The findings of our research indicate that there are two distinct types of g-tummo practice, FB and GB, each characterized by different temperature patterns and neural (EEG) correlates. The temperature data bear out the practitioners’ claims that FB meditation is used to increase body heat, while GB meditation seems to facilitate the maintenance of an elevated body temperature. Indeed, reliable CBT increases were observed during the FB component of g-tummo practice, not only via FB meditation but also via FB vase breathing alone. However, the results of Studies 1 and 2 also suggest that that the neurocognitive component (“internalized attention” on visual images) of the MFB practice may facilitate elevation in CBT beyond the range of normal body temperature (into the fever zone), whereas the CBT increases during FB vase breathing alone were limited, and did not exceed the range of normal body temperature.
The results of the EEG analysis also indicate that FB and GB meditation were associated with different brain states in the practitioners. The EEG data showed significant increases in alpha and beta, and a marginally significant increase in gamma power during MFB, whereas during MGB only beta increased. Although the potential functional role of beta-band oscillations is not yet well understood, beta activity is associated with focused executive attention, and it seems to be related to the maintenance of one’s current sensorimotor or cognitive state 
. Thus, significant increases in beta, as observed in the present research as well as in the study by Benson et al 
might correspond to enhancement of attentional processes during both FB and GB meditation compared to their corresponding baselines. As for the increased gamma activity observed during FB meditation, studies on meditation consider it a signature of “samadhi” (deep meditative states of consciousness), but the regions of increase have varied, with recent studies reporting in some cases a frontally distributed increase in gamma 
, and in other cases an increase in gamma at posterior and occipital electrodes 
. Our data showed that gamma had the highest power at frontal areas during the FB meditation (however, the frontal distribution of gamma effects should be considered with caution as these high frequency changes might be confounded with activity of supraficial muscles and eye movements 
Of particular interest is the increase in the power of the alpha frequency band which was observed during FB meditation and its significant relation to the CBT increases. Contrary to an early view that alpha represented an idling process in the visual system, evidence has begun to accumulate in support of a role for alpha oscillations as a general inhibitory mechanism in the brain 
. Specifically, increased alpha activity in occipito-parietal areas has been linked to the successful suppression of visual input, which could disturb the maintenance of visual working memory representations 
. This is consistent with a more general observation that an inward shift of attentional focus toward mental activity (as in mental rotation or other visual-spatial imagery tasks) is typically accompanied by increases in posterior alpha power 
, suggesting that alpha might be working to decrease the distractibility of “external” sensory events to aid concentration on the mental activity. Similarly, meditation research has suggested that increases in alpha power correspond to “internalization of attention” (internally directed attention) during task performance as compared to baseline 
, which seems to be a plausible interpretation of our results. During FB meditation, practitioners are supposed to direct their attention to internally generated sensory information (visual imagery, heat perception). In contrast, there were no significant increases in alpha power during vase breathing alone, suggesting that these increases could be specifically attributed to the meditative component of the practice. We suggest that the increase in alpha power observed in our study reflects the meditators’ ability to focus attention on relevant internal states, specifically on visual images of flames and sensations of heat, while inhibiting external sensory information for extended periods.
The central finding of our study is that there are at least two separate factors that affect CBT increases during FB meditation. The first factor is related to the somatic component of the FB practice, specifically to the effectiveness of the vase breathing technique that affects the rate of CBT increase. Indeed, the results of studies 1 and 2 showed a significant correlation between the rate of CBT increases and apnea duration, during which the practitioners hold their breath while concurrently maintaining isometric muscle tension. The rate of these CBT increases was significantly higher than that due to circhoral rhythmic fluctuations in CBT, and it was similar to the rate of CBT increases of 0.02–0.17°C per min during the use of noninvasive systemic hyperthermia methodologies (e.g., immersing a patient’s body in hot water or wax, wrapping the body in a blanket or suit through which heated water is pumped, irradiating with IR energy) 
. The second factor is related to the neurocognitive component of the FB practice, specifically to the amount of “internalization of attention” or quality of meditative visualization, as reflected by increased alpha power during FB meditation. This factor seems to determine the rise time
of CBT, that is, how long the meditators are capable of continuing to raise their CBT beyond the range of normal body temperature without reaching an equilibrium phase. Indeed, the results of Study 1 showed that the greater the increase in alpha power achieved during FB meditation, the longer the CBT rise time, leading to higher CBTs.
Both factors work in conjunction to maximize the temperature increase. That is, the FB somatic component (vase breathing) causes thermogenic effects, while the neurocognitive component (meditative visualization) seems to be key for facilitating a sustained increase in body temperature for longer periods, possibly due to mitigating physiological mechanisms leading to heat loss. In systemic hyperthermia treatments, to prevent heat loss, and thus sustain CBT increases for longer periods, different insulation techniques are used (e.g., wrapping a patient body in reflective blankets, foil, or plastic films 
). In the case of FB meditation, one of the possible mechanisms preventing heat loss could be the mental imagery of flames and heat. Indeed, previous research has regarded mental imagery as a potentially effective technique in influencing peripheral body temperature, blood flow, and local vasodilation 
. Thus, it is possible that the mental imagery component of FB meditation minimizes heat loss, and thus prolongs the CBT rise time by similar mechanisms (changes in blood flow, reduced vasodilation). Without the accompanying meditative visualization, vase breathing might not be very effective and result in only limited CBT increases. At the same time, without an effective FB breathing technique, even small CBT increases, if possible at all, might require significantly longer meditation periods.
One of the questions arising from this study is why breathing and isometric exercises have been chosen by Tibetan meditators as a mean of thermogenesis, instead of dynamic movements (e.g., physical exercising, running). Different types of breathing and isometric techniques have been used for thousand years not only in Tibetan traditions but also in static holds in certain branches of yoga or oriental martial arts. What is common to all these practices is that they require focused attention on the internal mental states, which is difficult to do during rigorous dynamic exercise. Indeed, according to the g-tummo practitioners’ reports, FB meditation requires significant concentration, and cannot be performed in conjunction with running or even walking. For these reasons, during the ceremony of drying wet sheets, while walking outside, g-tummo meditators do not perform FB, but GB meditative visualization, which is much less effortful.
A limitation affecting the generalizability our findings is the small sample size due to the sacredness of the practice and difficulties in accessing g-tummo practitioners. Despite this limitation, we were able, for the first time, to document reliable CBT increases during the FB type of g-tummo practice, all within the slight to moderate fever zone, validating the legends of the extraordinary capacity of g-tummo meditators to elevate their body temperature beyond normal. However, the results also suggest that temperature increases during g-tummo meditation are neither solely a by-product of meditation nor its goal, but instead may be a means
to facilitate the achievement of “deep meditative states”. The g-tummo meditators may use the CBT increases as a vehicle to enhance their attention and focus their meditative performance (which may in turn facilitate a further increase in their temperature through meditative visualization). Future studies of experts in g-tummo meditation who are capable of elevating and maintaining elevated CBT may offer promising research insights and approaches to investigating mechanisms of CBT regulation. Because many variables underlying neuronal functioning (e.g., transport via ion-selective channels, amplitude and duration of single-unit spikes) are temperature-dependent 
, possibility of self-regulation of CBT may have a direct effect on self-regulating and maximizing neurocognitive activity. If future studies show that it is possible to self regulate CBT, by mastering vase breathing in conjunction with guided mental imagery without extensive meditation experience, it will open a wide range of possible medical and behavior interventions, such as adapting to and functioning in hostile (cold) environments, improving resistance to infections, boosting cognitive performance by speeding response time, and reducing performance problems associated with decreased body temperature as reported in human factor studies of shift work and continuous night operations