Over the past few years leg-crossing has seen an improvement in its reputation, due mostly to a rash of articles and blogs touting the changing medical opinions concerning this position. Sitting cross-legged has been blamed for a lot of things over the years – high blood pressure, varicose veins, nerve damage – and posts like the one found at www.sciencealert.com.au seem to take the fact that these associations were exaggerated to indicate that crossing your legs is a harmless way to sit.
While the position may not lead to the types of hazardous or unsightly conditions named above, it can lead to lower back pain. This is important to remember in a society where 8% of the population is estimated to have chronic back pain and back pain is one of the leading causes of work disability. Crossing your legs may not damage nerves as once suspected, but it can damage your lower back muscles and joints if done on a regular basis, and this latter fact is nothing to sneeze at.
The two back pain causes discussed here – abdominal deactivation and sacroiliac joint dysfunction – were noted in a study that sought to assess how sitting cross-legged affects core muscles. The researchers acknowledged the result of previous studies, namely, that crossing of the legs deactivates the internal abdominal oblique. This muscle stretches from the front of the hip bone to the bottom of the rib cage in the back on each side of the body. They work with another pair of deep abdominal muscles – the transverse abdominus – to support the spine and maintain proper posture as the torso rotates to the side. When deactivated, the lower back muscles lose part of the “corset” that they’re supposed to work together with. They have to work harder, then, to stabilize the spine and maintain posture as you rotate. This can cause chronic muscle tension on the side of the deactivated oblique. After years of this, tight muscles on one side of the spine can encourage misalignment of the vertebrae, leading to disc degeneration.
The original finding of the study is that sitting cross-legged exerts pressure on the sacroiliac (SI) joint, which forms where the hip bone meets the base of the spine, via elongation of the piriformis muscle, which stretches from the top of the thigh bone to the base of the spine. The study found that the piriformis was nearly 12% longer when sitting cross-legged compared to a neutral sitting position and over 21% longer than when standing. This elongation caused compression of the SI joints. See more on the study at www.ncbi.nlm.nih.gov.
SI joint dysfunction results when the joint is allowed either too much or too little motion. It usually causes sharp pain that may radiate into the buttocks. The pain is exacerbated by putting weight on the leg on the side of the affected joint. The study suggests that crossing your legs while sitting can cause changes in the length of the attaching piriformis muscle that make the joint hypomobile, thereby promoting lower back pain.
It may not give you heart disease or cancer, but sitting with your legs crossed can destabilize your pelvis and lead to lower back pain. Whether sitting or standing, it’s best to keep your pelvis in a neutral position; this promotes proper posture and cooperative muscle activation.