Studying ten meditators of Tibetan Buddhism, a recent international research project provides solid evidence for centuries-old reports that through the advanced meditation practice Tummo, often referred to as “Inner Heat” or “Psychic Heat”, the core body temperature can be raised significantly.
The Tummo (also “g-Tummo”) meditation practice is an advanced form of meditation that has been transmitted in the Vajrayana (or Diamond Way) traditions of Tibetan Buddhism for the last 900 years. The spectacular outer sign of this meditation is that adepts are able to significantly raise their body temperature to an extent that they can melt the snow around them or dry wet blankets thrown over their naked body – at least this is how the traditional stories go. Already in the early 1980ies researchers from the Harvard Medical School set out to investigate these claims. Visiting three tummo practitioners in the foothills of the Himalayas, the researchers captured increases of peripheral body temperature (at fingers and toes) during this meditation by as much as 8.3 degree Celsius, apparently confirming the claims. However, later on criticism was raised concerning these results, for instance that the temperature range (22 – 33deg C) was in the normal body temperature range. Furthermore, similar increases have been observed merely as a result of changes to respiration and/or muscle contraction and, in consequence, cannot unequivocally be interpreted as a result of the meditation practice per se.
Recently, an international team of researchers from the US, Singapore and Germany again ventured to the Himalayas to take a fresh and more detailed look at the issue. This time 10 meditators (7 female) from the Nyingma and Kagyu meditation traditions of Tibetan Buddhism took part in the study. By considering two important aspects of this meditation practice, they were able to advance the understanding of this curious effect. Generally, Tummo meditation consists of a mental component, where certain images are called to mind, and a bodily, somatic component, where specific breathing practices, body postures and physical body movements are combined. Furthermore, these breathing practices can either be forceful or gentle. To shed light on what is taking place during this type of meditation, the scientists aimed to distinguishing between these different components. The meditators were asked to go through a sequence of four meditation conditions: 1) forceful breathing exercises without the mental component, 2) gentle breathing exercises without the mental component, 3) forceful breathing exercises combined with the mental meditation component and 4) gentle breathing exercises combined with the mental meditation component. At the same time the scientists recorded the electrical brain activity using electroencephalography (EEG) and the peripheral body temperature (at the fifth finger) and core body temperature (in the armpit).
So, what are the main findings? First of all, the study confirmed that the meditators were able to increase their core body temperature (in the armpit) significantly. Also increases of the peripheral temperature at the fingers was observed, but the authors argue that these may merely result from changes in the position of the hand during the practice rather be caused by meditation or breathing techniques. Interestingly, the increase in core body temperature only happened during the forceful breathing periods (with and without meditation), not during gentle breathing. During the latter periods the meditators maintained the increased temperature, though. This observation seems to confirm the explanation provided by the meditators that forceful breathing meditation is used to increase the body temperature, whereas gentle breathing meditation is used to maintain it.
But as there was an increase in core body temperature resulting from the forceful breathing with and without meditation, what’s the purpose of the meditation, of calling certain images to mind? Well, the data also show that the core temperature reached the slightly feverish range (of up to 38.5 C) only when forceful breathing was combined with meditation, whereas during forceful breathing alone temperatures, although elevated, remained in the range of normal body temperature.
The second part of this post will take a look at what happened with the brain activity, while these yogis were meditating.