Biomechanics is the scientific study of mechanical aspects of living organisms and biological movement, applying principles from mechanics, physics, engineering, mathematics, anatomy, and physiology to biological structures and systems. It examines how forces are generated, transmitted, resisted, and transformed by tissues, organs, limbs, organisms, and biological materials. Biomechanics can address human movement, animal locomotion, musculoskeletal function, tissue mechanics, fluid interactions, injury mechanisms, prosthetic design, sports performance, rehabilitation, and biological adaptation.
The field includes statics, dynamics, kinematics, kinetics, material mechanics, fluid mechanics, and computational modelling. Unlike purely mechanical engineering, Biomechanics must account for biological tissues that can grow, remodel, heal, deform, exhibit nonlinear behaviour, and vary substantially between individuals. The interaction between structure and function is therefore central to understanding biological mechanical systems.
The historical development of Biomechanics extends from anatomical observations and early studies of animal and human movement to quantitative mechanics. Aristotle studied animal locomotion, while Leonardo da Vinci produced detailed anatomical and mechanical observations of the human body. Galileo contributed to the analysis of material strength and scaling, and later researchers developed more systematic mathematical descriptions of movement. Giovanni Alfonso Borelli applied mechanical principles to muscular action and is often associated with foundational work in biomechanics.
During the nineteenth and twentieth centuries, advances in physics, anatomy, physiology, photography, force measurement, and engineering transformed movement analysis. Modern Biomechanics uses motion capture, force plates, electromyography, medical imaging, finite element analysis, computational fluid dynamics, wearable sensors, robotics, and machine learning to investigate mechanical function across many scales.
Kinematics describes motion without necessarily considering the forces producing it. Position, displacement, velocity, acceleration, joint angles, angular velocity, and trajectories are common kinematic quantities. Kinetics examines the forces and torques associated with motion. Newton's laws of motion provide fundamental relationships between mass, acceleration, and force, while rotational mechanics relates torque, angular acceleration, and rotational inertia. Biomechanical analyses often use free body diagrams to identify external and internal forces acting on a structure. Ground reaction forces, muscle forces, gravitational forces, joint reaction forces, and external loads can interact to produce movement. Centre of mass and centre of pressure are important quantities in studies of balance, locomotion, and stability.
Muscles generate force through physiological mechanisms involving actin and myosin interactions, but the resulting movement depends on anatomy and mechanical leverage. A muscle's line of action, moment arm, attachment points, and joint configuration determine how its force contributes to joint torque. Muscles can act concentrically while shortening, eccentrically while lengthening under load, or isometrically while producing force without substantial change in length. Muscle force depends on factors including muscle length, contraction velocity, activation level, fatigue, and physiological state. Tendons transmit muscular forces and can store and release elastic energy, which is particularly important in locomotion. The musculoskeletal system therefore functions as an integrated mechanical system rather than as a simple collection of independent actuators.
Biological tissues have mechanical properties that differ from ideal engineering materials. Bone is a composite material containing mineral and organic components and has different properties depending on anatomical location, loading direction, density, and structural organisation. Tendons and ligaments are collagen rich tissues with nonlinear stress strain behaviour and time dependent characteristics. Cartilage provides load bearing and low friction functions in joints and exhibits complex viscoelastic and poroelastic behaviour.
Stress describes force distributed over an area, while strain describes deformation relative to an original dimension. Elastic deformation can be reversible, whereas plastic deformation produces permanent structural change. Biological tissues can also remodel in response to mechanical loading, meaning that mechanical conditions can influence biological structure over time.
Biomechanics is widely used to analyse human movement and performance. Motion capture systems can record the three dimensional trajectories of markers attached to a person's body, while force plates measure forces exchanged with the ground. Electromyography provides information about electrical activity associated with muscle activation. Combining these measurements can reveal how joint motion, external forces, and muscle activation interact during walking, running, jumping, lifting, and other activities. Sports biomechanics can investigate technique, equipment interaction, energy transfer, and injury risk factors. Clinical biomechanics can assess gait abnormalities, joint loading, prosthetic function, rehabilitation progress, and the mechanical consequences of surgery. Measurements must be interpreted carefully because laboratory conditions, marker placement, model assumptions, and individual anatomical variation can influence calculated quantities.
Computational Biomechanics uses mathematical and numerical models to investigate mechanical behaviour that may be difficult to measure directly. Finite element methods can estimate stress and deformation in structures such as bone, implants, joints, and soft tissues by dividing a complex geometry into many smaller elements. Multibody dynamics models represent linked rigid or deformable bodies and can simulate movement of the musculoskeletal system.
Computational fluid dynamics can examine interactions between biological structures and flowing fluids, such as blood or air during respiration and locomotion. Musculoskeletal models can estimate muscle forces and joint loads from movement and external force measurements, although these estimates depend on anatomical parameters, optimisation assumptions, and available measurements. Model validation against experimental data is essential because computational sophistication does not guarantee biological accuracy.
Biomechanics has major applications in medicine, rehabilitation, orthopaedics, prosthetics, ergonomics, sports, robotics, and product design. Implant design requires understanding how artificial materials interact mechanically with bone and surrounding tissues. Prosthetic limbs must provide appropriate mechanical function while accommodating the user's anatomy and control capabilities. Ergonomic analysis seeks to reduce excessive physical loading associated with workplace tasks and equipment. Injury biomechanics examines how impacts, forces, tissue properties, and movement patterns contribute to damage. In rehabilitation, quantitative movement analysis can help evaluate changes in function over time. Animal biomechanics can explain locomotor adaptations, feeding mechanisms, flight, swimming, jumping, and structural design across species, linking mechanical performance with evolutionary and ecological pressures.
