# The State of the Art of Biomechanics Applied in Ergonomic Furniture Design
## 3 Findings and Discussions
### Biomechanics Utilized in Different Types of Furniture
#### 3.1.2 Special Furniture  
Approximately 1% of the world's population uses wheelchairs [43]. A wheelchair is a type of specialized furniture product for people with physical disabilities that is used for mobility, social participation, and healthy living. For manual wheelchair users, maneuvers such as turning, going uphill, and passing curbs are difficult, and they use their upper extremities for prolonged periods, putting them at risk of injury from upper extremity use [44; 45; 46]. Therefore, the primary goal of incorporating biomechanical principles in the design of specialized furniture, such as wheelchairs, is to mitigate the risk of physical harm to users and enable them to independently perform daily activities. Differences between surfaces highlighted the importance of assessing wheelchair propulsion capabilities on a range of surfaces through a kinetic analysis of manual wheelchair propulsion during activation on selected indoor and outdoor surfaces [45]. Wearable sensors were installed on the wheelchair to track the wheelchair user throughout their weekly motion. Based on the monitoring results, the efficiency of wheelchair use can be optimized in future wheelchair design in terms of wheelchair-user interaction principles [46; 47]. [PERSON] et al. [48] validated an upper extremity model for manual wheelchair users to reduce upper extremity injuries during use. The use of electric drives has become a new development in personal transportation. The wheelchair with cam-thread drive (WCD) is a new type of electric wheelchair. Field tests, laboratory measurements, and biomechanical analysis of the WCD and comparison with a typical wheelchair with push-rim drive (WPD) revealed that the WCD is a sustainable form of personal transportation that requires less human biological force to propel and exerts less stress on the human motor system, and therefore, can be used for rehabilitation [49]. The world's population is aging at an irreversible rate. For most elderly people, daily activities such as sit-to-stand transitions and walking pose significant challenges for most elderly individuals. Previous commercially available sit-to-stand assistive devices are relatively large and require sufficient upper limb strength for use, making them unsuitable for elderly people with declining physical functions [20; 50]. The utilization of biomechanics, such as the abovementioned research on wheelchairs, can reduce upper extremity injuries and help users perform independent behaviors such as sit-to-stand transitions in daily living. To this end, some researchers have developed active walker systems [51], user-adaptive support systems [52], etc. The parameters of this user adaptive support system are determined according to the user's physical dimensions and disability and illustrate the effectiveness of the method of adjusting the position of the handrail, the height of the bed and the position of the feet. According to the survey, falls are the leading cause of accidental injury and death among older adults. Nearly 24% of falls in the elderly are caused by falling out of bed. According to biomechanical evaluation, protective floor mats can reduce the risk of injury from falls bed to some extent [53; 54]. The increase in the elderly population has led to a significant increase in the number of nursing homes and an increase in the demand for caregivers. Wearable lower extremity assistive devices and stretchers with assistive features aim to reduce the physical burden on caregivers and family members of patients [55; 56]. As stated above, the primary objective of using specialized furniture in biomechanics is to aid users in reducing upper limb injuries and facilitating their fundamental daily activities in a secure setting [31]. At the same time, it reduces the physical burden on caregivers when caring for the patient. The use of biomechanics in the design of special furniture is relatively mature.