CLINICAL BIOMECHANICS Describe how clinical biomechanics is integrated into the greater discipline of exercise science Identify the characteristics of force. Describe several basic biomechanical principles Explain the effects of forces on biologic tissues Describe how electromyography is being incorporated into clinical practice Define the scope of ergonomics and its relationship to clinical biomechanics.
What is Clinical Biomechanics • Study of forces and their effect on living organisms. • Understanding of human movement; mechanics of injury; principles of prevention, evaluation, and treatment of musculoskeletal problems.
Applies concepts and principles that are important to the discipline of exercise science as well as other academic disciplines and professions. • Bioengineers, ergonomists human factors specialists, etc… • Research in biomechanics help understand human movement and is then applied to a clinical setting • ex: physical therapists rehabilitate injured patients, orthopedic physicians repair broken limbs or ruptured ligaments, instructs proper lifting techniques.
After prevention of injury, aiding disabled individuals live an efficient and safe life is the next main area of research. • Normal patterns of movement are studied to help answer questions of injured or disabled patters of movement. • If movement can’t be returned to normal then efficient and safe patterns must be applied.
The study of biomechanics involves both statics and dynamics. • statics- stationary • Dynamics-motion • Studies are carried out to answer questions like: • What forces act on the body durng various activities? • How does position of a body part affect the muscle force needed to maintain the body part position? • What are the differences in rehabilitating a body part with free weights, isokinetics and isoinertial devices? • Isokinetics is a term used for muscle action when the rate of shortening or lengthening of the muscle is constant • Isoinertial-term for a muscle action in which the load on the muscle is constant.
Kinesiology • Is the study of motion involving the skeletal system, joint articulations and muscle groups that are the prime movers. The major joints are: Shoulder girdle, shoulder, elbow, radioulnar, wrist, lumbrosacral, spine, hip, knee, ankle, intertarsal. Each of these have their own unique action
Abduction: movement of bone laterally away from the midline of the body. • Adduction: movement of a bone medially toward the midline of the body • Eversion: turning the foot so that the bottom of the foot is turned away from the midline of the body. • Extension: movement of a joint in which the angle between the limb segments increases • Flexion: movement of a joint in which the angle between the limb segments decreases • Hyperextension: continuation of extension posat the anatomical position • Inversion: turning the foot so that the bottom of the foot is turned toward the midline of the body. • Pronation: rotation of the wrist so that the pams turn downward • Roation: turning of a bone on its longitudinal axis • Supination: rotation of the wrist so that the palms turn upward
Force • Forces can be separated combined and manipulated • Understanding how force acts on objects and what can result when forces are applied to various materials is what clinical biomechanics is all about. Force: is a push or pull. When applied externally to an object it is called a load. F=ma Force=mass X acceleration
Characteristics of Force • Point of application: attachments of muscles to bones, center of mass of a limb, and point of contact with a dumbbell. • Line of application: force acts anywhere along a line of application but this line can be redirected by a fixed pulley. • Force has a direction: up, down, left, right, etc… • Force has a magnitude-howmuch force
Newton's Laws • Law of Inertia: an object with mass will remain at rest or maintain a constant velocity unless it is acted on by an external force. • Law of acceleration: an objects velocity changes in magnitude and or diractoin when an external force is applied. • Law of action-reaction: for every external force applied to an object and equal but opposite force is generated on the object that initiated the contact.
Gravity • Gravity is the mutual attraction between two objects. The magnitude of the force of gravity is directly proportional to the mass of each object and inversely proportional to the distance between objects. • the magnitude of the earths fgravity on an object is called its weight. • W=mg where m=mass and g=acceleration of object caused by gravity. • On earth gravity is “down” and is a straight line between an objects center of mass.
Muscle • Muscle force maintains posture and movement. • Skeletal muscles have 4 shapes. Spindle shape: inline to the direction of pull • Fan shape: in line to the direction of pull; wider than spindle shape. • Bipennate shape; at an angle to the direction of pull; fibers converge on both sides of the tendons • Unipennate shape; at an angle to the direction of pull; fibers converge on only one side of the tendons. • Muscle force occurs at the expense of the nervous system.
Muscle has four properties: excitability, conductivity, contractility, extensibility, and elasticity. • Excitability gives muscle the ability to respond to a stimulus. • Conductivity gies it the ability to propagate an electrical current. • Contractility is the ability of the muscle to shorten and generate force when stimulus is received. • Extensibility means a muscle can be stretched • Elasticity means muscle is able to return to its original resting length
Isometric contraction is when the length of the total muscle doesn’t change. Isometrics are done in static positions, rather than being dynamic through a range of motion. • Concentric contraction occurs of the muscle force exceeds the resistance offered at the muscle attachements and the distance between the attachments decreases. • Eccentric contraction occurs when the resisting force at the muscle attachments exceeds the muscle force produced by the muscle and the muscle lengthens.
Inertia • Whether an object is stationary or moving it has inertia. In order to make an object start, stop or change direction a certain sized force must be applied. Use the equation F=ma. Elasticity • Some objects can reform their original size and shape once they’ve been deformed. The magnitude of the force depends on the type of material and the amount of deformation: F=-kl • K is a constant value based on the specific type of material. • l is the amount of deformation that occurred.
Buoyancy • An upward boyant force acts on an object when the object is immersed in a fluid. The magnitude of the force is equal to the weight of the flud displaced by the object. The line of appluication is vertical and the point of application is the objects center of mass. • Pool therapy is used to reduce the force of gravity on the lower limbs. • F=W-B • Force =weight minus displaced water weight.