Biomechanics: The Physics Of Human Movement

Explore the basics of mechanics within biomechanics, defining motion, forces, and the core formulas, including kinematics, dynamics, statics, and kinetics, that describe human movement.

Explore steady velocity and formula v = s/t for distance over time in meters per second. Examine circular velocity in ventilators or propellers with v = 2π r / T.

Define steady and radial acceleration as the change of velocity over time and the force-mass relationship, using a = v/t and a = f/m, with examples from sprinting and throwing.

Explore how force arises from interactions between objects, with magnitude and direction tied to mass and acceleration, including weight as gravity and radial force from velocity and radius.

Define momentum as p = m v and, independent of force, show its conservation in a closed system where momentum before equals momentum after, illustrated by the Newton pendulum.

Explore energy in biomechanics, covering kinetic energy (1/2 m v^2) and potential energy (m g h), their units joule and newton meter, and energy conservation in movement.

Define mechanical work as the energy moved or deformed by a force, dependent on force and distance, and measured in joules or newton meters as the necessary energy for movement.

Explore mechanical power as work per second and the force–velocity relationship, showing how high forces and fast muscle contraction drive athletic performance like jumping.

Analyze forces, moments, and equilibrium in the statics of the human body, focusing on external, internal, reaction forces, and weight at the center of mass during acceleration.

Discover how Newton's three laws explain forces in static systems and how equilibrium arises from equal and opposite forces, weight, and reaction forces in human movement.

Explore reaction forces and Newton's third law, where external forces balance static systems to maintain equilibrium, with examples like standing and a box pushing against a wall.

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Explore the basics of trigonometry, focusing on sine and cosine, to calculate angles and side lengths in a right triangle using a practical alpha 30 degrees, c 50 cm example.

Distribute the force into horizontal and vertical components using fx = F cos alpha and fy = -F sin alpha, illustrating static equilibrium.

Compute moments in biomechanics using m = f d, where force, distance from origin, and line of action determine the moment's magnitude and sign, with counterclockwise positive and clockwise negative.

Explore equilibrium conditions in a static two-dimensional system, deriving forces and moments balance, using a plank example to solve for reaction forces R1x, R1y, R2x, R2y from gravity.

Explore how the center of gravity shifts with body position and limb movement, as weights of body parts determine the line of action and internal muscle forces.

Explore static friction and how the surface coefficient and normal force prevent motion on an incline, applying fr = mu Fn with mu 0.6 and Fn 500 N.

Apply static analysis of the arm to calculate the biceps force in newtons and the shoulder moment using force and moment equilibrium in a simplified model.

Explore the structure and function of bones and the skeleton, including epiphysis, diaphysis, articular cartilage, marrow, and how cortical and spongy bone enable movement and protection.

Explore cortical and spongy bone, contrasting dense, stiff tissue at the shaft with light, stable spongy tissue, and review major bone types—long tubular, flat, short, irregular, and sesamoid (patella).

Understand how Wolff's law links bone adaptation to loading. Recognize how stress shielding and insufficient movement raise fracture risk.

Examine the anatomy and functioning of joints, from synarthrosis to diarthrosis, including synostosis, syndesmosis, and synchondrosis, plus the role of articular cartilage and synovial fluid.

Explore uniaxial, biaxial, and tri axial joints, including hinge and pivot actions, saddle, plane, condyloid, and ball and socket joints, with examples from elbow, wrist, shoulder, and hip.

Explore the knee joint anatomy, the largest leg joint, with two joints—the femur–tibia and femur–patella—and a modified biaxial hinge enabling flexion, extension, slight rotation, and the screw home mechanism.

The patella protects the knee joint and links the quadriceps to the knee, extending the moment arm to lower the quadriceps force needed to produce knee flexion and extension.

Explore elastostatics, analyzing how external loads induce internal stresses and deformations in bones, ligaments, tendons, and muscles within a static system, and compare them to load capacity.

Explore internal forces in elastic statics, identifying normal forces, shear forces, bending moments, and torsional moments within a beam, and how they produce normal and shear stresses.

Explore how internal forces create stress within the humerus, distinguishing normal and shear stresses from cross-sectional area. Visualize traction and pressure and apply the normal stress concept.

Explore deformation in elastic statics by linking normal and shear stresses to changes in length and angle, and apply the strain formula epsilon = delta L / L.

Hooke's law links stress and strain. Normal stress equals elastic modulus E times epsilon in MPa, while shear stress equals G times gamma, with gamma as shear deformation.

Examine how ligaments reinforce joints and limit movement, and how tendons connect muscles to bones to transfer forces, store elastic energy, and support the foot arc and aponeurosis.

The knee joint's ligaments limit motion and provide passive stability, shaping biomechanics alongside the muscles, with LCL, MCL, ACL, and PCL guiding tibia movement.

The meniscus is a knee-specific fibrocartilage that cushions the tibia and femur by distributing contact pressure and reducing high stress on incongruent joint surfaces. Lack of blood supply hinders healing.

Explore the three muscle types—smooth, cardiac (myocardium), and skeletal—and their involuntary vs voluntary control, skeletal training for strength, and their roles in movement and maintaining body temperature.

Examine how skeletal muscles attach to bones via tendons, with origin and insertion guiding movement. Explore agonist and antagonist roles, monoarticular versus polyarticular muscles, and the hierarchy to sarcomeres.

Explore the sliding filament theory and how actin and myosin form cross-bridges within the sarcomere to slide filaments and power contraction.

Examine the sarcomere's force-length relationship, showing optimal fiber length for maximal active force and velocity, with longer fibers broadening the curve and titin-driven passive force shaping total muscle output.

Explore unipennate, bipennate, multipennate, and parallel muscle architectures and how pennation angle and physiological cross-sectional area affect maximal force, shortening velocity, and the force-length relationship.

Compare deformation and contraction velocity of parallel and unipennate muscles by calculating strain from relaxed and contracted lengths. Parallel muscles shorten faster; pennate muscles offer greater cross-sectional area and force.

Explore dynamics basics, distinguishing kinematics from kinetics and examining equilibrium in dynamic systems. Classify movements - straight-line, translations, rotations, and repetitive motions - and learn to calculate velocities, accelerations, forces, work, and energy.

Examine three dynamic idealizations—mass point, mass point system, and rigid body—and identify how their degrees of freedom and bindings determine motion in two-dimensional, three-dimensional, and rotational contexts.

Explore kinematics and kinetics, distinguishing geometry of movement from the forces and masses that drive it, with examples of velocity, acceleration, impulse, energy, and gravity.

Explore how D'Alembert's principle converts a moving mass point into a static equilibrium using virtual forces, enabling calculation of horizontal and vertical accelerations in a dynamic system.

Explore motion tracking and human motion analysis to optimize movement through activity recognition, body-part tracking, and joint-angle analysis, improving performance, reducing energy expenditure, and injury risk.

Explore the finite element method (FEM) for elastostatic analysis in biomechanics, modeling load, stress, and deformation in the spinal disc, using segmentation, nodes, and various 1D–3D elements.

Explore the inertial measurement unit (IMU) as a portable, affordable tool for motion analysis in rehabilitation and sports, using accelerometers, gyroscopes and magnetometers to measure accelerations, angular velocities, and orientation.

Examine how force plates measure ground reaction forces and moments to assess athletic power and vertical jump, while pressure plates map plantar pressures to tailor insoles for foot structure.

Explore two dimensional motion analysis, a cheap camera method that tracks sagittal plane movements after calibration to align with plane, plotting hip, knee, and ankle angles with basketball and cycling.

Compare three-dimensional motion analysis methods, from marker-based systems—the gold standard for joint kinematics with reflective markers and cameras—to markerless approaches using synchronized cameras and machine learning for field athletic analysis.

Explore data analysis in biomechanics using machine learning to interpret 2D/3D motion data from wearables and IMUs, enabling real-time feedback and bridging coaches and data scientists for performance optimization.

The instructor shares a personal passion for biomechanics and motion analysis, highlighting how movement data can prevent injuries and transform orthopedics, rehabilitation, and prosthesis design.