Shirshasana, commonly known as Headstand, is an inverted yoga posture debated for its health benefits and physical risks. As a position that fundamentally reverses the body’s orientation to gravity, it introduces unique physiological and biomechanical challenges. Understanding the posture requires separating established effects of inversion from speculative claims.
Physiological Effects of Inversion
When inverted, the normal hydrostatic pressure gradient is reversed, causing a transient shift of blood volume from the lower extremities toward the torso and head. This movement assists the return of venous blood from the legs back to the heart, essentially giving the cardiovascular system a short-term mechanical assist against gravity.
The change in blood pressure within the upper body is sensed by baroreceptors. These receptors trigger the baroreceptor reflex, the body’s rapid mechanism for regulating blood pressure in response to postural changes. Studies suggest that during a headstand, this reflex may lead to sympathetic nervous system activation, causing a decreased heart rate and increased vasomotor tone, which is a tightening of blood vessels in the periphery.
Inversions are also thought to aid the lymphatic system. By reversing gravity’s pull, the posture facilitates the drainage of interstitial fluid and lymph from the legs and feet toward the thoracic duct and upper body. Although some practitioners report a calming effect, studies measuring heart rate variability suggest that the posture may actually be associated with an increase in sympathetic activity, which is generally linked to the “fight or flight” response, rather than the parasympathetic “rest and digest” response.
Biomechanical Stress on the Cervical Spine
The cervical spine is built to support the weight of the head, but not the entire body. A supported headstand, even with proper technique, can place a significant vertical compressive load on the neck. Depending on the practitioner’s strength and form, the weight borne by the head and neck can range from 20 to 30 pounds, sometimes reaching 40-48% of an individual’s body weight, especially during entry and exit.
This excessive vertical compression increases the risk of microtrauma to the intervertebral discs and surrounding soft tissues. Insufficient core and shoulder strength forces the neck to absorb more of the load, potentially leading to misalignment, which can cause strain, nerve impingement, or disc injury over time. The neck is most vulnerable during the transition phases of entering or exiting the pose, particularly if the practitioner attempts to “kick up” or shifts their head for stabilization.
Beyond the direct spinal compression, the inverted posture causes a rapid and significant increase in intraocular pressure (IOP) within the eyes and, potentially, intracranial pressure. Studies have shown that a headstand can cause a twofold increase in IOP, which remains elevated for the duration of the pose. For healthy individuals, this pressure quickly returns to baseline upon exiting the pose, but the temporary spike poses a direct and serious risk for people with pre-existing eye conditions.
Identifying Absolute Contraindications and Safe Progression
Due to the significant physiological changes and mechanical stress involved, headstand is not appropriate for everyone. Absolute contraindications include any active neck injury, such as a disc herniation or whiplash, and conditions characterized by abnormal pressure or blood flow. Individuals with uncontrolled high blood pressure, certain heart conditions, or a history of stroke should strictly avoid inversions.
Conditions like glaucoma or a detached retina make the posture unsafe due to the immediate increase in intraocular pressure. Children under seven should not practice headstands because their cranial bones have not fully fused. Women are often advised to avoid the pose during menstruation, and anyone experiencing a severe headache or migraine should also refrain from the inversion.
Safe practice requires building foundational strength in the core, shoulders, and upper back before attempting to invert. Preparatory poses, such as Dolphin Pose or Plank, help condition the muscles necessary to distribute the body’s weight away from the head and neck. When first learning, it is essential to practice against a wall and under the guidance of a qualified instructor to ensure proper alignment and controlled entry, emphasizing a gradual lift rather than a forceful “kick-up”. The goal is to place minimal weight on the crown of the head, using the forearms as the primary base of support.