Caution! Hot yoga may cause dizziness, hot flashes, nausea and headache during or after a lesson

Recently, many people use fitness clubs, sports gyms, studios, etc. for various reasons: for maintaining or improving health, losing weight, or other purposes. Statistics¹ released by the Ministry of Economic, Trade and Industry show an increase in users of fitness clubs, etc. between FY2016 and FY2018.

NCAC has conducted an online questionnaire survey on use of fitness clubs, sports gyms, studios, etc. among men and women in their 20s to 70s across Japan to ask their experiences of typical fitness programs and about sickness and injuries caused by the programs. Questionnaire results indicate that the percentage of respondents who got sick or injured due to hot yoga is higher than that of those who got sick or injured due to other programs.

PIO-NET² has received some inquiries and complaints about harmful incidents³ in fitness clubs, sports gyms, studios, etc. (hereafter called "fitness clubs, etc."). It has been reported that some people got sick during or after a trial lesson of hot yoga in yoga studios or fitness clubs. Harmful incidents caused by hot yoga account for a larger percentage of the harmful incidents caused by use of fitness clubs, etc. compared to other programs.

Therefore, NCAC decided to analyze harmful incidents caused by hot yoga registered with PIO-NET and conduct an online questionnaire survey about hot yoga to identify precautions for practicing hot yoga in yoga studios or fitness clubs, etc. Based on the findings, NCAC would like to issue a consumer alert and make a request to businesses concerned.

¹ The information is from data on fitness clubs in the report on statistics on specified service (Ministry of Economy, Trade and Industry) (Japanese page). On this report, fitness clubs include businesses which provide members with opportunities to practice and train sports in their facilities such as indoor swimming pools, training gyms, studios, etc. accompanied by instructors or trainers.
² PIO-NET is a database that collects information on inquiries concerning consumer affairs by linking NCAC with local consumer affairs centers and similar organizations across Japan via an online network.
³ "Harmful incidents" registered with PIO-NET refer to cases in which a product, service, or facility has caused harm (i.e. bodily injury, sickness or disease).

What is hot yoga

Yoga is a mind and body practice with a 3,000-year history, which originated in ancient India. In recent years, Yoga has been adjusted to modern lifestyle and accepted by many people as a mental and physical practice.⁴ There are various yoga postures: seated and standing poses, chest-opening poses, twists, etc.

Yoga practiced in hot and humid conditions is called "hot yoga". The website "Japanese Integrative Medicine" run by the Ministry of Health, Labour and Welfare states as follows: "Hot yoga is practiced in hot and humid conditions at the temperature around 40 degrees Celsius. Such conditions put extra stress on human bodies. When practicing hot yoga, people need to take safety measures."⁵

⁴ Source: Yoga (e-Health Net) (Japanese page) on the website of the Ministry of Health, Labour and Welfare
⁵ Source: Yoga (Japanese Integrative Medicine) (Japanese page) on the website of the Ministry of Health, Labour and Welfare

Information from PIO-NET

PIO-NET has registered 833 harmful incidents (sickness or injuries)⁶ caused by use of fitness clubs, etc. since FY2015. According to the breakdown of the incidents by fitness programs, incidents related to hot yoga amount to 165 (about 20% of the total), representing the highest percentage.⁷

⁶ Data registered from April 2015 through the end of March 2020, excluding inquiries referred from local consumer affairs centers to NCAC
⁷ The figures were calculated specially for this report.

The breakdown of the harmful incidents caused by practicing hot yoga in fitness clubs, etc. (165 cases in total, excluding unknown cases) shows:

Women account for 99% of the total.
People in their 40s account for 48 (30%), representing the highest percentage among all the age groups.
81 persons did not see a doctor, which account for 64% of the total, the highest percentage.
112 persons (70%, the highest percentage) suffered from hot flashes, nausea, headache, etc. The symptoms fall under the category of "other illnesses and various symptoms".

Sampling of inquiries and complaints

[Case1]: During a trial lesson, I felt sick and vomited.
[Case2]: In the evening of the day of a trial lesson, I had a headache and a high fever of 40 degrees Celsius.
[Case3]: I signed up for a hot yoga course after a trial lesson. Every time I practice hot yoga, I feel sick and have a bad headache.
[Case4]: During an advanced lesson which I didn't intend to join, I felt sick. Since I didn't know whether it was appropriate to have myself excuse during the lesson, I had my patience and kept practicing. After the lesson, I vomited.
[Case5]: After a trial lesson, I signed up for a hot yoga course. Just to be sure, I told an instructor that I had a condition of migraine before signing up. Next day, I had a terrible migraine and vomiting.
[Case6]: I have been listless for a few days after attending a trial lesson. There was no mention about the possibility of dehydration before the trial lesson.

Hot yoga environment and lesson time

Online description

In order to find out conditions for hot yoga such as room temperature, humidity and the length of a lesson, NCAC checked websites of 21 businesses searched through Google and Yahoo!JAPAN with words "hot yoga" which run fitness clubs, sports gyms, etc. and have two or more facilities for hot yoga classes in June 2020.

Survey results⁸ show that the most businesses state that the room temperature is set at 38 degrees Celsius and the room humidity is set at 65% during hot yoga classes. The most common lesson time is 60 minutes.

⁸ The room temperature and humidity during lessons are written in reference to 12 businesses which mentioned them online. The lesson time is written in reference to 20 businesses which mentioned it online.
⁹ Some businesses state that the room temperature and humidity during lessons are not kept as before and sometimes become lower due to room ventilation as a preventive measure against COVID-19.

Guidelines for heatstroke prevention vs hot yoga environment

A comparison of "Guidelines for heatstroke prevention in daily life"¹⁰ by the Japanese Society of Biometeorology and descriptions on the websites of the 12 businesses shows that the most common hot yoga environment of temperature 38 degrees Celsius and humidity 65% falls under the category of "dangerous".

¹⁰ Source: "Heatstroke prevention in daily life" released by the Japanese Society of Biometeorology in May 2016

Questionnaire survey

Number of attendants and those who got sick or injured in each program

NCAC have questioned about 10,000 men and women in their 20s to 70s across Japan who have used fitness clubs, sports gyms, studios, etc. (9,599 respondents).

Of 9,599 persons who have used fitness clubs, sports gyms, studios, etc., 1,603 persons (17%) have experienced hot yoga. About 20% of the 1,603 persons have got sick or injured due to hot yoga.

Sickness and injuries caused by hot yoga

In order to clarify sickness and injuries caused by hot yoga, NCAC questioned 200 persons among respondents who answered "I have got sick" and/or "I have got injured".

Details of hot yoga classes, and experience of other types of yoga

About 70% of the 200 respondents attended hot yoga classes in yoga studios.
About 60% of the 200 respondents experienced other types of yoga before joining hot yoga classes. About 60% of the 200 respondents did some exercise once a week or more in addition to hot yoga.

Instruction and explanation before a hot yoga lesson

About 30% of the 200 respondents were asked their health condition on the day, chronic illness or medical history before each lesson.

Timing of sickness and details of injuries

175 respondents have got sick due to hot yoga. Their symptoms include "dizziness, lightheadedness", "hot flashes, heat", "nausea, vomiting", "headache", etc. About 50% of them answered "I quit attending hot yoga classes because it made me sick".
About 90% of the 175 respondents got sick "during the lesson" or "soon after the lesson". Some others got sick "several hours after the lesson" or "on the next day of the lesson or later".
Of those who got sick during the lesson, about 20% did not stop practicing hot yoga till the end.
Questions to 32 respondents who got injured revealed that the most common injuries were "pain in the neck or the low back" and "joint pain, dislocation, sprain".

Advice for consumers

According to the Guidelines for heatstroke prevention in daily life, conditions for hot yoga fall under the category of "dangerous". PIO-NET has received some inquiries and complaints about harmful incidents caused by hot yoga such as dizziness, hot flashes, nausea, and headache.¹¹ Before joining a hot yoga class, confirm details of the class and the lesson time. If you have any chronic illness or pre-existing condition, carefully consider whether or not you join a hot yoga class.
Online questionnaire survey results have revealed that those who exercised once a week or more also suffered symptoms such as dizziness, hot flashes, nausea, and headache due to hot yoga. During a hot yoga lesson, stay hydrated and take a break in a cool place.
According to cases registered with PIO-NET, some people got sick several hours after the lesson. Take care of your health even after practicing hot yoga.

¹¹ Reference for contractual troubles related to fitness clubs, etc.: Beware of contractual troubles related to sports gyms, etc. (e.g. "I cannot cancel the contract," "Cancellation fee is expensive") (Japanese page) released on October 11, 2018

Request to businesses

It has been reported that some people got sick due to hot yoga. NCAC requests businesses concerned to take further safety measures, for example, paying attention to each attendant during hot yoga classes in addition to asking chronic illness, medical history and physical condition on the day.

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