Vinyasa is a method of yoga in which movements form a flowing sequence in coordination with the breath. You can expect to move through a sequence of yoga postures linked together with specific transitional movements, including Sun Salutations. Each variation and transition is synchronized with the breath.

Absolutely. Vinyasa (or "Flow") classes are accessible to all levels. Pure Flow and Flow Yoga are great series to begin with. Hot Flow and Power Flow postures are intermediate, but the experience is more intense in a hot room. Power Flow introduces some variety into the postures, which is often challenging for new students. 

Hot Yoga LIte was designed to be a more moderate experience. it's a great place to start as the room is warm (not hot), but the postures are identical to our Hot Yoga class. Know that our teachers will help you modify the postures to fit your own experience and personal goals in any class.

Our Power Flow class is teacher-developed. The teacher designs their own class sequence each time they teach it. It gives our teachers an opportunity to express their creativity and you a chance to connect with your breath and movement while cultivating strong mental focus.

Pure Flow, Flow Yoga and Hot Flow are classes with a set sequence of postures. They will be the same every time. You don't have to think about what posture might be cued next, allowing you to focus on the alignment of a familiar set of postures. A set sequence also allows you to more easily see the progress you make in your practice.

Sun Salutations, down dogs, up dogs, warriors, planks and variations of pushups will form the core of these classes. However, the sequence in Power Flow does vary from teacher to teacher and day to day.

Each class is 60 minutes.

No, just yourself. If you're not a Sunstone member, please bring you own mat and towel, or you can rent them at the studio.

When bodies that were designed for movement are forced into cubicles and couches, weak, under-used muscles can feel pain. Yoga poses counters this by working virtually every muscle in the body through its full range of motion, using the body's own weight as resistance. At Sunstone, our yoga classes focus on creating a foundation of strength and proper alignment so that you can safely progress into a deeper practice and your full range of motion.

We recognize and celebrate every body's uniqueness, allowing postures to adapt to each student's anatomy and needs. Increased strength, flexibility, balance, endurance, mobility, range of motion, calorie burning, cardiovascular health, and pain relief are just a few of the changes you'll see in your body. In addition to the tremendous physical benefits, yoga hones your focus and concentration, relieves stress, and promotes better sleep, relaxation, and increased body awareness. (A consistent yoga practice is life-changing, but don't take our word for it - check out the Testimonials page!)

At our studios you can experience yoga  in a heated room with either our Hot Yoga class or Hot Flow, Hatha Yoga in Hot Yoga Lite or Yoga Calm, Vinyasa Flow with Flow Yoga, Power Yoga or Calm Flow and don't miss Yoga Core our resistance stretching class. Hot Yoga Lite is a great beginner's yoga class!

Our signature Hot Yoga class (previously called the Fire Series) is done in a controlled environment that keeps the room at body temperature (98.6°). This provides a unique and superior experience to both Bikram yoga and Core Power Yoga. To read more about our environment read the Heat, Humidity & You section below.

by Brandon Hartsell, Sunstone Co-Founder and current Yoga Alliance chair.

For those of us who have an existing yoga practice, whether yoga works rarely enters our mind, because the fact that yoga works is a matter of experience. Yet, it is a worthwhile question both for practitioners and those steeped in traditional forms of exercise or considering a yoga practice. Yoga works on the body, mind and emotions in positive, life-changing ways. Many people will enter a yoga room with the goal of becoming slimmer, or changing their physical abilities in some manner, and months later find they are not only physically changed, but their lives have changed. These life changes will have occurred solely through practicing yoga postures.

Starting with weight loss, let’s look at why yoga works successfully as a path to fitness.

Muscles metabolize calories when they are stimulated. One pound of muscle metabolizes 35 – 50 calories every 24 hours. However, the more muscle used, the greater the stimulation, and in turn the more calories required. In running, you use approximately 25% of the body’s muscles. That 25% is only put through about 15% of its range of motion. That is: 15% X 25% = 3.75% of the body’s muscle cells being stimulated by running. Calories are burned because of the duration and repetition of that exercise.

In contrast, a typical yoga practice uses the muscle’s full range of motion, and the muscle is almost completely stimulated. With practice, a yogi or yogini is contracting, stretching and putting resistance on a large percentage of the body’s muscles, through nearly 100% of their range of motion. Therefore, the typical yoga practice is a more efficient use of muscle tissue and higher caloric expenditure results.

Intense forms of yoga, such as hot yoga, work to stimulate the cardiovascular system in the same way. The more muscle cells involved in the activity, the more oxygen required, and in turn the greater the effectiveness of the exercise. In general, oxygen consumption over time depends on 4 things:

1. Muscle mass involved in the exercise;
2. Percentage of muscle cells involved in the exercise, or the range of motion the muscle mass is put through;
3. The number of times the muscle must make the movement;
4. The resistance on the muscles during the movement.

Increase any one of these elements, and the time required to get the same cardiovascular result is decreased.

Continuing with the example of running, if you run up a hill you get very out of breath. Running uphill forces the legs through a greater range of motion with more resistance, and the oxygen requirements skyrocket, meaning less time is required to get the same cardiovascular result as running on a flat surface. In a yoga practice, however, applying resistance to a high percentage of muscle mass through a high range of motion, you don’t need to keep your heart rate up for prolonged periods of time, because you use more oxygen in that time.

After exercise, the body continues to consume greater amounts of oxygen than before the exercise. This is called “excess post exercise oxygen consumption” (EPOC). It simply means your body is still working harder after you stop exercising, while it restores itself to its normal resting state. The duration of EPOC is proportional to the number of muscle cells used and the intensity of the exercise. Because of the high amount of stimulated muscle in yoga, the EPOC is high. Some styles of yoga, such as hot yoga, have an even greater EPOC, because of the increased heat and humidity of the yoga environment.

Beyond its effectiveness at calorie burning and cardiovascular exercise, the balance of strength, flexibility and concentration should not be overlooked in a yoga practice. Many athletes in high impact activities with high risk of injury must use strength and flexibility training as a separate component of practice to enhance their ability in their chosen sport, or to protect themselves from the effects of repetitive stress on the body. Running continues to provide an excellent example, because of the high impact of constant weight bearing on knee and ankle joints. While running is effective for cardiovascular development and leg strength, some runners find they get limited upper body strength and a decrease in flexibility. In time, this can lead to injury or discomfort.

Yoga is one of few exercise practices that builds strength and flexibility to the whole body with minimal risk of injury or long-term physical damage. By moving in and out of the postures in a controlled manner and holding the pose over time, the yogi or yogini uses his or her own body weight as resistance. A recent study at the University of California at Davis found that 90 minutes of yoga practice 4 times a week over 8 weeks increased muscular strength up to 31%, muscular endurance up to 57%, and flexibility up to 188% in a group of healthy but previously sedentary college students. Proper practice of yoga works every part of your body equally, and doesn’t overwork the muscles, leading to better balance and alignment in the body and less chance of injury than other forms of traditional exercise. If the goal of exercise is increased physical benefits, the low impact, low risk aspects of a regular yoga practice inevitably mean the yoga practitioner can be confident his or her practice will continue to be regular.

Beyond its purely physical benefits, yoga increases your body awareness and helps decrease stress. The increase in awareness leads to better decisions about what to eat. If you have a regular yoga practice, you are less likely to eat something that is going to make your practice uncomfortable. Instead of fueling your body with lots of foods that digest slowly, the body begins to ask for lighter foods higher in nutrients. It is more comfortable to do yoga with less food in your system.

Also, by reducing stress, yoga reduces eating as a stress response. Comfort foods work, but they usually add unneeded or unwanted calories. Our stressful lives contribute to weight gain because stress increases the hormone cortisol. Cortisol stimulates eating, and encourages calories to be converted to fat. By decreasing stress, we decrease the amount of cortisol our bodies produce.

As awareness increases and stress decreases, yogis also understand that the latent energies of the body are released through the practice of asana. Right energy used begets more energy. As the body opens, aligns, and breath comes under control, we get the synergistic effects of yoga. In traditional forms of exercise like running or cycling, the beginner athlete will initially improve his or her performance by keeping the mind off what they are doing; in effect, distracting themselves from the hard work. But top athletes must be aware of and completely focused on every movement. In this way, they can perfect their breath and movement to conserve energy. But there is a monstrous gap between the two and bridging that gap takes tremendous training. By its very nature yoga requires awareness and attention to the smaller details from the very beginning. Your skill in yoga grows proportionally with this improved awareness. So achieving balance between strength, flexibility, and concentration is a self-mastery with unlimited benefits to the body and overall health of the practitioner.

Increased awareness is both cause and effect of the increased health benefits of a regular yoga practice. You may enter a yoga class for the physical benefits, and within a short time, find that you have received much more.

-- Brandon Hartsell, CEO & Co-Founder

Yoga Core Class

The primary tool we have to strengthen and stabilize your core muscles is regular practice of isometric, passive, dynamic, and active stretching exercises. Yoga Core is offered in 30 and 60 minute classes in a strong dynamic sequence. You will see elements of the Yoga Core class, and specific postures using our Pain Free Yoga technique, in the regular Hot Yoga series.

Take Pain Out of Your Yoga Practice

Do you experience pain in your yoga practice? Based on informal research and practical experience, about 60% of readers are reluctantly nodding their heads. If you’ve had a regular yoga practice for 5 or 6 years, the odds of pain are even higher, and you may not even want to risk nodding your head. Following years of dedicated practice, too many yogis are experiencing pain that stretching does not fix.

And yet we know that yoga heals pain. People walk into their first class with chronic, even debilitating, pain, and walk out feeling better then they have in years. New practitioners learn to breathe deeply, to relax more completely, to balance and strengthen their bodies, and to push to the edges of their flexibility to find release and bliss. It can work for a long while; but too often, yogis are pushing through pain to get deeper, without resolving why the pain is there, or creating new injuries by stretching into ranges they can’t control.

Elizabeth Rondeau got relief from the chronic neck pain she suffered after only two yoga classes, and was instantly hooked. Five years later, the yoga instructor and studio owner started to develop pain in her low back. “It was weakness and degeneration,” says Rondeau, and kept practicing through it. The pain kept up and suddenly there were postures in her regular practice that had to be avoided. Standing Forehead to Knee was the first to go, then Balancing Stick. Triangle pose followed a short time later, and suddenly, sit-ups were starting to hurt. Her chiropractor was no longer able to help her out of pain. “I was discouraged,” Rondeau says, “and more than a little concerned, wondering what I was going to do about it.”

Pain does not have to be part of your yoga practice.

The current model of yoga practice in this country offer practitioners like Elizabeth a few choices: push through the pain, adapt your posture to compensate around the pain, or avoid certain postures or yoga styles altogether.

Tricia Keller pushed through pain with the encouragement of her yoga master. Pain was simply a part of her yoga practice. But pain is an indicator that something is wrong, and often, the cause of the pain is not muscle tightness or inhibition, but muscle weakness. You are not listening to your body if you are attempting to work through pain with yoga; there is a better way to get there.

Here at Sunstone, students and instructors like Elizabeth and Tricia are finding relief by addressing weakness in the body with isometric and active stretching techniques. Pioneering a methodology we call Pain Free Yoga™, Derrek Taber and Brandon Hartsell developed a series of muscle tests, correction poses and core strengthening yoga classes to turn on weak or dormant muscles by focusing on active symmetry and increasing strength in the extreme ranges of motion.

All styles of yoga can do a great job of strengthening, but the focus is generally on maximizing flexibility, which we believe has its limits. The body simply wasn’t designed for unlimited passive stretching without proportional strength in the passive range, and pain is often a sign of weakness. If you hurt going into Downward Facing Dog, the problem may not be lack of flexibility in the spine and hamstrings, but lack of stabilization in the hips and abdominals.

When a muscle is in a range it can’t control, reciprocating muscles move in to compensate, potentially leading to pain and tightness from overuse or incorrect use. The reciprocal muscles tighten to protect the stability of the weak muscle, and all the stretching in the world will not loosen a muscle that is being told by the body to tighten. The muscle is tight because it needs to be tight, so the problem is not the lack of flexibility in the stretching muscle but weakness in the muscles that support the stretch.

The answer is to address the strength in the weak area to alleviate the pain, and allow the flexibility in the opposing muscles to follow.

What happens when we stretch

The muscles contain mechanoreceptors, called Golgi tendon organs & muscle spindles, which inform the central nervous system of activity in the muscle and cause the muscles to contract or relax. When you stretch a muscle, the central nervous system signals the muscle spindles to resist the stretch, and the muscle reflexively contracts. That’s what it is designed to do, to prevent you from moving into a dangerous, unstable position.

If the stretch continues beyond 6 seconds, however, the Golgi tendon organ responds, causing a relaxation, or shutting down, of the muscle. This is a protective reflex mechanism that allows the muscle to relax before reaching the end of its elastic range, which can damage the muscle fibers. Under normal conditions, the muscle shuts down only temporarily; within a few moments, it turns back on. But over time, repeated passive stretching with no attention to proportional active stretching trains the muscles to stay shut down.

Like a car battery that needs a jump start,” explains Derrek, “isometric contractions charge up the dormant muscles, and by adding strength in the extreme ranges through repeated practice, the muscle maintains its charge and gradually increases its power.”

In addition, reciprocal inhibition means that as a muscle contracts, its opposing muscle automatically releases and stretches. So the stronger and more stable we can make the hips in Downward Facing Dog, the more likely the spine and hamstring flexibility will increase without pain.

Recent research, although small in scale, challenges the common perception in yoga that all stretching is good. An Australian study of 1538 Army recruits found no statistical difference in injury reductions between groups of recruits who added stretching exercises to their regular jogging and side-stepping exercises.¹ A study of marathon runners in Hawaii found that people who stretched after their run had a lower chance of injury than people who stretched before running, and the stretching group in fact had a 33% higher chance of injury over those who did no stretching at all.² One study of athletes with groin injuries found that 23 of 34 injured athletes who only strengthened and did not stretch returned to pre-injury levels within 3 months, compared to only 4 of 34 athletes in the stretching group. Even more interesting, the study concluded that the athletes who had not stretched nonetheless had the same increase in range of motion as the stretching group.³

Add active stretching techniques to balance passive stretching

When you lift your knee up toward your chest for Wind Relieving pose, the muscles of the lower abs are working. The height you can lift it up is your active range of motion. As soon as you grab the knee with your hands and pull it closer to your chest, you’ve moved into the passive range, the area you don’t control. The difference between the active and passive range is therefore unstable. Injury is more likely to occur in this uncontrolled range. By increasing the active range of motion through exercises that strengthen the body into its extreme ranges, the gap decreases.

The goal of Pain Free Yoga is to increase the active range of motion to within a close percentage of the passive range, and then move each of them forward together. The concept isn’t really new. The exceptional fitness yogis we have known who have really excelled have always used active stretching. Early in the development of their yoga practice, their bodies allowed them to go into the extremes of a position, and the next logical step was to contract their muscles. In Separate Leg Stretching, for example, an exceptional yogi will instinctively activate the muscles by lifting the heel off the ground, or releasing the foot in Standing Head to Knee.

"These are active postures that were never taught as active stretching," Hartsell concludes, “but they are present in people with exceptional practices.” Pain Free Yoga emphasizes and encourages a more exceptional yogic practice by addressing weakness directly before moving into depth. Waiting until you are passively flexible enough to “do” a posture before considering your active flexibility will only work if you are predisposed to get to that point before the muscle is conditioned to shut down.

Advance Symmetrically

Correct progress is symmetrical progress. Pain Free Yoga techniques are meant to be used with traditional yogic techniques to fortify and complement other styles, allowing you to achieve the increased range of motion you want from a position of strength, stability and balance.

The first step to identifying where weakness exists is to look for symmetry in a few basic postures. Do both legs extend or flex to the same degree? Do you twist as deeply on both sides of the body? Can you lift both arms to an equal height?

“The PFY method addresses what you can’t do, not what you can do, because it is what you can’t do that ultimately causes you problems,” Taber says. “If you only stick with the postures that don’t cause you pain, then you haven’t taken care of the pain; you’ve accommodated for it. It’s what you can’t do that is going to get you in the end.”

Pain Free Yoga’s philosophy is to address the weak postures first. Lack of symmetry or imbalance in postures indicates weakness or inhibition. Addressing the weakness by strengthening into those postures in the extreme ranges - regardless of existing limitations – brings both sides into a symmetrical state, and then both sides can move forward together.

Unbalanced flexibility, like abnormally large ranges of motion in some movements and less in other movements in the same joint may contribute to injuries. In classical ballet, for example, where dancers have extraordinary range of external rotation and abduction of the hip combined with less than normal range of internal rotation and adduction, 30% of dancers complain of lateral knee pain, and 33% suffer from anterior hip pain.⁴

Stability, Mobility, Strength Endurance, and Balance

Stability, mobility, strength endurance and balance are the key components of our technique, and balance is the culmination of all components. Balance involves the integration of muscular forces with biochemical information and neurological sensory information from the joint and muscle. This integration positions the body’s center of gravity within the base of support.

Even when a person appears to be motionless, the body is undergoing constant postural sway, caused by reflexive muscle contractions that correct and maintain the posture. When balance is disrupted, the response to correct is primarily reflexive and automatic. This is why cueing does not always work. If there is muscle inhibition, cueing the person may only cause further compensatory patterns, by over-strengthening the strong muscles while the inhibited muscles remain unresponsive.

Understanding Yoga in a New Light

So what about the other styles of yoga? According to Hartsell and Taber, some yoga techniques are reactions to long-term neglect of the active range of motion. “It’s easy to understand how some of these styles evolved,” says Hartsell. “The instructor develops pain and assumes that he or she was doing something wrong: his or her alignment was off, or they should not have performed a certain posture that now hurts.” From there, they develop a means to compensate for the new pain with the false assumption that a lack of pain in their new technique means it is the correct technique, and will also work to help their students avoid injury. Hartsell and Taber believe it isn’t what they were doing that caused them pain – but what they weren’t doing. “Lack of strength is the issue, not the activity,” Hartsell says. Often ‘yin’ is championed as the solution to ‘yang’ injury. But athletic ‘yang’ yoga is no more risky than gentle ‘yin’ forms of yoga. A gentle approach may help you compensate around an injury, but it is not a solution if the injury or pain is caused by a lack of stability and strength.

The prescription for Elizabeth and Tricia: some muscle testing and stimulation, and a regular regimen of core strengthening classes that focus on active and isometric stretching.

For Elizabeth, Tricia, and hundreds of other Dallas yoga students, Pain Free Yoga is the next big thing to get hooked on: “Yesterday I had the best, strongest practice that I’ve had in the last 7 months and after only 2 visits!” Elizabeth says. “Except for Standing Head to Knee I didn’t have any pain in anything. I am so excited, I already KNOW how awesome Pain Free Yoga is going to be for my students.”

That’s what Pain Free Yoga is about. Avoidance and compensation don’t resolve the problem, symmetry and active range of motion do. “You can have your yoga practice back,” concludes Hartsell. Pain Free Yoga is about balance and a strong foundation, core principles of all yoga disciplines. “As long as you are not in pain,” Hartsell says, “keep doing what you’re doing. Just don’t assume that pain has to be part of it.”

The basic rules of Pain Free Yoga^™

• Pain is a sign of weakness. Never stretch into a painful posture; first fix the weakness, then stretch.
• Any stretch, even a passive one, can be activated. Always strengthen into poses. Think strengthen, not stretch.
• Achieve active symmetry through all ranges of motion. Work to your limited side, allow it to catch up. Remember it is what you can’t do that will hurt you in the end.
• The key components of Pain Free Yoga in all postures are stability, mobility, strength endurance, and balance. All of these need to be combined to have the best possible yoga practice.

Components of Pain Free Yoga^™

• Stability - the ability to control all movement in the body under all conditions.
• Mobility - the joint's ROM, regardless of muscular control.
• Strength Endurance - the ability to maintain a set amount of force productions in a muscle over a period of time.
• Balance - the culmination of all components. Balance involves the integration of muscular forces with neurological sensory information from the joint and muscle, and biochemical information. This integration positions the body's center of gravity within the base of support.

Pain Free Yoga™ for back pain

Try these postures at home for a few minutes every day, or do a few sets of each right before or after your regular yoga practice.

Lying on your back, bend your right knee and place the foot on the outside of your left knee. Keep both shoulders on the ground, and without lifting or shifting the hips, simply roll over onto your left hip as far as you comfortably can. Placing a brick, or your fist, underneath the right knee to create a small amount of resistance, and then gently push your knee into your hand. Hold each time for 6 – 8 seconds, and with a 2 – 3 second release in between, repeat activating the muscle in this very light way – 20% effort is enough – for 6 to 8 repetitions.

Tip
Look for symmetry. Do you twist deeper on one side? Practice Strong Floor Spine Twist on your limited side for a few days, and then test both sides again. When both sides are in balance, then practice on both sides.

Muscles Working
One side TVA, opposite side external oblique; also internal oblique, pectinius, adductor brevis

Strong Dog

Begin on your hands and knees in 4 point position, with knees directly under the hips and hands directly under the shoulders. Press up onto your toes in an easy Downward Facing Dog, and then apply 20% effort to pull your feet and hands toward each other. Imagine you are closing your body up like a jackknife, but your hands and feet would have to arc under the floor to get you there. Don’t push too hard here. You should feel only a light activation in the lower abdominals. Hold each time for 6 – 8 seconds, and with a 2 – 3 second release in between, repeat the posture 6 – 8 times.

Tip
Try these adaptations to Strong Dog: Bring the heels of the feet together. Continue to pull the feet forward and the hands back. Walk the feet in 6 inches, pull the feet and hands together. Keep walking the feet closer until your hands and feet are almost together, if you can.

Remember to back away from pain. Improve gradually. Lift the right leg up in the air, pull the left foot and hand together. Repeat on the opposite side.

Muscles Working
rectus femoris, iliacus, psoas major & minor, external oblique, pyramidalis, internal oblique, rectus abdominis

Strong Half Moon Angel

Lying on your back, walk your legs over to the right side of your mat, as far as they comfortably go. Pull your upper body gently to the right also, if there is no pain, so that you have a half moon shape along the left side of the body. Keep both feet and your face pointing up toward the ceiling. Place the back of your right hand on the outside thigh, or place a block between the hand and thigh, and gently try to fold your upper and lower body together. Both legs and the upper body pull to the right, into the resistance of the hand and arm. Hold the pressure at 20% for 6 – 8 seconds and back off for 2 seconds, then repeat 6 – 8 times.

Tip
Turn the outside foot outward to externally rotate the right leg, and repeat the posture. Turn the outside foot inward to internally rotate the left leg, and repeat the posture.

Muscles Working
erector spinae – Longissimus, iliocostalis, spinalis, Semispinalis, multifidus, external and internal oblique, TVA, latissimus dorsi, quadratus lumborum

Strong Pigeon

Begin on your hands and knees in 4 point position, with knees directly under the hips and hands directly under the shoulders. Pull the right knee forward and bring your right foot to the outside of the left knee. Drop the knee down close to the left wrist. Apply gentle 20% pressure to push the knee closer to the wrist. The left knee and shin are pressing gently down and back, and you can lightly activate the glutes to tuck the tailbone under. Hold each time for 6 – 8 seconds, and with a 2 – 3 second release in between, repeat the posture 6 – 8 times on each side.

Tip
To increase the active stretching in this posture, try to lift the right leg up toward the left armpit, pulling up from the foot to work deeper into the external rotation at the hip.

Muscles Working
Psoas minor, lower abdominals

--Brandon Hartsell CEO & Co-Founder

1. "Injuries in Australian Army Recruits, Part III: The Accuracy of a Pretraining Orthopedic Screen in Predicting Ultimate Injury Outcome," Military Medicine, Vol. 162, pp. 481-483, 1997
2. "Rates and Risks for Running and Exercise Injuries: Studies in Three Populations," Research Quarterly for Exercise and Sport, Vol. 58, pp. 221-228, 1987
3. “Muscle strain injuries: clinical and basic aspects” Med Sci Sports Exercise 1990;22:436–43.
4. “Stretching Scientifically, A Guide to Flexibility Training,” Thomas Kurz, 2003; pp.10

Deep in our brain the hypothalamus houses our body's thermostat and monitors our core temperature. When we are exposed to heat and our core temperature begins to rise above 98.6 degrees our cooling mechanism is triggered. Our heart is triggered to pump more blood from our body core to our skin, our sweat glands are triggered to bring moisture to the skin's surface, and as our sweat evaporates into the air it pulls heat from the skin and blood. This cooler blood circulates back to cool our core.For this cooling mechanism to be effective there has to be air moving across our skin into which the sweat can evaporate. The more air moving across our skin the easier it is for our sweat to evaporate. Likewise, the dryer the air the easier it is for our sweat to evaporate. This is why a breeze is cool and a dry day feels cooler than a humid day. In summary our body's ability to cool itself is affected by three things: 1) temperature, 2) humidity and 3) air movement.These three things also determine how hot it feels to us. Our body is able to sense even small differences in temperature changes but is extremely efficient at maintaining our core temperature. As Texas Tech physiology professor Thomas Pressley, PhD points out, "Despite the extremes of temperature that you might expose yourself to, your body temperature never varies more than a couple of degrees. Going from your air-conditioned office to a hot parking lot to your air-conditioned car, your body temperature probably won't vary enough to measure." Even though the impact on our body of going from one temperature to the next has minimal impact on our core temperature we are very sensitive to the change.

The temperature we feel is a function of heat, humidity and air movement. The function commonly used to measure felt temperature is heat index. The heat index formula assumes a steady air movement of 5.8 mph and then combines variable heat and humidity to calculate the temperature our body feels. The Sunstone Hot Yoga & Hot Flow Series class targets a temperature around 98.6 degrees and a humidity of around 60%. This is a heat index or felt temperature of 124.6 degrees. Because our body is able to sense even small difference in temperature changes, large changes can be startling. When we first walk into a Hot Yoga or Hot Flow class there is little doubt that it is hot. Our bodies immediately begin to cool themselves and we adjust to the temperature. Conversely, when we leave a "Hot" class the lobby feels substantially colder than before class. The lobby has not gotten colder but it feels that way because we have adjusted to a higher temperature and also because we have sweat on our skin. Even during class small changes in the heat and humidity can make the room feel hotter or colder. These small changes will have no impact on our core temperature and very little impact beyond our skin surface, but they are likely to be felt. For example if the temperature rises 1 degree to 99.6 and the humidity rises 1 degree to 61% this represents a heat index of 129.3 which is a 4.7 degree felt temperature changeⁱ.

Until our body is acclimated heat exposure creates stressⁱⁱ. Our body's ability to function in the heat is not a measure of our physical condition rather of our heat conditioning. Being in good condition will help but only exposure to heat will allow our body to adjust. The following elements improve with exposure:

• Core temperature
• Sweat rate
• Blood lactate
• Blood and urine osmolality
• Rating of perceived exertion
• Skin temperature
• Heart rate
• Plasma volume changes
• Hydration status
• Index of thermal strain

Full acclimatization takes as long as 14 days but most of us will feel more comfortable after only a few consistent classes. This chart shows the number of days acclimation takes for certain elementsⁱⁱⁱ

1. Our blood volume pumped to the skin increases
2. We start sweating at a lower body temperature
3. Our hormones adjust so we sweat more water and less salt

Because of salt (electrolyte) loss prior to acclimatization (number 3 above) it is essential that we take electrolyte replacements. This is also true when we increase exposure by taking more classes.

It is absolutely critical that our bodies be given enough water to remain hydrated. Hydration must occur prior to heat exposure and/or exercise. Our body can absorb one-quarter liter per 10 – 15 minutes. For most of us water loss due to sweating is greater than one-quarter liter per 10 – 15 minutes.A dehydration of only 2% body weight has been shown to reduce performance by as much as 10%^iv.We should try to avoid dehydration by consuming 2/3 ounce of water per pound of body weight each day. This is any addition to any water we sweat out during class which will be as high as 3 liters per hour^v. During class we should avoid wiping sweat from our body. The removal of sweat does not help remove excess heat but instead stimulates additional sweating and therefore additional water loss.

--Brandon Hartsell
CEO & Co-Founder

1. The task of controlling the felt temperature of a hot room is not trivial. Most of our studios have automated systems that are constantly working to maintain a stable heat index. These systems monitor heat and humidity and based on the measurements adjust the furnace and humidifier in real time. Of course heat and humidity are always escaping the room so as the furnace and the humidifier adjust, there can be ±8° swings from desired heat index. Compounding the felt temperature issue is that the amount of humidity impacts the density of the air and less dense air decreases air flow. A ceiling fan or furnace blower spinning at a constant rate will push more air the greater the air density. Unfortunately for felt temperature as humidity decreases density increases. So as the humidity goes down the fans are more effective. And as we learned the more air moving across our skin the easier it is for our sweat to evaporate and cool us. So a room cooling via a reduction in humidity will feel extra cool because of increased air flow which improves our bodies cooling ability.
2. Signs of heat stress can be muscle spasms, heavy sweating, fatigue, pale and clammy skin, weakness, nausea, dizziness, and a red face.
3. Days of practice should be done in fairly close succession to allow for acclimation.
4. Medically, dehydration can be classified into three levels:
• Mild: dry mucous membranes (lips and mouth), normal pulse, darkened urine, mild thirst.
• Moderate: very dry mucous membranes, rapid and weak pulse, darker urine, thirst.
• Severe: very, very dry mucous membranes, an altered level of consciousness (drowsy, lethargic, disoriented, irritable), no urine, no tears, and shock (indicated by rapid and weak pulse, rapid breathing, and pale skin).
5. Research clearly shows that relying on thirst will cause us to underestimate fluid needs.