Empirical knowledge is lacking on reclined seating postures. To unify such data, a biomechanical model is needed that accurately predicts posture, the relative position of the pelvis, the point of load transfer to the seat, internal and external forces, and the motion paths of the support surfaces. The overall aim of this investigation was, therefore, to create and validate a biomechanical model of reclined seating postures, and to evaluate in vivo measured and predicted data. A two-dimensional biomechanical model was developed, validated and applied. A comprehensive set of biomechanical data was collected from fifteen gender and age diverse subjects to examine the foundational principles for reclined seating ergonomics. The model agreed with 98.8% of measured data on posture across the seated test conditions. There was a significant relationship between modelled and measured force (p < .001, r = .92), which improved after normalisation (p < .001, r = .97) with an 8% full scale error. The model was robust across height and gender. Significant differences in interface pressure (peak pressure, average pressure and area), stature, back muscle activity and spinal curvature were found between all of the seated test postures. Significant relationships were found between the model predictions and all of the experimental data. This research is unique in creating a framework around reclined seating postures which connects previously disparate areas of seating research. The biomechanical model, experimental results, and theories developed from this research have potential implications in research, and design, for applications including backcare chairs, seating for long-term care and patients with neuromotor deficits, wheelchairs and airline seating. Furthermore, this study exists at the interface of anthropometric and biomechanical modelling, and therefore may have cross over potential to digital humans, where their integration with biomechanical models is at the cutting edge of the field.

[pt] A imobilidade na postura sentada reclinada e as limitações no espaço da poltrona de viagens aéreas longas, somadas aos efeitos da pressão do peso do corpo sobre os tecidos levam o passageiro a uma acomodação na busca de conforto. Os constrangimentos músculo-esqueléticos conseqüentes podem provocar dores e desconforto nos usuários. Para estudar as causas dos constrangimentos foram vistos os dados sobre a postura humana, com ênfase na região sacro-lombar, assim como indicações de ergonomistas sobre cadeiras e as prioridades da aviação comercial. Os métodos usados na observação foram a revisão bibliográfica em autores de ergonomia, anatomia, cinesiologia. A assessoria de informante qualificado em interiores de aviões juntou-se à consulta a revistas especializadas na área da aviação comercial. Os resultados obtidos através da análise dos dados do questionário (n=115) confirmam o desconforto sentido pelos passageiros de viagens aéreas longas em regiões como pescoço (64,3 por cento), lombo-sacra (48,7 por cento) e pés (59,1 por cento). Inadequações como a largura do assento (58,3 por cento), o espaço para as pernas (50,4 por cento), o apoio do pescoço (47,8 por cento), e o apoio lombar (37,4 por cento) foram apontadas por estes usuários. As conclusões confirmam a hipótese O espaço limitado das poltronas aéreas e as conseqüentes posições assumidas pelos passageiros durante viagens aéreas longas acarretam constrangimentos posturais músculo-esqueléticos, e trazem como conseqüência desconforto e dores no pescoço, região lombar e pés, dormência e dores irradiadas nos usuários. As recomendações foram em relação à ergonomia da postura sentada para o apoio lombar, assento e posições de membros inferiores. Desdobramentos sugeridos foram a observação de passageiros durante a viagem, estudos sobre o sistema circulatório dos membros inferiores, constrangimentos posturais na região cervical e posterior da pelve. / [en] The lack of mobility in reclined sitting posture, the space limitations in seats in long distance flights along with the relief of pressure lead the passenger to scoop his hip forwards or to twist it. Consequent muscular and skeletal postural constraints may cause discomfort and pain on users. Searching for the reasons of constraints, human posture studies, ergonomics recommendations on chairs and aicraft priorities were seen. The study methods employed were a literature review on Ergonomics, Anatomies and Kinesiologists, aircraft interiors qualified informant and aircraft interiors specialized revues. A questionnaire was submitted to long flight passengers to search for body discomfort and inadequacies on seats. Data analysis (n=115) showed discomfort on neck region (63,3 percent), feet (59,1 percent) and low back (48,7 percent). Inadequacies on seats design such as width (58,3 percent), room for legs (50,4 percent), neck support (47,8 percent) and lumbar support (37,4 percent) were pointed by passengers. The hypothesis Lack of room in aircraft seats and the positions assumed during long distance flights cause postural constraints that lead to discomfort and pain on neck, low back and feet, numbness and irradiation on users was confirmed. Recommendations on lumbar support possibilities, height of seat and lower limbs positions were made. Suggestions like further observation of flying passengers, circulatory system and postural constraints on cervical and pelvic region were proposed.