The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Resting postures in human evolution: squatting, sitting, and the biomechanics of low back pain

KELSEY E. JELENC and DAVID A. RAICHLEN.

School of Anthropology, University of Arizona

March 27, 2015 , Archview Ballroom Add to calendar

In many contemporary cultures, people do not rest in chairs, but instead rest in squatting and floor-sitting postures. These “traditional” styles of rest appear in the hominin fossil record in the form of squatting facets on the distal tibia as early as 1.8 mya, suggesting chair-sitting is a relatively recent form of inactivity. Low back pain (LBP) is a common health problem linked with sitting in Western contexts, but is less prevalent among populations that rest in traditional postures. This study examines the link between rest and LBP by comparing back function in different resting postures. Based on recent work linking LBP with muscular atrophy of the erector spinae (ES), we hypothesized that traditional postures would elicit a more kyphotic lumbar curve and higher levels of ES activity, which could limit atrophy over time. Lumbar angle and ES activity were measured in ten subjects during periods of chair-sitting, floor-sitting, and squatting. Paired t-tests were used to compare variables between conditions. All sitting styles resulted in a kyphotic curvature of the lumbar spine. However, squatting elicited higher levels of ES activity than chair-sitting (p = 0.0156; 0.0078) which may help to keep the ES well-conditioned. In contrast, lower muscle activity during chair-sitting may cause atrophy of the ES over time, increasing vulnerability to LBP. Ultimately, these differences in muscle activity may help to explain the current cultural patterning of LBP. Since this study only included Western subjects, future work will examine lower back biomechanics in subjects who are experienced at squatting.

This project was supported by NSF BCS 1440867.