Moments, Arms, & Moment Arms

In a perspective article on scapular stabilization, the concepts of moments and moment arms came up. My fuzziest understanding is that they are related to rotation around a joint. And angles. And math. Usually, I ignore such words and cleave to the bigger picture. But scapulae are enticing black boxes to me and in the case of this article, moments and their arms seemed crucial to an understanding of the author’s theory of departure. This was the sentence that tossed me over the cliff: “Therefore, equal muscle forces are not mandatory – and could be clinically undesirable – because the muscles have different moment arms and thus different mechanical advantages for causing angular rotation in the joint.” I knew I needed help.

Historically, when I’ve tried to educate myself about biomechanical stuff (moments, arms, angles, etc.), my eyes glaze over and I hear this sound. Its hard to find someone writing about these biomechanical concepts in language that I can apply to my own understanding of yoga postures. So I reached out to my friend Christine McSween to help me understand. And that’s revisionist. Actually, Christine engaged with me in a Facebook group around this topic and we agreed to turn it into an educational interview for our group and the world.

Christine was drawn to the spiritual and mindfulness aspects of yoga in the beginning, but with further study she learned how amazing the physical body is along with a realization of the need for more education. With increased fervor, in 2015, she began pursuing a kinesiology degree at the University of Calgary with a focus in biomechanics. She teaches yin yoga, gentle yoga and Restorative Exercise.

Here is our conversation.

MM: I have a hazy understanding of a moment arm, but could not verbalize it well enough to get off the island. Can you give me the words?

CM: Can you let me know your definition first? I want to see what you’re working with!

MMI can’t! I don’t have my own words. My understanding is hazier than I thought. Sigh.

CM: I want to work through this a bit. Do you have a clearer understanding of a “moment” than the “moment arm”?

MM: Sadly, no. I clearly need a biomechanics lesson.

CM: Ok, I know where to start then!

CM: I’m going to draw a picture.

momentarm2

CM: As you can see in the picture, we have isolated the bicep as the force that will lift the forearm (of course we know this is super simplified).

The force in the bicep creates a moment – or rotation about the elbow joint (or axis of rotation). Because the bicep is only 5 cm down the forearm, it needs to create a LOT of force to lift the forearm. This is because the mass of the forearm is also creating a moment about the elbow joint due to gravity.

MM: (interrupting): Could you say a moment is any rotation about a joint? Does that mean there are an infinite number of moments for a given joint?

CM: YES!

CM: Often in biomechanics we talk about “resultant moments” which is the resultant effect of all the moments about a joint. If the resultant moment is not zero (can be negative or positive), then we have a rotation or movement. I will say though, that the center of mass (COM) is a resultant force, since we know gravity impacts the whole arm

MM: First things first. Can you give me an example of a resultant moment being negative or zero with no rotation/movement? And what is the significance of COM being a resultant force.

CM: When a resultant moment is zero, you have an isometric contraction. There are moment’s occurring, but because they cancel out, the resultant moment is zero. This is how we first learn to calculate forces from moments in physics and biomechanics classes. We assume static equilibrium (no movement) to simplify the calculations.

In our case the system of interest is the forearm. If the forearm rotates towards the upper arm (counterclockwise), this is a positive moment. If the forearm rotates clockwise (extending the elbow), this is a negative moment. Of course, if we flipped our picture around, it would be the opposite.

We use a resultant force for the COM because otherwise we would have to calculate every cell’s mass and every cell’s moment arm, which would have us calculating for days, or weeks, or years. Not ideal! Instead, we can actually measure the weight of the whole forearm, and measure one moment arm to the COM of the forearm. Yay! Only one calculation.

MM: Let’s move on to moment arms.

CM: Now a moment arm is the perpendicular distance from the line of force application to the axis of rotation. Or…the moment arm is the distance from the elbow joint, to the attachment of the bicep, as it relates to the angle of the bicep.

MM: I prefer the latter. And would another moment arm be the distance from the elbow to the hand to account for the mass of the forearm?

CM: No, usually the moment arm is to the center of mass. So probably somewhere in the middle of the forearm. If the hand is holding a weight, then there is another moment arm to the hand.

MM: Let me get this straight. Using the picture above, one moment arm is from the elbow joint to where the bicep attaches on the forearm. Another moment arm is from the elbow joint to the center of mass of the forearm, which is likely near the center of the forearm – but this is only if nothing is being held in hand, I assume. Yet another moment arm would be from the elbow joint to a dumbbell, if one were being held. Eh?

CM: You bet! Just remember the moment arm is in relation to the angle of the applied force. If the forearm is at 90 degrees (like in our picture), then the moment arm would be length from the elbow to the dumbbell. However; this will not be the case if the forearm is at an angle. The applied force is no longer perpendicular.

CM: An example of how awesome our body is with creating more efficiency is our beautiful patella!

MM: What is/are the moment arms in this animation?

CM: When there is no rock, there is a very tiny angle between the elastic and the stick, which leads to a very tiny moment arm. So more force is needed for rotation. When there is a rock, the angle is much larger, leading to a larger moment arm, so less force is needed for the same amount of rotation.

MM: We are looking at the angle between the “femur” and the “patella,” yes?

CM: No, the patella and the tibia. The femur isn’t within our “system of interest” in this case.

MM: Dammit.

MM: Ok, so we have the force of the muscle and an external force like gravity or a weight creating individual moment arms. Are these opposing forces? Are there others?

CM: They aren’t quite opposing forces, as they are opposing moments. The bicep is creating a positive moment, while the COM, and a weight in the hand would be producing negative moments. This concept might be more simple if you think about a balanced teeter totter. On either side of the fulcrum you have equal forces in the same direction. BUT the moment arms are opposing, creating opposite moments. Does that make sense? Because our bodies are so wonderfully complex, you could add as many forces as you like, or make it is complicated as you like. And this is why resultant moments are used so frequently. When you add everything together, all the moments and forces, what will happen?

MM: I’m hoping that is a rhetorical question! I suppose it would determine if and how movement happens around a given joint or all joints….

MM: I’m guessing that moment arms are more straightforward, when we are talking about hinge joints like elbows, right? But more complex if we are talking about, say, the scapula?

CM: It would still be the same process, but yes, more difficult to quantify merely because the moment arm would be so small, because of the angles involved.

MM: Wouldn’t there be multiple forces applied to a scapula since it has multiple muscular attachments, moves in multiple planes, and is involved in multiple joints? What is the relationship ship between multiple moment arms and movement in a joint as complex as the shoulder complex?

CM: Simply, this complex structure allows for almost infinite variability in movement. Which logically, makes sense. If our shoulders are “less stable” to allow for more movement, it would make sense to have a variety of options in order to make those movements happen.

MM: So what? Who cares? How is this useful information for a movement practitioner?

CM: Understanding moments and forces allows us to be creative with our cueing and provides a greater understanding of alignment. Plus, we can see how anatomy impacts our biomechanics. In my 21 Day Biomechanics Challenge , I will be using my friend and I as an example. 

MM: I thought it might be illuminating to bring in a yoga pose for you to identify forces and moment arms. I give a shout out to this Yoga Stick Figure from Justine Aldersey-Williams. I’ve been using her clever illustrations in my teaching materials for several years now. You can download over 200 images from her Etsy store for just $5.

moment_trik

Image: Justine Aldersey-Williams

MM: Let’s take one of these arrows that you’ve drawn on the figure and tell me what’s going on.

CM: Consider this a static triangle, so the sum of all the moments equals zero. And we want to know the effect of placing the hand on the ground/leg or block vs. having it hover. To remain static, how would the resultant forces of the back leg and obliques change? If the hand is hovering, the resultant forces in the leg and obliques would have to increase to prevent the torso from rotating clockwise towards the ground. When the hand is pressing against something, it provides an opposing force that will rotate the torso counterclockwise, and the resultant forces in the back leg will be smaller. You can try this yourself by practicing both situations. What takes more effort?

MM: That’s fantastic!

MM: I have one final question. If we are biotensegrity systems (and not lever systems) with fascia deeply and exquisitely  investing our connective tissues, how should this interconnectivity influence how we think about moments and moment arms in movement?

CM: This is a question I have been struggling with for a couple years now, trying to put my thoughts to words. I must emphasize that my answer to this question will probably evolve over time as I learn more.

Although yes, we are not built like traditional buildings, and are amazingly adaptable tension systems made for mobility, this does not negate the importance of traditional biomechanics. Neither system is wrong, they are just different models, or filters by which we can understand the physical world.

And I think you can combine these models. If you take a tensegrity structure, and expose it to an external force, a moment may still be created. That entire structure might rotate. Or deform. Or translate. There are a number of options.

I think people can assume that this model will destroy the old, but there is not much evidence for that at this time. Biomechanics researchers understand that the body is not a bunch of simple levers. Load is distributed throughout the structure – like tensegrity! But this doesn’t mean that classical biomechanics has no place. Especially when we are starting to learn these concepts. As you study further into biomechanics, you must take into account our biology – how biological tissues respond to forces.

Muscles DO produce force to cause rotation. So we need both models to understand what’s happening in the body as we move. Levers exist, and yet we are this system of tension and compression. As we lift the forearm, not only the muscles such as the bicep, and brachialis lift the forearm, but the triceps create tension and can also contribute eccentric forces, while muscles in the shoulder and chest create stability.

The biotensegrity model informs classical biomechanics, and helps us question our assumptions, but it does not negate the model. If I may quote Jules Mitchell, “Such theories provide a foundation for forward and radical thinking, but are prone to become “buzzwords” which dilute scientific understanding among the mainstream.”

So, why does this stuff matter? The article that started this conversation shows a fantastic combination of questioning classical biomechanics, and informing it with the biotensegrity model. But the basic elements of moments and forces don’t disappear. We still need to understand these concepts to help us move forward.

“The key point is that stability is context specific, depending on the system and the task being performed.” I think this statement could be applicable to many other areas of the body.


And there you have it. A big thank you to Christine for her generous time in taking complex biomechanical concepts and explaining them in the concept of yoga.

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Yoga for Perimenopause

From time to time, I share postures included in published yoga research. I’ve used such lists to inform my own sequencing, both in group classes and when working privately with clients. Today’s share is a list of asanas that were included in a yoga protocol for a study of perimenopausal women. I’m not providing analysis or evaluation of the research, just the poses. In this study, 216 women were assigned to either a yoga group or an exercise group. The intervention was practiced for 45 minutes every day for 12 weeks.

Perimenopausal women have been shown to have increased blood sugar levels and may be at higher risk for diabetes and metabolic syndrome. It should go without saying that perimenopause is a stressful physiological state in women. Thus, the study measured blood sugar and stress hormone levels before the intervention period and again, after 12 weeks of intervention.

The study found yoga to be as beneficial or better than exercise at improving fasting blood sugar and stress hormone levels, with participants reporting calming effects of yoga practice and a general feeling of wellness.

And here, as promised, are the postures practiced in the yoga group. I’ve provided a visual of each asana using Yoga Stick Figures from Justine Aldersey-Williams. I’ve been using her clever illustrations in my teaching materials for several years now. You can download over 200 images from her Etsy store for just $5. Inconsistencies in naming & spelling of yogasana across yoga styles & teachers is to be expected, but these illustrations capture the basic shape of each pose. You’re welcome!

Asanas & approximate time held

Swastikasana (auspicious pose) 2 min

siddhasana

Vajrasana (thunderbolt pose) 2 min

virasana

Suptavajrasana (reclined Thunderbolt Pose) 2 min

supta-virasana

Tadasana (Mountain pose) 2 min

tadasana

Trikonasana (Triangle pose) 2 min

trikonasana

Parsvakonasana (extended side angle pose) 2 min

parsvakonasana

Paschimottasana (seated forward bend) 2 min

paschimottanasana

Purvatanasana (seated back arch) 2 min

purvottanasana

Janushirshana (head to the knee pose) 2 min

janusirsasana

Pavanamuktaasana (wind relieving pose) 2 min

apanasana

Bhujangasana (cobra pose) 2 min

bhujangasana

Shalabhasana (locust pose) 2 min

salabhasana

Dhanurasana (bow pose) 2 min

dhanurasana
Vakrasana (twisted pose) 2 min

marichyasana

Padottanasana (wide-legged forward bend) 2 min

pras_padottanasana
Shavasana (corpse pose) 5 min

savasana

Pranayama(breathing exercises)

Anuloma-viloma (alternative nostril) 5 min

Suryabhedana (right nostril) 5 min

Sheetali (through tongue) 2 min

Bhramari (honey bee sound during exhalation) 2 min

Namaste, Michele

More Exercises for Pronated or Flat Feet

I contend that barefooting is the best and most natural way to have strong, mobile, and healthy feet. But it takes time to transition to an unshod or minimally shod lifestyle and not everyone wants that. So, I make a point to keep up with and share biomechanics- and physical therapy-informed clinical research on foot health. In the past, I’ve suggested you add the short foot exercise for arch strengthening to your foot health protocol. I use it regularly with my clients and in my FootLove Workshops.

Here is another foot exercise to consider for pronated and flat feet and hallux valgus – the condition that leads to bunions. The Toe Spreading Exercise is easy to do. I suggest you do it standing, but you could also do it seated with your hips and knees flexed to 90 degrees. I use a yoga mat under my feet for comfort.

  1. Stand with your feet pelvis width distance apart and facing forward.
  2. Spread the toes on your right foot as far apart as you can. If you are unable to spread your toes on your own, reach down with your hand and help to spread them.
  3. Raise your heel
  4. Over a slow count to 5, lower your heel to the ground.
  5. Hold in that position for 5 seconds
  6. Relax the foot
  7. Some protocols have you repeating this up to 100 times! But you might just want to start with 5 or 10 reps. Repeat with your left foot.

A recent study suggests that along with the toe spreading exercises,  you also strengthen your gluteus maximus, commonly referred to as your butt. Your big butt muscle is responsible for externally rotating your hip joint, and a strong one is thought to alter alignment of the lower extremity, thus reducing foot pronation. The authors found that the exercise most effective for a strong butt is performed in a prone position (lying face down) by slightly lifting the knee while maintaining the hip joint in external rotation and the knee joint at 90° flexion.

I bring this exercise into the yoga world as a unique modification of salabhasana aka locust pose. Or, you could think of it as a hybrid between locust and bow poses. The study protocol called for 3 sets of 20 repetitions of single leg lifts. I think you could explore fewer reps of double legs and longer holds.

Namaste, Michele

Picking Strawberries Stacked the Best Yoga Practice of My Life

Internationally renowned biomechanist Katy Bowman coined the phrase “stack your life.” Instead of making errands, movement, family/friend time, studying, entertainment, etc. discreet events, each taking up precious amounts of time, you perform these experiences together, essentially stacking your life. For instance, today my partner and I walked (movement/exercise, family time). Partway through our walk, we listened to a podcast (edu-tainment). Our walk had a task associated with it – dropping off an item at a friend’s house (errand done!, friend time); and a destination -our local coffee shop, where we studied, chatted, and enjoyed seeing several regulars (community, family, coffee time). Infused in a stacked life are often values held dear – decreasing an environmental footprint by not driving, being an observing presence in our neighborhood, adding to its vibrancy by our street presence, and supporting a local business and the community it gathers. Stacking our lives in this way is rich and rewarding and does not carry the weight of feeling like there is not time to get done what we need.

I recently spent two hours picking strawberries and found it to be a another perfect way to stack my life. I stacked family time, support of a local farm, share in a harvest, participation in the agricultural bounty of our valley, securing food, and the best yoga practice of my life. Yoga? Yes, yoga.

For two hours, I organically cycled through countless variations of malasana (squat), uttanasana (forward fold), virasana/vajrasana (sitting back on heels), bharadvajasana, Yin’s deer pose, lunges, sukhasana (seated cross legged), ustrasana (camel), snippets of surya namaskar (sun salutations), and asanas for which there may be no name.

Obviously, I didn’t capture this on video, but here is a 15 second re-enactment in time lapse.

And listen to Katy’s podcast on stacking your life. It’s been one of the most inspiring podcasts that I’ve listened to this year.

strawberryyogastill

Namaste, Michele

Alphabet Feet

Our feet respond well to varied movements. I talked about this last year in my weird feet post. This is a spirited yogasana foot exercise mash-up that moves your foot and ankle through countless ranges of motion and is probably good for your neurobiology as well.

I taught this dynamic asana/exercise in my yoga class this morning. It’s kind of impossible for this not to devolve into silliness, so you might keep that in mind if you are a teacher using this in your class.

alphabet_feet

  1. Sit on the floor (could also be done in a chair) with your legs extended in front of you.
  2. Hand options: either place your hands alongside your hips to support you in sitting upright; or interlace your hands and press your palms away from you.
  3. Bend your knees and place the soles of your feet on the floor in a pre-boat pose position.
  4. Lift your right foot off the floor.
  5. Using your best “handwriting,” slowly trace the letter A (print, cursive, all caps or small – doesn’t matter) in the air with your right foot, using your big toe as a marker. Move mainly at the ankle joint and less so at the knee and hip. Take a breath.
  6. Trace the letter B. Breathe in, breath out.
  7. Trace the letter C. Full breath cycle.
  8. Trace the entire alphabet, pausing a breath cycle between letters.

In my class, we traced A-M with the right foot, took a forward fold and then N-Z with the left foot, which for most of the class was the non-dominant foot and quite a bit more challenging.

I like doing this in boat pose with hand stretches because it allows more of my muscles to participate. Come up with your own variation and share it with me.

Here is my video of A-G.

Learn more exercises for your feet from my teacher renowned biomechanist Katy Bowman with these brilliant exercise videos that you can stream or download to view as often as you like for just $5 each!

Toes-and-Calves-Screenshot-300x300

Schoolhouse Series: Toes & Calves

UnDuck-Your-Feet-Screenshot-300x300

Schoolhouse Series: Unduck Your Feet

Namaste, Michele

 

Yoga Protocol for Balance for Poststroke Pilot Study

I read the full text of a few yoga studies each week. As a former research librarian with the current salary of a yoga teacher & blogger, I rely on free full-text sources, and when those are not available, I lean on former colleagues to help a girl out. Shh. Don’t tell.

This morning, I read the study “Poststroke balance improves with yoga: a pilot study,” which found significantly improved scores for balance in the study group receiving a group yoga intervention, with those who completed yoga even crossing the threshold of balance impairment and fall risk. “Because of improved balance, participants increasingly attempted new activities in different and more challenging environments and were aware of potential fall risk but grew confident in maintaining their balance.” Incredibly life changing for these participants and potentially for our stroke clients.

Granted the sample size was small (47), there were methodological gems with this study:

  • Participants were randomly assigned to the study & control groups
  • Two yoga groups and a wait-listed control group were included
  • Attrition/retention was reported

I am always curious to see which asanas are included in these studies, so that I can make more evidence-based choices for when I work with clients, who are dealing with similar health related issues. It is frustrating that many studies do not provide details on the yoga interventions used. But, to my delight, this inspiring study included in its publication an outline of it’s yoga protocol!

I hope you find it helpful as you craft your next balance-themed class or private session – whether or not your client base includes those who have experienced stroke.

Namaste, Michele

Hot from the Inside: How Hot Yoga Heats Up 100% of Your Body Down to the Cellular Level and Puts You at Risk of Heat Stroke

The American Council on Exercise (ACE), self-identified as the largest non-profit health and fitness certification, education, and training organization in the world, just published a scorching report on the effects of Bikram yoga on core body temperatures.  Bikram-franchised studios teach trademarked Bikram Yoga, a 26 posture sequence with two breathing exercises in a room heated to 105° with 40-50% humidity for 90 min. Copycat studios teach this same sequence under the taglines of hot yoga, hot hatha, or hot 26 and under similar conditions of heat and humidity for a duration of 60-90 minutes. I have experience with one studio that regularly allowed its temperature to creep up towards 110° and 60% humidity.

Is hot yoga safe??

The obvious question has always been “is it safe to practice yoga in such extreme heat  and humidity?” Now we have an answer.  The study found that 60 minutes into a 90 min class, nearly half of the study’s participants had core temperatures over 103°. Core temperature is that of your insides including your blood, guts, and other organs. Outside of the context of a hot yoga experience, adults at 103° or 104° are heading to urgent care centers and emergency rooms.

According to Bikram Yoga’s founder, Bikram Choudhury: [Parenthetical use is Choudhury’s not mine. MM]:

“The room is kept at this temperature or more for the following:

  • Keeping the body from overheating (contrary to popular misconception) 
  • Protecting the muscles to allow for deeper stretching
  • Detoxing the body (open pores to let toxins out)
  • Thinning the blood to clear the circulatory system
  • Increasing heart rate for better cardiovascular workout
  • Improving strength by putting muscle tissue in optimal state for reorganization
  • Reorganize the lipids (fat) in the muscular structure”

How do you actually keep from overheating?

A lesson on thermoregulation is warranted. When you exercise, you generate energy, which is released as heat. Excess core heat, a complex result of muscle activation, is transported from your core to your skin, where it is lost to the environment via several methods – radiation, conduction, convection, and evaporation.

Radiation. When your body is hotter than your surroundings, which it almost always is, then a greater quantity of heat radiates from your body than to it. In a thermal comfortable room, about 60% of heat loss occurs as radiant heat.

Conduction. The transfer of heat from your body to an object, say your mat in yoga. In a normally heated room, 3% of heat loss occurs due to conduction.

Convection. Heat transfer via moving gas/liquid, which is almost always occurring. In a reasonably temperatured room, 15% of heat loss occurs via convection.

Evaporation. Heat loss that occurs through ventilation/diffusion and sweating. This accounts for 25% of heat loss in a comfortable environment.

Metabolic heat is transported to the skin while activation of sweat glands causes sweat to be secreted onto skin surface, promoting heat loss by evaporation of the water portion of sweat, which does not contain toxins, by the way.

Body cooling by radiation and convection, which is about 75% of heat loss, depends on a significant difference between your core temperature and the air around you. When that air exceeds 98.6°, heat exchange is reversed and your body now gains heat by radiation and convection instead of losing it. Read that sentence again.

Now you are left with only one mechanism to cool your core temperature – evaporation of your sweat. Sweat can only cool you if it is allowed to evaporate. When the surrounding air is dry, sweat readily evaporates, cooling your skin. However, if the humidity is high as it is in hot yoga studios, evaporation is impeded, resulting in sweat accumulating on your skin and insufficient cooling of your body. You now have no way to lower your core temperature other than leaving the room. Ironically, ignorantly, and inexplicably, many hot yoga studios discourage you from leaving the room and instead suggest you lie down on your mat, where you are now at the mercy of gaining more body heat from conduction of heat from your mat to your body. Double jeopardy for studios with floor heating systems. You are now in a position of experiencing a critical heat load and developing the mother of all heat illness – heat stroke.

If you have not experienced a hot yoga class, I cannot impress upon you enough how much sweating happens. Many participants are soaked and dripping with sweat before the end of the first breathing exercise at the start of class. When sweating becomes your last resort to cool your core temperature, it must be matched by water intake or dehydration occurs.  Ironically, ignorantly, and inexplicably, many hot yoga studios discourage drinking outside one or two sanctioned water breaks.

When your core temperature reaches 104°, which happened to one of the study’s male participants (interestingly, male participants experienced significantly higher heat-induced heart rates and core temperatures), heat stroke becomes a real possibility. The Mayo Clinic defines heat stroke as “a condition caused by your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. This most serious form of heat injury, heatstroke can occur if your body temperature rises to 104 F (40 C) or higher.” Heatstroke can result in a number of complications including permanent damage to your brain and other vital organs and/or death. Heatstroke requires emergency treatment. Damage worsens the longer treatment is delayed, increasing your risk of serious complications or death.

What should hot yoga studios and teachers do?

I know enough hot yogis to also know it is futile to preach to them about the risks of the practice they love, so I offer, instead, best practices for minimizing that risk.

The ACE study made several recommendations for improving safety of hot yoga classes.

  • Shorten classes to 60 minutes. Study participants began experiencing dangerous core temperatures at the 60 minute mark
  • Lower the room temperature
  • Encourage students to stay hydrated by reminding them to drink water throughout the class
  • Stress to students that toweling off sweat undermines evaporative cooling in an already gravely compromised evaporation system

I would go bolder and say:

Hot yoga studios should reject the Bikram heat/humidity standard and implement a temperature cap of 98.6°, which would hopefully keep core temperatures below the 104° heat stroke threshold.  Humidity levels should also be lowered to allow for more efficient evaporative heat loss. I would hope to see further research that explores a range of lower temperatures and humidities as well include a greater number of participants, including novices and those unacclimatized, and an active control group.

New students should be offered a shortened, modified class to allow them to acclimatize. This study used regular practitioners of Bikram Yoga, who were acclimatized to 90 min at  105°/40%. However it takes up to 14 days to fully acclimate to these excessive conditions.

Hot yoga studios should provide ongoing training to its staff and students on how to recognize heat illness and what to do about it.

Namaste, Michele

bikram-yoga-safety-infographic