Hot Yoga: A Systematic Review of the Physiological, Functional and Psychological Responses and Adaptations.

Background: Hot yoga is a collective term used to classify any form of yoga undertaken in warm to hot ambient conditions (≥ 25 °C). This study systematically reviewed the literature concerning hot yoga, with particular focus on acute responses to a single session and identifying prospective health benefits associated with physiological, functional and psychology adaptations following chronic practice.

Methods: The review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA), with searches performed across two main databases (PubMed and SCOPUS). Studies were included if they met the Population, Intervention, Comparison, and Outcome (PICO) criteria, were of English language, peer-reviewed, full-text original articles, and using human participants.

Results: Forty-three studies investigated the effects of hot yoga (both acute and/or chronic), totalling 942 participants (76% female). The most common method of yoga performed in hot conditions was Bikram (74%), followed by generalised hot yoga (19%), Hatha (5%) and then Vinyasa (2%). Typical session duration ranged 20-90 min and occurred within 30-52 °C and 20-60% relative humidity. Hot yoga training interventions consisted of 6-36 sessions, that were completed 2-6 times per week, over 1-16 weeks. Acute hot yoga increased body temperature and heart rate, but not the energetic demands when compared to other forms of non-heated yoga. Chronic hot yoga appeared to elicit cardiometabolic (e.g. body composition, lipid profiles and macrovascular function) and functional adaptations applicable for health (e.g., bone mineral density, balance and flexibility) as well as physical performance (e.g., submaximal exercise thresholds). Adaptations appear to occur without negatively impacting kidney function or sleep quality across healthy, sedentary and athletic populations. Hot yoga also presents promising, albeit inconclusive findings concerning the alleviation of psychological and affective disorders, and optimising markers of cognitive function. However, caution is advised as case studies report ill-health following hot yoga practice. Some literature lacks rigorous, high-quality experimental designs and sophisticated measurements that allow for mechanistic investigation.

Conclusion: Investigations into hot yoga demonstrate intriguing health and functional benefits. However, claims that hot yoga provides greater health benefits than other forms of yoga or traditional exercise are at present unsubstantiated. Studies describing beneficial effects of hot yoga often do not utilise robust experimental designs or methods that facilitate mechanistic insights. Hot yoga warrants further investigation as a tool to improve health and wellbeing. Researchers should consider the highlighted methodological limitations and recommendations to strengthen experimental work within future research.