Chris Daniel
Glan Conwy, Conwy, UK
Advertisement
The reason that cross-legged sitting is comfortable is that it allows the trunk to be held in an upright position with relatively little effort.
In a standing posture, the pelvis is rotated slightly forwards, giving the spine an 鈥淪鈥� shape with an inward curve of the lower back (lumbar lordosis), an outward curve of the upper trunk (thoracic kyphosis) and a further inward curve at the neck (cervical lordosis). When we sit with our legs out straight or on a chair with knees flexed and feet on the floor, the pelvis rocks backwards. This flattens the lumbar curve, causing the whole spine to take on a 鈥淐鈥� shape, which requires effort to correct. As the muscles fatigue, the position becomes increasingly uncomfortable.
In cross-legged sitting, the thighs are angled outwards and rotated at the hips while the knees are fully flexed and the lower legs crossed. This has the effect of shortening the hip extensor muscles, such as the glutei and the hamstrings, reducing their tendency to pull the pelvis backwards. This makes it easier for the hip flexor muscles, such as the rectus femoris and iliopsoas on each side, to hold the pelvis upright. This makes a good sitting position easier to maintain.
Sitting in any fixed position for too long isn鈥檛 advisable. Crossing the legs can strain the joint ligaments and cause blood to pool due to constriction of the veins. When blood is allowed to flow again, it can be painful for a few seconds, but this might be a small price to pay for the benefits of good posture.
@keshavrajgopal via Twitter
Bad? In India, sitting cross-legged is often the default sitting posture if there is no sofa or chair. Many, especially those who practise yoga, can sit like this for hours without getting uncomfortable.
@suraj1245789 via Twitter
What? Bad? In Sanskrit, we Indians call it asana. We practise it often. It is recommended to sit on the floor with crossed legs while eating.
To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
麻豆传媒 retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
You can also submit answers by post to: The Last Word, 麻豆传媒, 25 Bedford Street, London WC2E 9ES.