# The State of the Art of Biomechanics Applied in Ergonomic Furniture Design
## 3 Findings and Discussions
### Biomechanics Utilized in Different Types of Furniture
#### 3.1.1 Common Furniture  
Seating furniture is a commonly used and highly interactive type of furniture in daily life. This interaction is typically experienced on a one-to-one basis with the furniture. Therefore, the application of biomechanics in furniture design is mainly focused on seating furniture. Many efforts have been made to improve the anthropometry and ergonomics of seating furniture from the perspective of human-furniture interactions to improve the comfort of sitting and human health [20]. The subjective evaluation of the user can only provide qualitative information. Analyzing the human-seat interface and understanding the influence of body weight distribution on seat comfort are beneficial for ergonomic and functional seat design [21]. A method for measuring the pressure distribution on the contact surface is one of the most widely used means to analyze the biomechanics of human  
Figure 4: The research methodology and organizing frame of this study for determining the role of biomechanics in furniture design. sitting from an objective point of view [22]. The design of the seat support can decrease the user's muscle fatigue level during extended use, suggesting that biomechanical analysis of the subject can account for the level of comfort experienced. [23]. A study showed that the most important design parameter affecting seat comfort is the backrest angle and that the inclination of the seat pan and the friction coefficient have a complex combination of effects on muscle activity and spinal joint forces [20; 24; 25; 26; 27]. Increasing the backrest angle from 90\({}^{\circ}\) to 105\({}^{\circ}\) decreases the reaction forces between L5 and the sacrum. As a result, muscle activation is significantly reduced, which is an important factor in increasing the overall comfort value [20; 27; 28]. This study also showed that women are more suitable than men to use lightweight armchairs. A synchronized seat significantly reduces lumbar lordosis when the backrest is tilted [24]. However, continuous lordosis sitting is more detrimental to lumbar spine health than anterior lordosis sitting and may lead to cumulative damage to the soft tissues of the spine [20; 29]. Similarly, studies have shown a linear relationship (or correlation) between upholstery thickness and seat comfort [21]. To obtain more qualitative information about what is happening inside the participant's body, [PERSON] et al. [30] conducted human digital modeling and rapid upper limb assessment (RULA) analysis of office chairs, with the aim of improving the safety of office seating and improving the user's physical health and well-being at work. However, sitting comfortably is not the same as sitting healthily, and sitting at a computer for long periods can lead to static loading on the body [31]. Therefore, by monitoring posture, muscle activity, and spinal contraction in women typing on an office chair with armrests and an exercise ball, it was found that the advantages of the body load sitting on an exercise ball may not outweigh the disadvantages [32]. Furthermore, researchers with expertise in biomechanics have examined common household furniture to better understand its impact in daily life. Lifting a child into or out of a motorized seat, bathtub, crib, infant carrier, and highchair has been reported to be a stressful activity for mothers [33; 34]. Therefore, when designing furniture for infants and toddlers, it is important to consider not only the suitability for infants and toddlers but also the health and comfort of their caregivers. One researcher analyzed the lumbar joint reaction forces and muscle activation in mothers as they lifted their babies out of the baby cribs designed with varying bed heights. The study established a milestone for the implementation of computer-aided ergonomic methods in furniture design [35]. In addition, the team evaluated the musculoskeletal stress levels associated with the use of two different types of kitchen furniture cabinets [36].