accident. Fact: The thinking part of our brain stops, slows down or is suppressed and the survival, action part of our brain, takes over. Our rational mind disengages and our only concern is focused on fear, not remembering facts. We are not concerned with making clear concise well thought out decisions nor are we thinking about the consequences of those decisions. We are only hyper-focused on our short-term survival in the moment.
I want to take a moment to address skin conductance because maybe Bikram is referring to this phenomena. The skin conductance response is also known as the electrodermal response or galvanic skin response. It is the phenomenon that the skin momentarily becomes a better conductor of electricity when either external or internal stimuli occur that are physiologically arousing. Heat will increase skin conductance by releasing moisture, aka, sweat. Water is a better conductor of electricity and thus, increases skin conductance. This also, as stated before, elicits the stress response system of our central nervous system. There is no evidence stating that increasing skin conductance improves mental clarity.
Another study by Alicia Ramsey et al., in their study Activation of the Human Sympathetic Nervous System: Effects on Memory Performance, concluded “The fight-or-flight response activates the sympathetic portion of the autonomic nervous system resulting in numerous physiological and mental alterations. At a biological level, activation of the “fight or flight” response subsequently stimulates two endocrine systems: the hypothalamic-anterior pituitary-adrenomedullary axis (HPA) and the sympatho-adrenomedullary axis (SAM). Activation of HPA axis releases the stress hormone cortisol, a glucocorticoid, from the adrenal cortex, while activation of the SAM axis causes release of adrenaline from the adrenal medulla. The physiological effects of these hormones on the body are widespread and may include impaired cognitive function.”
Let’s assume that no one’s fight or flight response system is being activated by a hot yoga class. Well, remember, we sweat to cool the body down and maintain our normal healthy body temperature at 98.6 °F. Bikram claims these benefits are from the body temperature increasing during class, but our body temperature does not rise BECASUSE we sweat. For arguments sake, let’s say our body temperature does elevate (without dehydration). How high is Bikram claiming our body temperature is rising? There is increasing evidence that elevated body temperatures whether infective or non-infective leaves our central nervous system particularly vulnerable to damage from hyperthermia. Hyperthermia is defined as an abnormally high body temperature caused by a failure of the heat-regulating mechanisms of the body to deal with the heat coming from the environment. Normal body temperature is considered to be 37°C (98.6 °F) with hyperthermia defined as a body temperature above 37.5°C (99.5°C) and severe hyperthermia is > 40°C (104°F). The neurological and cognitive consequences of hyperthermia by Edward James Walter and Mike Carraretto “briefly review the cognitive and neurological effects of hyperthermia on the brain, and examine some of the proposed mechanisms by which cerebral damage is caused.” They go on saying “A single episode of hyperthermia may cause short-term neurological and cognitive dysfunction, which may be prolonged or become permanent. Considering a healthy hydrated human body as a thermo-regulating system in place, it highly unlikely hyperthermia sets in during a Bikram/Hot yoga class.
Please remember, Bikram Yoga/Hot Yoga classes are not sauna conditions. Sauna is extremely good for you. I will, one day, discuss the benefits of the sauna. Until then Dr. Mercola has many beautiful articles outlining the benefits of sauna.
Let’s create a conversation!
Please ask questions or comment!