Table 1: Characteristics of Bikram trials reviewed.

Study identificationCountrySample sizePopulationSex (M/F) Mean age (years) Treatments Control conditionsTrial duration (weeks) Outcome measuresMain findings
Major inclusion criteriaMajor exclusion criteria

Randomized controlled trial
Tracy and Hart, 2013 [4];
Hart and Tracy, 2008 [3]
USA21Apparently healthy, relatively sedentary (<2 hours/week purposeful exercise <moderate intensity, one active subject in the yoga group and one in the control group)Medical condition or medication that could influence participation or dependent measures and yoga practice within 4 months prior to studyM/F27Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, 3 classes/week. Average attendance 22.5 classesNo treatment8Physical strength (isometric deadlift, hand grip strength, MVC of knee extensors/elbow flexors, concentric/eccentric steadiness), functional fitness (sit-and-reach and shoulder flexibility, single-leg balance), cardiovascular fitness (VO2max, resting BP), body composition (fat mass and lean body mass using DEXA)Increased isometric deadlift strength ( between groups), increased knee extensor MVC within and between groups (, ), increased balance yoga group (), increased back/hamstring flexibility ( between groups), trend towards significance for shoulder flexibility and for decreased fat mass in yoga group ()

Controlled trials
Hunter et al., 2013 [9]USAYoung = 14
Older = 15
Sedentary (<2 days/week physical activity for past 6 months), lean participants BMI 18.5–24.9 and obese participants BMI >30Smoking within last 6 months, uncontrolled diabetes, personal history of stroke, prior myocardial infarction, and known coronary heart diseaseM/FYoung = 32
Older = 46
Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, 3 classes/weekNo nonyoga control8Glucose tolerance (75 g GTT, FPG) body composition (fat mass and lean body mass using DEXA, BMI, body mass)Increased glucose tolerance in obese subjects (), decreased body mass () and BMI () in obese subjects
Hunter et al., 2013 [8]USAYoung = 24
Older = 18
Sedentary (no habitual activity over last 6 months), young participants aged 18–39 and older participants aged 40–70Pregnancy, uncontrolled hypertension, infection within last 4 weeks, renal disease, adrenal or endocrine tumours, prior myocardial infarction, known coronary heart disease, chronic heart failure, personal history of stroke or cardiac arrhythmias, diabetes, heat intolerance, and cardiovascular or hormone replacement therapy medicationsM/FYoung = 30
Older = 53
Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, 3 classes/weekNo nonyoga control8Arterial stiffness (carotid artery compliance, carotid pulse pressure), body composition (body mass, fat mass using DEXA), blood glucose measures (HbA1c, FBG, plasma insulin, HOMA-IR), cardiovascular health (total, LDL, and HDL cholesterol, triglycerides, BP), flexibility (sit-and-reach)Increased carotid artery compliance in young adults (), decreased arterial stiffness in young adults (), decreased plasma insulin and HOMA-IR in older group (), decreased total and LDL cholesterol in older group (), decreased total and HDL cholesterol in young group (), increased flexibility in both groups ()

Uncontrolled trials
Hewett et al., 2011 [5]USA51NRBikram yoga practice at all in past 3 months and long term within last 2 years and medical conditions that did not pass medical clearance for participationM/F32Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, ≥3 classes/week. Average attendance 28.6 classesNo control8Psychological health (perceived stress, mindfulness), cardiovascular fitness (predicted VO2max, RHR), physical fitness (sit-and-reach and shoulder flexibility, single-leg balance)Increased mindfulness (, ), perceived stress (, ), predicted VO2 (, ), flexibility (, ), balance (, ), correlation between mindfulness and perceived stress (, ), and mindfulness and resting heart rate (, )
Kudesia and Bianchi, 2012 [6]USA13Apparently healthy, were planning to start or already practicing Bikram yogaMedical problems or medications that might interfere with sleep monitor’s algorithm (e.g., epilepsy)M/F35Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, 2–12 classes/14 daysN/A2Sleep architecture (time spent in each sleep-wake stage, duration of awakenings)Decreased duration of awakenings on days of Bikram yoga practice (more rapid return to sleep after nocturnal awakenings)

Longitudinal study
Sangiorgio et al., 2014 [10]USA9Female (30–59 y), certified Bikram yoga instructors, practicing minimum 3 years, good physical healthNRF51 (at 5-year follow-up)Continued practice of Bikram’s beginner’s yoga class (room heated to 40°C, 40% humidity, same 26 asanas and breathing exercises each class), 90 min/class, 3+ classes/week for 5 years. Continued teaching of Bikram yoga during 5-year period.N/A5 yearsBone mineral density (using DEXA to measure at the spine and hip, and total body)Premenopausal women at follow-up showed mean increased BMD at the femoral neck (6.6%  ±  5.5%), total hip (2.0%  ±  3.8%), and lumbar spine (1%  ±  4.7%). Postmenopausal women at follow-up showed mean decrease in BMD at the femoral neck (−6.0%  ±  6.6%), total hip (−8.1%  ±  6.1%), and lumbar spine (−5.6%  ±  9.1%).

Cross-sectional and acute studies
Pate and Buono, 2014 [28]USA26Healthy adults (18–57 y), current Bikram practitioners with varying levels of experience (<20 classes and >20 classes)Positive responses on PAR-Q and pregnancyM/F33N/AN/AN/AAcute response to Bikram yoga session in temperature controlled chamber (40°C, 40% humidity) including metabolic (VO2), cardiovascular (HR), and sweat rate responseAverage overall VO2 9.5 mL/kg/min, average overall intensity 2.9 METS, average overall EE/session 286 kcal (179–478), and higher relative EE for more experienced practitioners
Abel et al., 2012 [7]USALE = 17
HE = 14
Apparently healthy adultsSigns or symptoms of heart, pulmonary, or metabolic diseaseM/FLE = 44
HE = 38
N/AN/AN/APulmonary function (FVC, FEV1, FVC/FEV1, PEFR, MVV), cardiovascular fitness (VO2max, RHR, BP)Weak correlation of Bikram experience with FEV1 () and with % predicted FVC ()
Fritz et al. 2013 [29]USA19Current Bikram yoga practitioners attending 2 classes/week for at least 1 yearNRM/F30N/AN/AN/AAcute response to Bikram yoga session in temperature controlled chamber (40°C, 40% humidity) including metabolic (VO2), cardiovascular (HR), and thermal (internal temperature) response and RPEAverage VO2 13 mL/kg/min, average RPE 4.5, average HR 134 BPM, average overall intensity 3.7 METs, overall EE 333–459 kcal, and elevated core temperature within safe range (max 101.6°F)

BMI, body mass index; BP, blood pressure; BPM, beats per minute; CV, coefficient of variation; DXA, dual-energy X-ray absorptiometry; EE, energy expenditure; EEG, electroencephalogram; F, female; FEV1, forced expiratory volume in one second; FPG, fasting plasma glucose; FVC, forced vital capacity; GTT, glucose tolerance test; HbA1c, haemoglobin A1c; HE, high experience; HOMA-IR, homeostasis model of assessment of insulin resistance; HR, heart rate; LE, low experience; M, male; MRI, magnetic resonance imaging; MVC, maximal voluntary contraction; MVV, maximum voluntary ventilation; NR, not reported; PAR-Q, physical activity readiness questionnaire; PEFR, peak expiratory flow rate; RHR, resting heart rate; RPE, rate of perceived exertion; VO2, volume of oxygen uptake.