Lecture 3 Biomechanics February 2 2015 All of the quiz question will also appear on the quiz and the test He will only give them out in class so this is the only chance you will get to see them I have written them out for you at the very end and beginning of the notes Quiz1 These cells are responsible for forming new bone a Osteoblasts 3 types of muscles o Skeletal muscle cardiac muscle smooth o Skeletal voluntary Skeletal muscle o Voluntary Cardiac muscle o Only found in heart o Involuntary o CNS controlled o Stimulated by voluntary motion Smooth muscle o Walls of hollow organs Irritability o Able to respond to stimulation o Stimulation motor neuron Most sensitive tissue in skeletal muscles So you control the force of the reaction Contractibility So they respond faster to the stimulation o Unique to muscle tissue o Tension o 50 70 shortening possible Extensibility o Like elastic material o Protect you organs from injury o It has to work with other muscles to elongate Elasticity o It can restored to its original length Functions of the skeletal muscles o Movement o Maintain temperature o Control entrance and exit through the body Groups of muscles o Muscles work together to produce movement o Fascia Elasticity Sheet of fibrous tissue Muscle architecture o Parallel vessels o Pennate run diagonally with respect to a central tendon Muscle Volume mass density Anatomical cross section o A measurement of the cross sectional area perpendicular to the longitudinal axis of the muscle Physiological cross section o A sum total of all of the cross sections of fibers in the muscle Fiber organization o o Fusiform ACS PCS These muscles look like parallel muscles Penniform 3 types o o o o o Semimembranosus Off one side of tendon Bipennate Gastrocnemius Off both sides of tendon Multipennate Deltoid Both Slow twitch Oxidative Slow contraction time low intensity work Type 2 a RED Fast twitch Oxidative glycolytic Long duration activity Burst and then fatigue Type 2 b WHITE Fast twitch Rapid force Fatigue Myofibril Contractile unit Shaped like a log Sarcomere Functional unit of skeletal muscle Sliding filament theory o Type 1 o Unipennate Explains how the actin and myosin slide to elongate the sarcomere Muscle contraction Resting potential When voltage travel across the plasma membrane while in a resting state Excitation contraction coupling Twitch Tetanus o o Sustained muscle contraction Motor unit Functional element that provided action potential to muscle Single motor unit can activate a group of muscles Some small Extraocular muscles Some large gastrocnemius Muscle Attachment 3 ways muscles attach to bone Directly Via tendon o Inelastic bundle of collagen fibers o Supporting flexibility Via a aponeurosis o Origin attachment is closer to the midline or more proximal Insertion attachment is further from the midline or more distal Tendon o Transmits force to bone o Withstands high tensile loads o Stress and strain response o Sheath of fibrous tissue Linear and non linear areas Provide more flexibility in motion Mechanic model of muscle o Muscle can store the energy and impact o Three component model Contractile CC Parallel elastic PEC Hill Muscle model o Most common more powerful o Torque o Causes the rotation of motion o Distance from axis of rotation to movement o T rF o Force should be perpendicular to the movement o Parallel force does not contribute to calculating torque o F costheta T o Movement arm is always perpendicular to the force line of action o Example o Flexion Agonist biceps o Extension Agonist triceps Isometric Tension increases no movement Isotonic o Concentric shortens to cause movement o Eccentric muscle contracts as it lengthens Triceps are being elongated Factors influencing muscle force o Angle of attachment o Force time characteristics o Force velocity relationship o Length tension relationship Stretch shortening Cycle o Bicep curls Agonist vs antagonist o It is more useful because it is a closed circuit Alternative not a closed circuit Series elastic SEC Fatigues quickly Muscle Fatigue o Results from o Muscular and nervous mechanisms When the motor unit fatigues there is a change in the frequency content and the amplitude of the EMG signal o Recovery is possible from rest Principles of training o Genetic predisposition o Training specificity o Intensity o Rest o Volume Strength training and the Nonathlete o ACM two days per week and eight twelve exercises per day o Counteracts atrophy Training modalities o Isometric o Isotonic o Same velocity varied resistance Close linked o Same weight throughout the ROM Isokinetic o Rehabilitation Isotonic one segment is fixed Variable resistive Overloads muscle For people with movement disorders Tai chi Stretching Injury to skeletal muscle o When performing tasks for first time o You can prevent it by warming up or building up slowly Quiz 1 The ability to respond to stimulation is called a Contractility b Extensibility c Irritability d Elasticity 2 The stretch shortening cycle consists of in the same muscle a An eccentric contraction followed by a concentric contraction 3 As a person stands from a sitting position what is the predominant contraction type I n the lower extremities a Concentric the quads 4 if you are sitting down after standing up it is eccentric 5 the endomysium covers the a muscle fibers 6 a functional unit of skeletal muscle is a a sarcomere 7 actin myosin cross bridge forms when a calcium ions cause active sites to be exposed 8 muscles with lots of sarcomeres in parallel can achieve high a force 9 a motor unit a one neuron and all of the muscle fibers it connects to 10 an exercise is considered as an when the segment moves a specified weight through a range of motion a isotonic 11 which scenario describes an eccentric contraction a The knee is flexing as the knee extensor muscle group