28 May Chair Design, Sitting & Health Research
Chair design, sitting and health. NCOR research
Sitting and health risks.
The risks of extended sitting to health are not new. There was a six fold increase in deaths from pulmonary embolism reported during World War 2 due to extended periods sitting in deckchairs in air raid shelters (Simpson 1940). Morris et al also identified the hazards in high levels of sitting in their study of London bus drivers in the 1950’s. More recent work has articulated a new condition: the E- thrombosis (blood clots from sitting too long in front of PC). Although advice is now tailored to reduce the amount of time we spend sitting to improve our posture and increase activity through the body while sitting.
Healey et al estimated that the average adult can spend between 50% to 60% of their day in sedentary activity (Healey et all 2011). Work undertaken by Wilmot et al, 2012 identified that excessive sitting was associated with an increased risk of 112% for diabetes, 147% increase for cardiovascular events, 90% risk of cardiovascular mortality and 49% increased risk of all-cause mortality. However in 2015 a study was published by Pulsford et al who reported their review in a cohort study. They concluded that the risks were less dramatic as in previous research but the participants in this study reported higher than average levels of daily activity so the findings should be treated with some caution (Pulsford et al, 2015)
Although the number of designs for different types of chairs is increasing, evidence to support their benefits is still growing and is largely based on small pilot studies. A summary of some of the studies relating to different chair designs is shown below.
Type of chair Overall findings
Kneeling chair Sacral slope and lumbar lordosis reduced in all participants between standing and sitting. There was less reduction in lumbar lordosis when sitting on a kneeling chair compared with a standard flat chair. This effect was present in CLBP patients and healthy subjects.
Balan’s chair The standard office chair was rated as more comfortable that the balan’s chair. Increased EMG readings were noted in the cervical and paraspinal muscles for the balan’s chair. Pedal blood flow was increased by 15% in the balans chair.
Kneeling chair The study suggested that ergonomic kneeling chair set at a 20˚ inclination maintained standing lumbar posture to a greater extent than when sitting on a standard computer chair.
Bambach saddle seat Low back discomfort ratings tended to increase over time irrespective of the chair being used. They were no differences in levels of productivity between the two chairs, but the saddle seat promoted a greater trunk to thigh angle for all subjects.
Sit – stand workstations The intervention group using the sit to stand desk recorded significantly decreased time in sitting positions (100 minutes) and increased standing time (99 minutes).
Experimental chair designed to aid user in The experimental chair provided more postural movement changing posture compared to the school computer chair.
Sit stand workstations, treadmill The data suggests that some amount of standing during an 8 hour workstations and bicycle workstations working day could be beneficial without having a detrimental effect on either comfort or productivity.
Stability balls Small changes to biological responses were reported for use between the two seating types. Increased discomfort was reported using the stability ball compared to the office chair.
Dynamic Vari-kneeler, the dynamic swopper, The researchers concluded that the saddle chair produced the the saddle chair and a standard office chair most appropriate posture in the lumbopelvic region, and the with back removed saddle and swopper for the cervical region. No chair consistently produced an ideal posture across all body regions but the saddle chair created the best posture among the four chairs investigated.
Above research was published by National Council for Osteopathic Research under heading Chair design and health- a summary table of evidence in December 2016.