This text was written for the French association Fédération Inter-enseignements de Hatha-Yoga (FIDHY) and will be published in “FIDHY Infos N°94 Juillet-Août 2023“.

Physiological mechanisms involved in tummo practices

Anne Laurençon-Loviton with the collaboration of Maxime Gamart

The practice of tummo is also called the yoga of inner fire, as it is associated with bodily sensations of inner warmth. Improving resistance to the cold is both a criterion for the successful implementation of Tibetan practices, and also a secondary effect of no importance to the practitioner: these practices are above all spiritual practices. Visualisations, body movements and breathing enable the practitioner to raise the inner fire and spread it throughout the body. During these practices, physiological responses are adapted to the body’s exposure to the cold: we will look at what scientists understand about the physiological mechanisms at work.

What are the mechanisms for adaptation to cold :

In the cold, living beings adapt the way their functioning to cope with energy losses. Mammals have developed several strategies, from hibernation to creating a layer of blubber to limit heat loss. For human beings, who have to maintain an internal body temperature of 36.8°C, this mainly means stepping up energy expenditure to keep warm. Our coat of skin and muscle is a light thermal insulator for a naked human in the cold. However, it seems to be sufficient: populations as diverse as the Yamanas (South America), the Bushmen (South Africa) and the Aborigines (Australia) lived for periods of 50 to 180 days naked, at winter temperatures of between +5 and -5°C.

All bodies follow the laws of physics: the amount of heat lost depends on a number of parameters, including thermal conductivity (the conductivity of water is 25 times greater than that of air), evaporation through perspiration and heat emission from the surface of the body through convection. Beyond a certain temperature, there is no more transpiration if the bodies are inert. Bodies cool down while heating up the environment in which they find themselves. If there is no external protection to prevent the heat produced by the body from spreading, it dissipates and heats up the outside environment. Hence the importance of covering up with hair or fur, which creates a surface layer that limits heat loss. When we get goose bumps, it’s our horripilation mechanisms that are at work to create a layer of air between our skin and the outside environment thanks to our hair cover. If we still have hair…

Another mechanism that reduces heat loss is the constriction of peripheral blood vessels (vasoconstriction). This is a first line of defence when the body is seized by the cold; this mechanism concentrates our heat in the centre of the body to protect the vital organs. Cold-induced vasodilation can also occur, involving paralysis of the muscles in the vessel walls and a hormonal change. This reaction makes it possible to remain in the cold by spreading heat to the extremities. It occurs earlier and lasts longer in people who are regularly exposed to the cold.

Every cell in the body is capable of producing heat. Below 35°C internally, the body is declared hypothermic: below 30°C, we lose consciousness. We know several mechanisms that produce extra heat to cope with heat loss. The contraction of skeletal muscles, whether voluntary (moving to warm up) or involuntary (triggering thermal shivering), helps to warm the body. The change in metabolism takes place thanks to several organs (liver, intestines, fat) and also several hormonal pathways that are at work: when the ambient temperature increases, the metabolism must decrease, and when the ambient temperature decreases, it increases to produce more heat. To regulate thermogenesis in the cold, brown fat is a central player.

Our bodies have several types of fat which are energy reserves. Brown fat is special in that it can produce heat tenfold. Unlike common white fat, which oxidises in the liver, brown fat oxidises its components wherever it is found, and most of the oxidation energy is transformed into heat. It is brown in colour because of the abundance of mitochondria, where the intensive oxidation of lipids takes place. It is brown fat that enables animals to swim in cold seas and survive winter sleep.

The large accumulation of brown fat prevents young mammals from cooling down excessively during a rapid change in temperature at birth. Although it is present in newborn humans, it was long thought to be absent in adults. However, thanks to new imaging techniques, these reserves have been actively studied in recent years. Regular exposure to cold converts white fat into beige fat. This browning of fats increases metabolism and therefore body heat. This metabolic mechanism regulates not only our temperature, but also inflammatory processes. The homeostasis of our energy system depends on immune cells located in these energy reserves. Brown fat therefore acts as an endocrine organ that communicates with all the other organs and has a profound impact on the whole body.

Impact of Pranayamas

Our body regulates physiological processes as important as digestion, blood circulation, respiration and thermogenesis via the autonomic nervous system. Together with the endocrine system, these functions regulate homeostasis, i.e. the constancy of our physiological values. This system is called autonomic, because you don’t need to think to digest, for example. The body takes care of these vital functions. The only conscious gateway to this internal clock is our breathing, because we can change its rhythm using the muscles of the rib cage. By relying on the muscular system, we can influence all the other players by altering the balance of the system.

Breathing is therefore a central mechanism for regulating thermogenesis. The air we breathe distributes oxygen to all our cells. At the heart of the mitochondria, which are specialised organelles, oxygen enables the production of a key energy molecule called ATP. During the chemical reactions that take place, heat is produced – this is the obligatory thermogenesis. When exposed to cold, the body will regulate this process differently, particularly in brown fat, and the proton gradient, which normally allows ATP to be formed, will dissipate, producing more heat.

The breathing techniques used by tummo practitioners are diverse: they all help to warm up to one degree or another. Two articles studying monastic practitioners in Tibet offer some interesting observations. The breathing techniques used include apnea phases accompanied by visualisations, in particular of flames gradually rising up to the skull. The result that seems particularly relevant to me is a direct correlation between the increase in body temperature and the duration of retention on full lungs (maximum time of 2 minutes and 50 seconds). The other observation that seems to me to be just as relevant, concerns the difference in temperature rise if practices are done with or without visualisation.  As you may have guessed, the impact of visualisations is clearly present, both in the differences in temperature and in the recordings of electrical traces in the brain.

What happens physiologically during the full-lung retention phases? We can imagine that there is less circulating oxygen (hypoxaemia), and also more carbon dioxide (hypercapnia). This hypercapnia could encourage better absorption of the available oxygen. If blood circulation is fluid, heat is transmitted without causing thermal lesions.

Another article of interest concerns practices based on the Wim Hof method: this work establishes the link between voluntary exposure to cold, coupled with meditation and phases of hypoxia, and the immune system. A group of novices was compared with a group of controls. The study shows that the people who underwent the training developed a very different immune response to those who were not exposed to the cold. Their bodies responded to the injection of a bacterial toxin, and their anti-inflammatory system was more effective, whereas in the control group the innate immune response to the injection was strong. Exposure to cold is already a serious option for treating autoimmune diseases.


Gérard BITTEL, Chief medical doctor at SRSAA, testified about Maurice :« I know Maurice DAUBARD for having examined and observed him. I found nothing in him, medically speaking, exceptional but the power of his will and his control. » When Maurice Daubard, condemned by medicine at the age of 18, found the mental strength to reprogram his life, he had no idea what his body was capable of. Years later, his physiological parameters were no different from those of ordinary mortals. Bending rather than breaking, the body has resources we don’t know about. The various stresses the body undergoes during exercise (cold, hypoxia) help to shape its changes and modulate its physiological responses. Regular practice allows the body to adapt and keep pace with the strength of the mind of the one who commits to the discipline. Daily outings and immersions allow us to rediscover our full capacities in a world where overprotection and comfort put our physiological adaptation capacities on hold. Similarly, we only marginally use our respiratory capacities: practice encourages us to develop our lung capacities, especially when the opportunity arises to go out in the mountains, far from urban pollutions.

Description of the figure:

This figure depicts adipose deposits, created using dynamic BioRender assets. The infant shows a widespread distribution of brown fat, whereas in adults, the areas where brown fat is found, are more limited (cervical, supraclavicular, axillary, peri-aortic, paravertebral, and inguinal regions). Fat cells are schematically represented on the right side of the figure, within the adipose tissue on the left and as individual cells on the right. In white adipose tissue, numerous pro-inflammatory immune cells are present, while their occurrence is rare in brown or beige adipose tissue. Moving from top to bottom, white, beige, and brown fat cells are observed: the number of mitochondria, responsible for ATP production (energy source) or heat generation (in brown fat), increases with the browning of the tissues. Additionally, the number of lipid droplets in each cell also increases; this fractionation allows for better metabolic activity of the cell.