Looking at the biomechanics of this inversion can teach us how to mitigate injury.
Often referred to as the King of yoga postures, Sirsasana I (Headstand) can be a refreshing and energizing inversion that, when practiced consistently, builds strength in the upper body and core. For years, the posture has been praised for providing physical benefits— but it’s also been criticized for exposing the head and neck to weight that could cause injury. In fact, in some yoga communities, Headstand has completely lost its place at the throne, and it has even been banned in some studios.
By Jules Mitchell
In traditional yoga practices, Headstand is an inverted posture taught in seven different forms. In the variation we’ll look at here, the base of support is the top of the skull. To get into the pose, come to your knees, place your forearms on the floor, and clasp your hands, positioning your elbows shoulder-width apart (creating an inverted V from clasped hands to your elbows). Find the floor with the crown of your head, and cradle the back of your head with your clasped hands. Engage your upper body as you press your elbows and wrists into the floor, and lift your shoulders. Once you establish this stable base, lift your legs off the floor until your body is inverted and erect, balancing on your head and forearms.
These are standard cues for teaching Headstand. Where things get inconsistent, however, is when it comes to the cues that help students figure out how to distribute their weight between the head and the forearms. Some say there should be little to no weight on the head, whereas others apply an iteration of the Pareto principle (i.e. the 80/20 rule) and recommend more weight on the forearms than the head.
Insightful teachers understand an “ideal” distribution cannot be taught, as it will depend somewhat on individual anthropometrics (the science of measuring the size and proportions of the human body). For example, if the length of a practitioner’s upper arm bones is longer than the length of her head and neck, that yogi’s head may never reach the floor; if the practitioner’s head-and-neck length are longer than her upper arm bones, she may struggle to reach the floor with her forearms. These examples are extremes, but they do serve to explain why we can’t cue an individual into proper weight distribution, as the proportions between the top of the head and the forearms depend on an individual’s specific anatomy.
In hopes of providing data for better understanding how safe (or unsafe) Headstand might be, researchers at the University of Texas at Austin studied 45 experienced, adult yoga practitioners who were skilled enough to hold the pose for five steady breaths. The study resulted in a 2014 paper published in the Journal of Bodywork & Movement Therapies that helps shed some light on the ongoing Headstand debate.
What the scientists looked at
In a lab, 45 experienced yogis completed a 10-minute warm-up. Then, reflective markers were attached to their chins; foreheads; earlobes; cervical (C3 and C7), thoracic (T9), and lumbar vertebrae (L5); femurs; and toes. This allowed the researchers to measure the practitioners’ movements with a motion-capture camera system. Force plates (think high-tech bathroom scales that measure how much force is being generated by the bodies they come in contact with) were used to measure how much force acted on their heads and necks throughout the exercise.
The yogis were then split into three groups based on how they typically enter and exit the pose. (There were 15 yogis studied in each group: 13 women and two men.) They were asked to enter the pose, hold the full inversion for five breaths, and then exit the pose. Data were collected during these three distinct phases of each variation—entry, stability, and exit:
• Split-leg entry and exit: Knees bend and pull into the chest; one leg straightens and the other follows until both legs are stacked above the hips and shoulders. Reverse to exit.
• Curl-up and curl-down entry and exit: Knees bend and pull into the chest; both knees straighten simultaneously until both legs are stacked above the hips and shoulders. Reverse to exit.
• Pike-up and pike-down entry and exit: Straight legs lift together until ankles, knees, hips and shoulders are stacked. Reverse to exit.
What’s your version of Headstand?
Do you come into and out of Sirsasana I (Headstand) by curling up, with one leg followed by the other, or with your legs together, piking up and down? Turns out, how you transition in and out of Headstand makes a difference when it comes to how much force is placed on your head and neck. Here are the three variations of this inversion the scientists studied.
What the study found
This research assessed force, neck angle, loading rate, and center of pressure:
Force: Among all 45 study participants, the maximum force applied to the crown of the head during entry, exit, and stability in all three variations of entry and exit was between 40 and 48 percent of participants’ body weight. For a woman weighing 150 pounds, that equals somewhere between 60 and 72 pounds. The threshold for neck failures is unclear; the authors cited an estimate ranging from 67 and 3,821 pounds, noting that men tend to have a greater threshold for weightbearing on their necks. This suggests women should be especially cautious when practicing Headstand.
The stability phase, where practitioners held Headstand for five breaths, exhibited the greatest force on the head. Exiting the pose contributed the least force on the head. It is important to note that anthropometric data were not collected.
Loading rate: To understand loading rate, it’s crucial to understand “strain rate.” Strain refers to the change in shape of the tissue when a load is applied, and rate refers to the speed at which a load is applied. In the human body, resistance associated with faster loading rates can lead to increased load failure. With this in mind, it is important to appreciate the benefits of entering Headstand slowly. The study found that loading rate was fastest as the yogis entered Headstand (no matter which version of entry), followed closely by coming out of the pose (again, no matter which version of exiting). The group of yogis piking into the pose had slower loading rates than those kicking up, suggesting that piking up into Headstand may be best for reducing the loading rate
Neck angle: Loading the neck during flexion has long been thought to increase risk for injury; therefore, neck angle was examined across all techniques. The data showed the neck angle during the peak force was not significantly different across phases or technique. Overall, the neck was in extension during entry, and in neutral or flexion during stability and exit across all techniques. The bottom line: There is potential for loaded neck flexion when practicing Headstand, which may deter you from including this posture in your practice.
Center of pressure: The center of pressure at the crown of the head was measured to determine how much shifting takes place during the three phases of Headstand. Regardless of technique, all the practitioners’ center of pressure shifted around their heads somewhat, mostly as they entered and exited the pose. This ability to shift and adjust during the pose might be beneficial by reducing the maximum force applied to the crown of the head (because ground reaction force decreases as the body veers off its vertical axis). But swaying side to side in Headstand may expose the neck to lateral (side) force, which may cause injury.
What the results teach us
So, is Headstand safe? While this research doesn’t give us definitive answers, it is the first study to quantify loads on the neck during Headstand and can help us move forward in the safety debate. Keep in mind, however, that other versions of Headstand (like Tripod Headstand) were not examined, and we don’t have data on beginners.
I believe it’s most likely that a certain amount of weight on the neck and head is safe when met with a slow, controlled entry technique. On the flip side, an uncontrolled or high-momentum kick-up and kick-down could put the neck and supporting structures at risk for strains, fractures, and neurological complications.
For optimal safety, I’d recommend practicing the most difficult entry and exit: the pike-up and pike-down, which was shown to impose the least amount of force on the crown of the head, as well as the lowest weight-loading rates.
How I teach Headstand
Long ago, I stopped teaching Sirsasana I in public yoga classes because of the uncertainty around its safety. I do, however, practice the pose regularly in my own practice and teach it in my yoga teacher trainings. This study validated my safety concerns and further emphasized the importance of developing skill over achieving the aesthetics of the pose. Here are the steps and tips that may help keep you safe when practicing this pose:
• When appropriate, accommodate your anatomy by using a blanket to add height to either your arms or your head and neck.
• Press the lengths of your inner and outer forearms into the mat, while trying to lift them off the mat (they won’t actually go anywhere). This co-contraction helps to build strength in the shoulder complex.
• Build this co-contraction endurance for a minimum of eight breaths before attempting to lift your feet off the floor. (Eight breaths should account for entering, holding for five breaths, and exiting the pose).
• Repeat the above endurance exercise with your feet elevated on a block, then a chair, working the pelvis over the shoulders.
• Gradually and progressively learn to pike up into the pose.
• Avoid the pose when your stress levels are high, sleep is compromised, you are fatigued, other psychosocial factors are affecting your well-being, or you have a contraindicated medical condition.
Author Jules Mitchell MS, CMT, RYT is a yoga teacher, educator, and massage therapist in San Francisco. She contributes to yoga teacher training programs and leads workshops worldwide. Her upcoming book, Yoga Biomechanics: Stretching Redefined, published in 2018. Learn more at julesmitchell.com.
Model Robyn Capobianco, PhD, is a biomechanics expert and researcher. Learn more at drrobyncapo.com.
This article was first published in the print edition of Yoga Journal Singapore, which is now Yogahood Online.
