Scientific studies show that Tummo yoga practitioners can use specialized breathing and meditative visualization techniques to generate internal heat and withstand extreme cold.
Papers [2] and [5] provide empirical evidence that practitioners of g-tummo meditation and associated breathing techniques can raise their core body temperature and maintain thermal regulation during extreme cold challenges. The remaining papers are either about different topics (cancer fatigue, pain, general meditation EEG, animal physiology) or do not refute the claim.