**1. The concepts and basis of biomechanics**

The achievement of the human voluntary movement is seemingly simple, but rather it is considerably complex. As it is a very complex mechanism which allows many nerve structures to make decisional and/or reflexional choices, then this mechanism "defines" and "controls" the movement, through the nerve impulses intended for the musculoskeletal system. In the human body, around 640 muscles are involved with 213 bones rigidifying several segments ranging from a few cm3 to several thousand cm3 through more than 100 joints. The whole system thus allows greater than 100 degrees of freedom. Biomechanics study the complexity of the human body through behavior and performance in daily life with respect to musculoskeletal system with the aim to optimize the system [1, 2]. This discipline seems essential in today's world and considerably promising for the future. Indeed, the concepts, methods, and analytical techniques that we use to characterize human mechanics represent major economic stakes**.** The development is necessarily inscribed in a vision of interactions between the physical sciences (metrology, complex mechanical and electronic systems), information sciences and technologies, and life sciences (materials, tissues, organs, and limbs) [3–8]. The ambition of the research work carried out in biomechanics is to improve the performance of high-level athletes and the comfort and quality of life of patients and to minimize stress on joints in real-field or laboratory situations. Biomechanics is subdivided into kinematic (**Figure 1**) and kinetic (**Figure 2**) analyses. Kinematics is concerned with the analysis of motion (e.g., to determine the forces applied to a joint from the inverse dynamics), while kinetics studies the forces that cause or result from it (e.g., the reaction of the ground when walking).

**Figure 1.** *Kinematic device for 3D motion analysis. The example of a patient with myopathy.*

**Figure 2.**

*Kinetic analysis of motion. Correlation between modeled and experimental data.*
