Over the last decade, I’ve come to realize how misunderstood the practice of yoga is particularly among those who’ve had little to no experience with it. Images of people sitting with legs crossed and eyes closed prevail in the minds of many while the physicality of yoga seems less understood. When I include yoga in my university lectures as a form of exercise, I sometimes get looks of confusion from students who haven’t tried it and I've even been asked if yoga is difficult enough to be considered a form of exercise. In addition, recent events in my own life have shed light on the fact that some people who, despite never having tried a yoga class, have well defined mental constructs about the practice to include people sitting in a room engaging in pagan rituals that are antithetical to religions outside of Hinduism. While there are spiritual aspects of the practice, one of the many things I love about yoga is its adaptability to individuals across diverse racial, ethnic, religious, educational, and socioeconomic varieties.
Yoga combines several practices, among them are the postures or asanas which can range in intensity from light (shavasana/dead man’s pose) to vigorous (surya namaskar/sun salutation sequence). Studies have shown that yoga can burn from 2 to 7 calories per minute depending on practice style. In general, yoga styles with consistent movement or flow from one posture to the next burn the most calories while yoga styles with isometric holds followed by breaks in between burn fewer. For instance, Bikram yoga, which deploys isometric muscle contractions to hold poses for 10 seconds to one minute, burns on average 3 calories per minute while vinyasa yoga, which includes consistent movement and smooth transitions from one posture to the next, can burn approximately 7 calories per minute. One cautionary note: don't rely exclusively on heart rate monitors to tell you how many calories you've burned during yoga as these devices can drastically overestimate caloric expenditure during yoga and other forms of resistance or strength training.
Heart rate monitors were designed to estimate calories based on exercises that reach a steady state in which the metabolic demands meet the metabolic production of energy for a prolonged period. Heart rate monitors are most accurate during repetitive movements performed over the course of 20 minutes or longer like walking, running, swimming, etc. Yoga poses cause heart rate to increase beyond what it typically associated with a given metabolic rate. This occurs due to the differences in blood flow during yoga versus cardio. In yoga, postures are held and these isometric contractions (usually of the leg muscles) drive blood flow the contracted muscles. This also happens during cardio workouts. However, the difference between yoga and walking briskly is that walking involves repetitive, short muscle contractions which help blood to return to the heart by applying intermittent pressure to the veins. This is called the “muscle pump.”
For the most part, yoga does not utilize this mechanism because the contractions are longer and typically, not repeated. This prolonged muscle contraction results in heightened sympathetic nervous system activation and a higher heart rate for a given metabolic rate. Bikram yoga is a good example of this as poses are held isometrically for 10 seconds to a minute and heart rates are the same as running while metabolic rates are similar to that of someone walking briskly with arms swinging. The heat in this yoga style exaggerates this response causing heart rates to be even higher than other yoga styles practiced in room temperature conditions. Thus, at the end of hot yoga, while heart rate may indicate 800 calories burned, the metabolic rate might only be at 300 calories burned. Keep this in mind if you're using yoga to burn calories and/or lose weight.
I published a paper last year with a doctoral student outlining the differences between heart rate and metabolic rates in yoga which can lead to misclassifications of intensities and caloric burn. To get a more accurate estimate of calories burned during a workout, metabolic carts are required to measure oxygen consumption. This provides a more accurate estimation of calories burned. In this paper, we reviewed studies that measured heart rates and oxygen consumption during various yoga styles and found that large differences in heart rates and measured metabolic rates exist. This was true for most yoga styles and the smallest differences or the style of yoga in which heart rate was most accurate in predicting calories burned was vinyasa. In general, heart rate monitors would likely be more accurate in vinyasa or power yoga and less accurate in Iyengar and hot yoga.
I'm including the average number of calories burned per minute below for various yoga styles. These numbers were calculated based on oxygen consumption values measured in research studies using metabolic carts. You can use this as a guide, but know that these numbers vary based on body weight (as body weight increases, calories burned also increase) and the quality of the practice. The fewer breaks you take or the longer you can hold the poses, the more calories you burn. This was documented by research which showed that experienced yoga practitioners burned more calories than those new to the practice. The temperature of the yoga room is not a factor here as calories burned are the same for room temperature and heated yoga classes. Increasing the temperature of the yoga room does, however, increase the heart rate response to the practice and could result in an overestimation of caloric expenditure during hot yoga when using heart rate monitors.
Here's the breakdown:
Beginner Hatha yoga ~2.2 calories/minute
Hatha yoga ~3.2 calories/minute
Ashtanga yoga ~3.2 calories/minute
Bikram yoga ~3 calories/minute
Standing Iyengar poses ~ 4.7 calories/minute
Surya Namaskar ~7.9 calories/minute
Vinyasa yoga ~7 calories/minute
I write this for clarification and not to discourage people from engaging in lower intensity practice styles. Even styles of yoga that burn few calories have been associated with some weight loss. We'll get into more about that later.
Larson-Meyer D. A Systematic Review of the Energy Cost and Metabolic Intensity of Yoga. Med Sci Sports Exerc. 48(8): 1559-1569, 2016.