Free shoulder space requirements in the design of high backrests

Effect of office chair design features on lumbar spine posture, muscle activity and perceived pain during prolonged sitting

Chair design features are typically compared using multiple seats, which can lead to confounding effects. Using a single chair, configurable to four designs (control, lumbar support, seat pan tilt and scapular relief), we investigated the effect of chair design on spine posture and movement, muscle activity and perceived pain in a sample of 31 asymptomatic adults. A total of 39% of the population were classified as pain developers, having significantly higher peak pain levels across most body regions. The lumbar support and seat pan tilt condition resulted in more neutral spine and pelvic postures. Greater muscle activity was found in the seat pan condition and non-pain developers displayed lower spine muscle activation levels overall. Despite some improvements in spine posture, sitting-induced pain was present in the study sample at similar proportions to those reported previously. Future studies may consider investigating interventions targeted to sitting-induced pain developers as opposed to the general population. Practitioner summary: Four office chair configurations were tested. The lumbar support and seat pan tilt conditions resulted in the most neutral back posture but did not mitigate the clinically significant levels of sitting-induced pain experienced by a large portion of the tested sample. Future work should target interventions to these individuals.

Neck posture and muscle activity in a reclined business class aircraft seat watching IFE with and without head support

The purpose of this study is to research if a headrest benefits the comfort of the passenger and lowers muscle activity in the neck when sitting in a reclined (slouched) posture while watching in flight entertainment (IFE) in an aircraft business class seat. No significant differences in muscle activity in the musculus sternocleidomastoid and musculus trapezius pars descendant were found between the conditions with headrest and without headrest. A significant difference in expected comfort rating was found. Subjects indicated they expect to experience more comfort with a headrest when watching IFE for a duration of two movies during a long-haul flight. This study also found a significant difference in posture. In the condition without headrest the head was more upright compared to the condition with headrest. The lack of significant difference in muscle activity and the significant difference in posture may indicate that humans tend to look for a head position that is neutral, in the sense of minimal muscle effort. This study shows that the use of a headrest may benefit the comfort experience of the passenger during flight. However, further research is necessary on the design of the headrest and the long-term effects of head support on comfort, discomfort, muscle activity and fatigue for watching IFE in a slouched posture.

Características biomecânicas, ergonômicas e clínicas da postura sentada: uma revisão

A posição sentada é a mais adotada nos ambientes de trabalho, na escola e nas atividades de lazer. Porém, a manutenção prolongada dessa posição ocasiona a adoção de posturas inadequadas e sobrecarrega as estruturas do sistema musculoesquelético, o que pode acarretar dor e lesão na coluna lombar. A presente revisão teve como objetivo identificar os fatores biomecânicos, ergonômicos e clínicos envolvidos na sustentação da postura sentada. Para isso, foram consultadas as bases de dados ISI Web of Knowledge, Medline, Pubmed e EBSCO Host, sendo selecionados 72 artigos publicados entre 1965 e 2010. Foi possível identificar que na posição sentada não existe uma postura ideal a ser sustentada, mas algumas posturas são mais recomendadas do que outras, tal como a postura sentada ereta e a postura lordótica. As cadeiras influenciam o padrão da posição sentada: conforme seu design, pode permitir maior variedade de posturas. Modificações na cadeira e a utilização de exercícios para o aumento da resistência muscular e da propriocepção, bem como a reeducação postural, são intervenções úteis para reduzir o impacto causado pela posição sentada prolongada no sistema musculoesquelético.