What Is Biomechanics?

Biomechanics is a field of study concerned with the mechanics of biological systems, examining the forces, deformations, and motions that occur in living organisms and their constituent tissues, organs, and cells. It applies the principles of classical mechanics, including statics, dynamics, and continuum mechanics, to biological structures ranging from individual protein molecules to whole-body human movement. The field draws on anatomy, physiology, materials science, and engineering, and contributes to disciplines including orthopedics, sports science, rehabilitation medicine, and the design of devices that interface with the body.

Anthropometry, the systematic measurement of body dimensions and proportions, provides the geometric input data that biomechanical models require to represent human body segments accurately. Quantitative anthropometric databases have been essential for designing ergonomic equipment, protective gear, and medical implants that accommodate the variation in body size across human populations.

Kinematics and Dynamics

Kinematics in biomechanics describes the geometry and time evolution of biological motion without reference to the forces that cause it. Gait analysis, a common kinematic application, uses force plates, inertial measurement units, and optical motion capture systems to record joint angles, segment velocities, and center-of-mass trajectories during walking, running, or other tasks. These measurements are used to identify abnormal movement patterns associated with neurological conditions, orthopedic pathology, or injury risk. Dynamics analysis extends kinematics by incorporating the forces and moments acting on body segments, allowing computation of joint contact forces and muscle forces that cannot be measured directly in vivo. The International Society of Biomechanics maintains recommended reading lists and data standards that guide measurement methodology in this area. Inverse dynamics, which derives forces from measured motion, and forward dynamics, which simulates motion from specified forces, are the two primary computational approaches used in human movement studies.

Tissue and Material Mechanics

Biological materials such as bone, cartilage, tendon, ligament, and arterial wall exhibit mechanical behavior that differs substantially from engineering materials. They are anisotropic, meaning their properties depend on loading direction; viscoelastic, meaning their response depends on both the magnitude and rate of deformation; and often nonlinear, stiffening as deformation increases. Research published through PMC on mechanics of biological tissues reviews the experimental techniques and constitutive models used to characterize these materials. Bone is a hierarchically structured composite of mineral and collagen that provides high stiffness and fracture toughness, while soft tissues like articular cartilage serve as load-distributing interfaces between bones that must sustain millions of loading cycles over a lifetime. Understanding tissue mechanical properties is prerequisite to designing implants, scaffolds, and surgical procedures that interact mechanically with biological structures.

Computational Biomechanics

Finite-element analysis, multibody dynamics simulation, and computational fluid dynamics are applied to biological systems to predict stress distributions, joint loading, blood flow, and respiratory airflow in configurations that cannot be studied experimentally. Subject-specific models are constructed from medical imaging data, with CT or MRI scans providing the geometry and, in some cases, the local material properties of bone or soft tissue. These models are used in orthopedic implant design to predict how fixation hardware will distribute load in the surrounding bone, and in cardiovascular research to study hemodynamic forces on arterial walls. IEEE Transactions on Biomedical Engineering publishes computational biomechanics research, including the development of musculoskeletal simulation platforms and real-time models suitable for surgical navigation and rehabilitation robotics.

Applications

Biomechanics has applications in a range of fields, including:

• Orthopedic implant design and preoperative surgical planning
• Sports performance analysis and injury prevention
• Wearable robots and exoskeleton design for rehabilitation and assistance
• Ergonomics and occupational health assessment
• Crash safety testing and protective equipment design