Low trait openness can make it difficult to cope with change. Low trait conscientiousness may be associated with externalised behaviour patterns. Overcontrolling parenting increases the likelihood of childhood behavioural problems. Conversely, autonomy-supporting parenting can improve children’s psychological strength. People born preterm can have more socially withdrawn personalities.

Rates of “Type D” personality amongst people with multiple sclerosis match the general population (around 16%) but having Type D personality traits might exacerbate multiple sclerosis symptoms.

Low trait openness may make accepting change difficult, so adaption should be easily implemented and gradual.

Be reactive to future health events to mitigate the likelihood of equipment changes

Designing to account for low conscientiousness and externalised behavioural problems should include consideration of safety factors and planning for expected misuse.

Encourage the rider’s parent or caregiver to use autonomy-supporting strategies by making the design safe including reducing the likelihood of injury to the rider while using the device

Be inherently autonomy-supporting by acting to maximise the independent function of the individual.

There is no evidence of common personality types amongst people who use specialised wheelchair seating. There is weak evidence of reduced trait openness across predominant health conditions associated with specialised wheelchair seating.

De Clercq, L. . E. et al., 2021. Parenting and Child Personality as Modifers of the Psychosocial Development of Youth with Cerebral Palsy. Child Psychiatry & Human Development.

Fatigue can reduce motivation, alertness, and active muscle force. Social stigmas surrounding physical impairment persist and can be demotivating, lower self-concept, and aggravate fatigue. In turn, lowered self-concept and self-efficacy are associated with less social participation and less health-related quality of life. People with congenital conditions generally have greater self conept and life satisfaction than those with acquired conditions.

Be durable, easy to repair or replace, and be useful with less input from wheelchair services or specialised knowledge

Include easily adjustable postural support to facilitate different social situations, levels of self-concept, and activities

Not overly occlude a rider’s appearance and clothing.

Around 30% to 50% of people who use specialised wheelchair seating are affected by substantial fatigue.

Bogart, K. R., 2014. The Role of Disability Self-Concept in Adaptation to Congenital or Acquired Disability. Rehabilitation Psychology, 59(1), pp. 107-115.

Khan, F., Amatya, B. & Galea, M., 2014. Management of fatigue in persons with multiple sclerosis. Frontiers in Neurology, Volume 5.

Kluger, B. M., Krupp, L. B. & Enoka, R. M., 2013. Fatigue and fatigability in neurologic illnesses. Neurology, 80(4), pp. 409-416.

Spuling, S. M., Wolff, J. k. & Wurm, S., 2017. Response shift in self-rated health after serious health events in old age. Social Science & Medicine, Volume 192, pp. 85-93.

Circadian rhythm disorders, Insomnia, sleep apnoea, and daytime fatigue can impede attention, processing speed, and recall – sleep apnoea can also present direct health risks. Sleep disorders can cause sleep deprivation and psychological exhaustion.

Be robust and remain safe after accidental damage

Make user-product interactions and operations intuitive

Be reliable and easy to repair

Remain functional in a variety of different outdoor climates to promote sleep hygiene

Around 30% to 50% of people who use specialised wheelchair seating are affected by a sleep disorder(s).

Hulst, R. Y. et al., 2021. Sleep problems in children with cerebral palsy and their parents. Developmental Medicine & Child Neurology.

Sankari, A. et al., 2019. Impact Of Spinal Cord Injury On Sleep: Current Perspectives. Nature and Science of Sleep, Volume 11, p. 219–229.

Hughes, A. J., Dunn, K. M. & Chaffee, T., 2018. Sleep Disturbance and Cognitive Dysfunction in Multiple Sclerosis: a Systematic Review. Current Neurology and Neuroscience Reports, 18(2).

Anxiety or depression disorder are the most prevalent psychological disorders and can have a reciprocal relationship with chronic pain and fatigue and create barriers to participation. These disorders can be especially difficult to diagnose and treat for people with intellectual or communication impairment.

Minimal weight and size for accessibility

Reduce sources of pain or discomfort using ergonomic design

Have good reliability with reduced downtime: meaning that repairs can easily be completed, to assist with social inclusion and participation.

Reduce the stress and inconvenience associated with breakdown

Have low centre-of-mass, to reduce impact on wheelchair drive performance and in particular traction performance, that will improve safety and comfort during outdoor use

Reduce the risk of injury from self-harm behaviours and be robust to withstand sustained self-harming behaviours.

Around 20% of people with health conditions associated with specialised wheelchair seating are affected by psychological disorder (greater than the general population)

Smith, K. et al., 2019. Risk of Depression and Anxiety in Adults With Cerebral Palsy. JAMA Neorology, 76(3), pp. 294-300.

Whitney, D., Warchausky, S. & Peterson, M., 2019. Mental health disorders and physical risk factors in children with cerebral palsy: a cross-sectional study. DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Volume 61, p. 579–585.

Marrie, R. A. et al., 2015. The incidence and prevalence of psychiatric disorders in multiple sclerosis: A systematic review. Multiple Sclerosis Journal, 21(3), p. 305–317.

visuo-spatial deficits can result in reduced reaction times and errors in trajectories

A visual perceputal impairment reasonably predicts driving ability.

People with cerebral palsy are generally less sensitive to mechanical and thermal stimuli but more sensitive to pain stimuli.

Comfort is a multisensory perception influenced by microclimate, vibration, appearance, time, and spatial tactile characteristics.

Maximise durability and reliability

Reduce the likelihood of injury following collisions

Minimise spatial envelope to reduce the likelihood of collisions

Reduces the magnitude of external variation in pitch and roll angles that can affect perception

React dynamically to movements applied, including vibrations

Manage microclimates at the seating interface vii. Look and feel comfortable.

At least 50% of people with health conditions associated with specialised wheelchair seating may have tactile registration and spatial tactile perception deficit.

Around 20% to 50% of people with health conditions associated with specialised wheelchair seating may be affected by visual spatial perceptual deficit.

Clementine, B., Traverse, E., Granger, E. & Mercier, C., 2021. Somatosensory deficits and neural correlates in cerebral palsy: a scoping review. Developmental Medicine and Child Neurology.

Krasniuk, S. et al., 2019. Clinical Determinants of Fitness to Drive in Persons With Multiple Sclerosis: Systematic Review. Archives of Physical Medicine and Rehabilitation, Volume 100, pp. 1534-1555.

Ego, A., Lidzba, K., Brovedani, P. & Belmonti, V., 2015. Visual–perceptual impairment in children with cerebral palsy: a systematic review. DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Volume 57, pp. 46-51.

Reduced proprioception causes reduced postural control and balance and possibly even altered skeletal structuring. Proprioception is plastic and can be improved through physical therapy and training. Upper limb proprioception deficits affect initiation of limb movement, speeds, trajectories, and paths.

To Facilitate outdoor activity that could in turn provide a means to train proprioception and balance.

Around 50% to 75% of people with health conditions associated with specialised wheelchair seating will be affected by proprioception impairment.

Clementine, B., Traverse, E., Granger, E. & Mercier, C., 2021. Somatosensory deficits and neural correlates in cerebral palsy: a scoping review. Developmental Medicine and Child Neurology.

Kuczynski, A. M., Kirton, A., Semrau, J. A. & Dukelow, S. P., 2021. Relative independence of upper limb position sense and reaching in children with hemiparetic perinatal stroke. Journal of Neuroengineering and Rehabilitation, 18(80).

Kuczynski, A. M. et al., 2017. Sensory Tractography and Robot-Quantified Proprioception in Hemiparetic Children with Perinatal Stroke. Human Brain Mapping, Volume 38, p. 2424–2440.

Paillard, T., 2017. Plasticity of the postural function to sport and/or motor experience. Neuroscience & Biobehavioral Reviews, Volume 72, pp. 129-152.

Dysarthria, anarthria, or aphasia may all occur and can impact participation and communication.

Aphasia often co-occurs with non-verbal impairments in attention, working memory, executive function, and reaction times

Improving sitting posture can potentially improve speaking qualities

Technical adjustment takes place quickly and easily – in order not to erode critical communication time

Around 50% of people with health conditions associated with specialised wheelchair seating have a motor disorder affecting speech, such as dysarthria. Around 30% of children with cerebral Palsy are non-verbal whilst 85% of children with dyskinetic cerebral palsy are non-verbal.

Julien, M. et al., 2021. Immediate effects of postural repositioning on maximum phonation duration tasks in seated individuals with acquired dysarthria: a pilot study. Disability and Rehabilitation

Aerobic exercise training increases cardiorespiratory endurance. The decision to Sustain exercise involves planning and goal-orientated logic and must also override discomfort. People with severe cerebral palsy are recommended to incorporate short periods of light intensity exercise into their day.

Ease of removal or adjustment of postural supporting devices.

To facilitate transfers, or change of posture, to allow for frequent interruptions to sedentary activity.

Assist the rider to feel more comfortable performing exercise

Manage or make acceptable temperature and humidity changes at the supported surfaces during exercise

Manage or make acceptable dynamic loading patterns during exercise activity.

Unable to estimate the prevalence of people who use specialised wheelchair seating with impaired exercise tolerance. Physiological impairment has been associated with pre-frontal cortex changes; an area also associated with MS fatigue.

Jaeger, S. et al., 2019. Multiple sclerosis–related fatigue: Altered resting-state functional connectivity of the ventral striatum and dorsolateral prefrontal cortex. Multiple Sclerosis Journal, 25(4), p. 554–564.

Robertson, C. V. & Marino, F. E., 2016. A role for the prefrontal cortex in exercise tolerance and termination. Journal of Applied Physiology, Volume 120, p. 464–466.

Risk of joint contracture, or reduced range of movement, becomes greater with age. Knee flexion contracture is mostly attributable to hamstring shortening amongst children with cerebral palsy. There is linear decline in available knee extension, popliteal angle, upper limb range, and hip abduction between birth and 15 years old amongst children with cerebral palsy. When hamstring length is fixed, over-extending the knee will act to extend the hip by between 2- and 4-times greater angle magnitude and torque, due to the muscle moment arm ratios.

Account for the rider’s reaching limitations, for example, by allowing for varied positioning of tray tables or specialised equipment for powered wheelchair driving

Minimise the thickness, meaning the concentric distance from the transverse thorax to the lateral surface, of the thoracic lateral support device

Design should be based on range of movement limitation per degree of freedom per joint

Account for asymmetric limitations in either hip flexion or knee extension, through a design that is easily adjustable with independent adjustment of body segment supports, and responsive to postural changes.

Include foot support, independent of the wheelchair foot support, that can adjust in-line with adjustments in hip flexion angle and can be adjusted in three dimensions to account for ankle contractures.

Facilitate transfers - including standing transfers and side transfers when there is hamstring contracture.

Facilitate easier identification of pelvic deviations in sitting that can occur due to hamstring contracture.

70% of people with severe cerebral palsy have an upper limb contracture. 30% of adults with severe cerebral palsy may have wind sweeping contracture. 20% of adults with severe cerebral palsy may have less than 90 degrees hip flexion and asymmetrical range of hip flexion.

Ágústsson, A., Sveinsson, Þ. & Rodby-Bousquet, E., 2017. The effect of asymmetrical limited hip flexion on seating posture, scoliosis and windswept hip distortion. Research in Developmental Disabilities, Volume 71, pp. 18-23.

Hedberg-Graff, J., GRANSTROM€, F., ARNER, M. & KRUMLINDE-SUNDHOLM, L., 2019. Upper-limb contracture development in children with cerebral palsy: a population-based study. Developmental Medicine and Child Neurology, Volume 61, p. 204–211.

Nordmark, E. et al., 2009. Development of lower limb range of motion from early childhood to adolescence in cerebral palsy: a population-based study. BMC Medicine, 7(65).

Weak muscles have reduced functional capacity. Accelerated musculoskeletal aging reduces muscle strength prematurely for people with cerebral palsy. Spastic muscles are weaker than non-spastic muscles. Some spasticity treatments can also further weaken muscles. Very weak muscles generally cannot be rehabilitated by resistance training.

Have variable fit to account for muscle atrophy

Facilitate changes in body position – for independent pressure and pain management

Maintain body position during dynamic activities such as powered wheelchair driving

Almost all people who use specialised wheelchair seating will have reduced functional muscle power in one or more major muscle groups.

Smith, L. R. et al., 2011. Hamstring contractures in children with spastic cerebral palsy result from a stiffer extracellular matrix and increased in vivo sarcomere length. The Journal of Physiology, 589(10), p. 2625–2639.

Verschuren, O. et al., 2018. Determinants of muscle preservation in individuals with cerebral palsy across the lifespan: a narrative review of the literature. Journal of Cachexia, Sarcopenia and Muscle, Volume 9, p. 453–464.

Neither spasticity nor prolonged inactivity are likely to be the true, or only, cause of intrinsic muscle contractures.

Soft tissue changes can be misinterpreted as spasticity and might be more prevalent amongst people with hypertonic cerebral palsy than spasticity

Spastic dystonia may be a greater risk factor for postural asymmetry and contracture, than spasticity, on account of the persistant, velocity-independent, and spontaneous nature of spastic dystonia.

Adjustment that accounts for muscular contracture or future contracture - React dynamically to dynamic stresses such as those applied by dyskinetic movement patterns

Ensure a good fit when sitting posture is asymmetrical (for pressure and pain management and safety factors)

Be robust to support riders with chronically high or variable muscle tone (that place greater forces on equipment than the passive body weight force)

All people who use specialised wheelchair seating will have muscle tone disorder in one or more major muscle groups, with hypertonia being the commonest phenotype.

Lieber, R. L. & Fridén, J., 2019. Muscle contracture and passive mechanics in cerebral palsy. Journal of Applied Physiology, Volume 126, p. 1492–1501.

Lumsden, D. E., Gimeno, H., Elze, M. & Tustin, K., 2016. Progression to musculoskeletal deformity in childhood dystonia. European Journal of Paediatric Neurology, 20(3), pp. 339-345.

Trompetto, C. et al., 2020. Ghost spasticity in multiple sclerosis. Journal of Electromyography and Kinesiology, Volume 51.

Spasticity, dyskinesia, and tremor can impede functional activity and sitting balance.

The effectiveness of specialised wheelchair seating should be measured by the ability to maintain posture and equilibrium.

Maintain a localised and functional pelvis position during and after dynamic loading

Improve the rider’s functional performance

Be robust to lapses in control

All people who use specialised wheelchair seating have reduced control of voluntary movement. Around 30% of people with severe cerebral palsy will have the dyskinetic phenotype.

Grillner, S. & El Manira, A., 2020. Current Principles of Motor Control, with Special Preference to Vertebrate Locomotion. Journal of Physiological Reviews, Volume 100, pp. 271-320.

Li, S. et al., 2019. A Unifying Pathophysiological Account for Post-stroke Spasticity and Disordered Motor Control. Frontiers in Neurology, 10(468).

Immobility, incontinence, altered microclimates around skin sites, obesity, stoma, and contracture are risk factors for moisture associated skin damage.

Wet skin has a higher coefficient if friction than dry skin.

Pressure ulcers remain life threatening. Impaired mobility and impaired sensation are risk factors for pressure ulcers. The sacrum is the region at greatest risk of breakdown. An individual’s risk of pressure ulcers changes over time.

Ability to quickly provide, setup, and modify the device

To promote health, wellbeing, and safety

To fit riders with asymmetrical postures

Facilitate toileting. identification of wetting or soiling, and cleaning

Friction forces, edges, and pressure gradients should not provoke abrasion or wounds

Reduce intertrigo risk by aerating skin fold sites

Maximise heat evacuation when the wheelchair is in motion

Include means of assisting body movements for pressure relief

All people who use specialised wheelchair seating are at risk of pressure ulcers and moisture associated skin damage. Around 80% of pressure ulcers sustained by people with mobility impairments occur at the pelvis region. The likelihood of acquiring a pressure ulcer is greater for those with spinal cord injury or spina bifida than for those with multiple sclerosis or cerebral palsy, however, the severity of outcome may be greater for those with multiple sclerosis.

Mitchell, A. & Hill, B., 2020. Moisture-associated skin damage: an overview of its diagnosis and management. British Journal of Community Nursing, 25(3).

Gefen, A. et al., 2021. Our contemporary understanding of the aetiology of pressure ulcers/pressure injuries. International Wound Journal, pp. 1-13.

Sprigle, S., McNair, D. & Sonenblum, S., 2020. Pressure Ulcer Risk Factors in Persons with Mobility-Related Disabilities. Advances in Skin & Wound Care, 33(3), pp. 146-154.

Intellectual impairment is a greater risk factor for incontinence than motor impairment. Constipation is common and a source of pain. Urinary tract infection can be common especially for people with multiple sclerosis. Incontinence associated dermatitis is a high risk for people who are faecally incontinent or both urinary and faecally incontinent.

Anticipate urine or faecal contact

Design for ease of regular cleaning and remain hygienic after cleaning

Facilitate use of a toileting bottle as required

Around 90% of people with severe cerebral palsy may be urinary incontinent, 85% may be faecally incontinent. Around 50% of people with multiple sclerosis may be urinary incontinent while 15% may be faecally incontinent. Around 40 to 50% of people with health conditions associated with specialised wheelchair seating may suffer from constipation.

Wright, A. J., Fletcher, O., Scrutton, D. & Baird, G., 2016. Bladder and bowel continence in bilateral cerebral palsy: A population study. Journal of Pediatric Urology, 12(6).

Khan, F., Pallant, J. F., Shea, T. L. & Whishaw, M., 2009. Multiple sclerosis: prevalence and factors impacting bladder and bowel function in an Australian community cohort. Disability and Rehabilitation, 31(19), p. 1567–1576.

Risk factors for neuromuscular scoliosis in cerebral palsy include severity of health condition, reduced knee extension, reduced hip abduction, pelvic obliquity, growth spurts, trunk muscle imbalance, asymmetric hip flexion. Proprioception impairment was identified as a candidate risk factor not yet well researched.

One path to scoliosis originates with knee flexion contracture, then lying postures associated with knee flexion contracture, then hip adduction contracture, sometimes with hip subluxation or dislocation, then pelvic obliquity, then scoliosis.

Only surgery and, for Duchenne muscular dystrophy, steroid treatment, are effective treatments for neuromuscular scoliosis. Claims of health benefits of using specialised seating for scoliosis remain under researched. Nevertheless, specialised wheelchair seating remains a vital tool for accessing a wheelchair for people with severe neuromuscular scoliosis.

Focus on management of pelvic obliquity. - shift from the concept of the idealised, prescribed, posture towards a model that is versatile, permissive, and reactive.

The rider remains balanced and comfortable during outdoor usage

Postural support performance should be measured against the therapist’s hands

Pelvic support should be measured in terms of ability to maintain pelvis position over time, under vibration, and during functional movement.

By age 20, 70% of people with severe cerebral palsy (being GMFCS V) have scoliosis with Cobb angle above 40˚. Without treatment, almost all people with Duchenne Muscular Dystrophy develop scoliosis once they become non-ambulatory.

Around 20% of people develop scoliosis after spinal cord injury, with Cobb angles ranging from 13-28˚.

Yoshida, K., Kajiura, I., Suzuki, T. & Kawabata, H., 2018. Natural history of scoliosis in cerebral palsy and risk factors for progression of scoliosis. Journal of Orthopaedic Science, Volume 23, pp. 649-652.

Ágústsson, A., Sveinsson, Þ. & Rodby-Bousquet, E., 2017. The effect of asymmetrical limited hip flexion on seating posture, scoliosis and windswept hip distortion. Research in Developmental Disabilities, Volume 71, pp. 18-23.

Vialle, R., Thévenin-Lemoine, C. & Mary, P., 2013. Neuromuscular scoliosis. Orthopaedics & Traumatology: Surgery & Research, 99(1), pp. 124-139.