# The State of the Art of Biomechanics Applied in Ergonomic Furniture Design
## 3 Findings and Discussions
### Biomechanical Analysis and Testing Methods
#### 3.2.2 Computer-Aided Ergonomics  
Due to the complexity of human body systems, simple models often have difficulty explaining complex problems in practical applications. This has led to the development of human biomechanical models in the direction of complexity and detail, with simulation playing an increasingly important role as a necessary means to solve the described complex problems [73]. In recent years, computer modeling and simulation technology have developed to a new high level, and this approach can provide a more quantitative explanation of how the neuromuscular and musculoskeletal systems interact to produce motion. In particular, simulations of standing, walking, jumping, and pedaling can provide insight into how the leg muscles work together in each task to achieve a common goal [31; 75]. The primary simulation software utilized comprises LifeMOD, OpenSim, AnyBody Technology, VIMS, SIMM, and ANSYS finite element software [79; 80; 81; 82; 83; 84; 85]. Among them, the skeletal muscle model of VIMS software cannot define the muscle unit that generates the key dynamic force, so it is mainly used for kinematic analysis. SIMM software is mainly used to study joint kinematics and the characteristics of muscle forces and moments, and it can represent the kinematic characteristics of joints, but the kinematic model of joints is not directly available in SIMM. LifeMOD, Opensim, and AnyBody Technology are the three most widely used human simulation software programs. Table 1[80] summarizes their main features.  
LifeMOD is a common simulation software for gait analysis [86; 87; 88], which can study the changes in human biomechanical parameters and the coupling between human and mechanical systems [89; 90] under different working environments [86; 91; 87; 92; 88; 89; 93].  
Opensim has fine control over muscle morphological parameters, low computational error, and fast computation [94,95], and it is used in many other fields, such as walking dynamics analysis [96], motion performance studies [97, 98, 99, 100], surgical procedure simulation [92,101], and medical device design [87,88,94,102].  
AnyBody Technology is the most complex but most functional muscle and bone modeling software tool currently available [48, 99, 103, 49, 50, 75, 97, 103], which can customize the parameters related to the human body model and directly invoke the human body model from the model database. It can model the environment in the simulation and interface with the presence of other software (such as SolidWorks, ANSYS, Abaqus, etc.) [104,105]. It is widely used in research fields, such as clinical medicine [48,106,107], automotive industrial design [58], aerospace, rehabilitation medical engineering [92,108], product design [24, 25, 26, 36], work environment design [35,49], and sports and equipment [109,110].  
In addition to the abovementioned simulation software, software such as MATLAB and FEM are used in furniture design [56,57,98]. The main technical challenges faced in current human biomechanics-based modeling and simulation research are (1) how to accurately calculate joint muscle forces and accuracy verification problems; (2) kinetic parameters in human motion derived from kinematic data; and (3) neuromuscular multi-structural hierarchy and multiscale control of motion biomechanics modeling. In the future, the following directions are likely to be the key directions for sports biomechanics modeling and simulation research: (1) Personalized musculoskeletal modeling and analysis--with the rapid development of new sensor technologies, the research of personalized musculoskeletal modeling means and analysis and evaluation methods that reflect individual differences will become a trend. (2) Neuromuscular control simulation--with the continuous development of computer technology, the study of neuromuscular model control based on deep learning and reinforcement learning strategies is expected to become a research hot topic in the crossover field.