Biomechanics Exam 2

Chapter 5: The Biomechanics of Human Skeletal Articulations

Classification of Joints

• Synarthroses: immovable

  -only place these sutures are located is in the skull.

  -Don’t form until around the age of 1

• Synarthroses: Immovable (very slight amount of movement)

  • Syndesmoses

  • The mid-radioulnar joint is an example of a syndesmosis, where the fibrous tissue binds the bones together

• Amphiarthroses: slightly moveable

  -Synchondroses

  -The sternocostal joints are examples of synchondroses, wherein the articulating bones are joined by a thin layer of hyaline cartilage

• Amphiarthroses: (slightly moveable)

  -Symphyses

  -Note that the hyaline cartilage disc separating the bones of the pubic symphysis typical of a symphysis joint

• Diarthroses or synovial: (freely movable) is characterized by

• Articular cartilage: a protective layer of dense white connective tissue covering the articulating bone surfaces

• Articular capsule: a double-layered membrane that surrounds the joint

• Diarthroses or synovial: (freely movable) characterized by:

  • Synovial fluid - a clear, slightly yellow   liquid that provides lubrication inside   the articular capsule

  • Associated bursae - small capsules filled with synovial fluid that cushion the structures they separate

• The knee is an example of a synovial joint, with a ligamentous capsule, an articular cavity, and articular cartilage

• Gliding, hinge, pivot, condyloid, saddle, and ball and socket are all diarthroses/synovial joints

• Ball and socket = Hip, shoulder

• Condyloid Joint= knuckles

• Pivot Joint= Axis and atlas (head and neck)

• Saddle Joint= thumb

• Hinge Joint= elbow and knees

• Articular cartilage: A dense, white connective tissue, 1-5mm thick, that coats the ends of bones articulating at diarthrodial joints

  -It spreads loads over a wide area, thereby reducing contact stress

  - It provides a protective lubrication that  minimizes friction and mechanical wear at the joint

• Articular Fibrocartilage: Soft-tissue discs or menisci that intervene between articulating bones, as exemplified by the menisci of the knee above)

  •Distributes loads over joint surfaces

  • Improves the fit of articulations

  • Limits the slip between articulating bones

  • Protects the joint periphery

  • Lubricates the joint

  - Absorbs shock at the joint

Articular Connective Tissues

• Tendons: connect muscles to bone

• Ligaments: connects bones to other bones

• The insertion point is where the movement occurs whereas the origin is where it begins.

Joint Stability

• Joint Stability: the ability of a joint to resist abnormal displacement of the articulating bones, or joint displacement

  subluxation resets itself on its own, dislocations has to be reset by someone.

• Factors that increase joint stability:

  •A closely reciprocating match of the articulating bone surfaces (stability   is maximal when joints are in the close-packed position)

  • A strong array of ligaments and muscle tendons crossing the joint

  • Absence of muscle fatigue

  (ball and socket joint, saddle joint, and hinge joint are all examples of reciprocally shaped mechanical articulations)

Joint Flexibility

• Joint Flexibility: A description of the relative ranges of motion allowed at a joint in different directions

• Range of Motion: the angle through which a joint moves from   anatomical position to the extreme limit of segment motion in a   particular direction (measured directionally from anatomical position which is zero)

• Tissue Proximity: where the ROM ends

• Factors that influence joint flexibility:

  •Intervening bony or muscle tissue or fat at the end of the ROM

  • Tightness/laxity in the muscle and collagenous tissue crossing a   joint

  • Muscle fatigue

Techniques for Increasing Joint Flexibility

• Golgi tendon organs inhibit and increase tension in muscles, and initiate tension development in antagonists. These organs are located near the muscle tendon junction in series with muscle fibers. Overall promotes stretch in muscles being stretched. (stops your body from overstretching your muscles. They take 7-12 seconds to relax)

• Muscle spindles provoke reflex contraction in stretched muscle and inhibit tension in antagonists. They are interspersed among muscle fibers in parallel with the fiber and increase in muscle length.

• Active Stretching: produced by active development of tension in the   antagonist muscles (stretching yourself)

• Passive Stretching: produced by a force other than tension in the antagonist muscles (someone else is stretching you)

• Ballistic stretching - a series of quick, bouncing-type stretches (bouncing while touching toes)

• Static stretching - maintaining a slow, controlled, sustained stretch over   time (usually about 30 seconds) (touching your toes without moving)

• Proprioceptive neuromuscular facilitation (PNF) is a group of stretching procedures involving alternating contraction and relaxation of the muscles being stretched. It required the assistance of a partner.

  (think of doing a hamstring stretch on someone)

• Osteoarthritis: A common, degenerative disease of articular cartilage

  • Symptoms include pain, swelling, ROM restriction, and stiffness

  • Cause is unknown

  • Both too little and too much mechanical  stress seem to promote development

Chapter 6: The Biomechanics of Human Skeletal Muscle

• Extensibility: The ability to be stretched or to increase in length

• Elasticity: The ability to return to normal resting length following a stretch

  Components of muscle elasticity:

  • Parallel elastic component (PEC):  passive elasticity derived from muscle membranes (in the muscle belly)

  •Series elastic component (SEC):  passive elasticity derived from tendons when a tensed muscle is stretched (at the point that muscles connect to the bones) basically in the tendons

• bicep brachii has 2 heads and your tricep has 3 (bi2, tri3)

  What is the stretch-shortening cycle?

• Eccentric contraction. Occurs when the muscle is actively stretched, followed immediately by concentric contraction

• Irritability: the ability to respond to a stimuli

  •Ability to develop tension: the contractile component of muscle function

• Muscle Fiber: Single muscle cell surrounded by a membrane called the sarcolemma and containing specialized cytoplasm called sarcoplasm)

• Sarcoplasmic reticulum: holds a lot of the things we need to make a muscle contraction

• Some muscle fibers run the entire length of a muscle

• Skeletal muscle: grows from the beginning of your life to the end in both diameter and length.

• Fiber diameter can increased with resistance training.

• The sarcomere is the basic structural unit of the muscle fiber.

• Myosin is thick and actin is thin. For a contraction, the myosin head grabs onto the actin and pulls

• The alternating dark and light bands of the sarcomere give muscle its striated appearance.

• The A bands of a sarcomere contain thick, rough myosin filaments surrounded by six thin, smooth actin filaments.

• The I bands of a sarcomere contain only thin actin filaments

• Motor Unit: Single motor neuron and all fibers it innervates. It is considered the functional unit of the neuromuscular system

• Fast twitch (FT) fibers both reach peak tension and relax more quickly than slow twitch (ST) fibers.

• Fast Twitch is for short burst activities

• Type I slow-twitch oxidative fibers are muscle fibers that are highly resistant to fatigue and are primarily used for endurance activities. usually smaller and are used all day long for basic activities. They have a high density of mitochondria, myoglobin, and capillaries, allowing them to efficiently use oxygen for aerobic metabolism.

• Type IIx Fast Twitch Oxidative Glycolytic fibers are a type of fast-twitch muscle fiber that primarily rely on anaerobic metabolism for energy. They are designed for short bursts of intense activity (sprinting or lifting). They generate quick, powerful contractions but fatigue rapidly.

• Type IIa fast-twitch Glycolytic fibers, are muscle fibers that have a moderate resistance to fatigue and can generate energy through both aerobic and anaerobic metabolism. They are used for activities that require both strength and endurance, (mid distance or boxing) They provide a balance between power and stamina, making them versatile for various athletic performances.

  How are muscle fibers organized?

• Parallel Fibers: fibers are roughly parallel to the longitudinal axis of the muscle; examples include biceps femoris, biceps brachii

• Pennate Fibers: short fibers attach to one or more tendons within the muscle. found in you calf muscle(gastroenemis) and ab muscles

• Concentric, Eccentric, and Isometric are terms used to describe muscle contractions based on change in muscle length

• Concentric: muscle is shortened (a positive muscle contraction)

• Eccentric: muscle is lengthened or stretched (a negative muscle contraction)

• Isometric: No change in the length

• Isotonic: both shortening and lengthening are occuring (bicep curl)

• Isokinetic: both shortening and lengthening but the resistance stays the same.

  What roles are assumed by muscles?

• Agonist: works to cause a movement

• Antagonist: acts to slow or stop a movement

• Stabilizer: (secondary) stabilizes against the force

• Neutralizer: eliminate unwanted motion

  What disadvantages are associated with muscles that cross more than one joint?

• Active insufficiency: condition occurring when a two-joint muscle cannot shorten enough to cause full range of motion at both joints it crosses at the same time (decreased ability to form a fist with the wrist in flexion)

• Passive insufficiency: inability of a two-joint muscle to stretch enough to allow full range of motion at both joints at the same time (decreased ROM for wrist extension with the fingers extended)

• Muscular strength is measured by the amount of torque a muscle group can generate at a joint. uses weights or machines to test

• The component of muscle force that   produces torque (F_t) at the joint is directed perpendicular to the attached bone.

• Torque produced by a muscle (Tm) at the joint center of rotation is the product of muscle force (Fm) and muscle moment arm (d  ).

  What factors affect muscular strength

• Tension-generating capability of the muscle tissue, which is in turn   affected by:

  • Muscle cross-sectional area

   Training state of muscle

• moment of arms and the muscle crossing the joint (the longer the muscle takes to cross the joint,the weaker it is)

• distance

• angles

  What is muscular power?

• The product of muscular force and the velocity of muscle shortening

  What is muscular endurance?

• The ability of muscle to exert tension over time.The opposite of muscle fatigue ability

• warmups before working out are important because it excites the nerves and muscles making them more effective.

Chapter 7: The Biomechanics of the Human Upper Extremity

Structure of the Shoulder

• Sternoclavicular joint: modified ball and socket joint between the proximal clavicle and the manubrium of the sternum

• Acromioclavicular joint: irregular joint between the acromion process of the scapula and the distal clavicle

• Coracoclavicular Joint: syndesmosis with the coracoid process of the scapula bound to the inferior clavicle by the coracoclavicular ligament

• Glenohumeral joint(shoulder joint): ball and socket joint in which the head of the humerus articulates with the glenoid fossa of the scapula (fossa is a cavity)

• Scapulothoracic joint: articulation between the anterior scapula and the thoracic wall

• Rotator Cuff is composed of the supraspinatus, Infraspinatus, Teres Minor, subscapularis. (SITS)

  Movements of the Shoulder Complex

• Scapulohumeral rhythm: a regular pattern of scapular rotation that accompanies and facilitates humeral abduction

• The major flexor muscles at the glenohumeral joint are the clavicular pectoralis major and anterior deltoid, with assistance provided by the small coracobrachialis and the short head of the biceps brachii

• The major extensor muscles at the glenohumeral joint are the sternal pectoralis major, latissimus dorsi, and teres major, with assistance provided by the long head of triceps brachii and the posterior deltoid.

• The major abductor muscles at the glenohumeral joint are the middle deltoid and supraspinatus.

• The adductor muscles at the glenohumeral joint are the latissimus dorsi, teres major, and sternocostal pectoralis, with assistance provided by the short head of biceps brachii and the long head of triceps brachii ( Same as extensors)

• The medial rotator muscles of the humerus are subscapularis and teres major, assisted by pectoralis major, anterior deltoid, latissimus dorsi, and the short head of biceps brachii.

• The lateral rotator muscles of the humerus are infraspinatus and teres minor, assisted by the posterior deltoid.

• The horizontal adductor muscle muscles of the humerus are the pectoralis major anterior deltoid, and coracobrachialis, assisted by the short head of biceps brachii.

• The horizontal abductor muscles of the humerus are infraspinatus, middle and posterior deltoid, and teres minor, assisted by teres major and latissimus dorsi.

  Structure of the Elbow

• Humeroulnar Joint: Hinge joint in which the humeral trochlea articulates with the trochlear fossa of the ulna. Considered to be the elbow joint

• Humeroradial Joint: Gliding joint in which the capitellum of the humerus articulates with the proximal end of the radius.)

• Radioulnar joint: The proximal and distal radioulnar joints are pivot joints.The middle radioulnar joint is a syndesmosis.

  Movements at the Elbow

• The flexor muscles at the elbow are the brachialis, biceps brachii, and brachioradialis

• The extensor muscle at the elbow is the triceps brachii, assisted by anconeus.

• The pronator muscle of the forearm is the pronator quadratus. (pour dow is pronation, turn up is supination)

  Structure of the Wrist

• Radiocarpal Joints: Condyloid articulations between the radius and the three carpal bones. (These joints comprise the wrist.)

• What is the function of the retinacula at the wrist? (These fibrous bands of fascia form protective passageways through which tendons, nerves, and blood vessels pass.)

• The flexor muscles at the wrist are the flexor carpi radialis, flexor carpi ulnaris, and palmaris longus, assisted by flexor digitorum superficialis and flexor digitorum profundus.

• The extensor muscles at the wrist are extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris, assisted by other wrist extensor muscles.

  Structure of the Joints of the Hand

• carpometacarpal joints: Joints between the carpal bones of the wrist and the metacarpal bones of the hands.) The carpometacarpal joint of the thumb is a saddle joint. The other carpometacarpal joints are gliding joints.

• intermetacarpal joints: Irregular joints between the metacarpals and the carpometacarpals

• Metacarpophalangeal joints: Condyloid joints between the rounded distal heads of the metacarpals and the concave proximal ends of the phalanges these joints form the knuckles of the hand.

• interphalangeal joints: The proximal and distal interphalangeal joints of the fingers and the single interphalangeal joint of the thumb are all hinge joints.

  Movements of the Hand

• What motions are permitted at metacarpophalangeal joints 2-5?

  - Flexion

  -Extension

  -Abduction

  -Adduction

  -Circumduction

• Grade 1 sprain of a ligament means it is stretched

• Grade 2 sprain of a ligament means it is partially torn

• Grade 3 sprain mans the ligament is completely gone.

Chapter 8: The Biomechanics of the Human Lower Extremity

What is the Hip Joint?

• Hip Joint: A ball and socket joint where the head of the femur articulates with the concave acetabulum

• More stable than the shoulder because of bone structure and the number and strength of the muscles and ligaments crossing the joint

• The integrity of the hip is enhanced by the strong ligaments crossing the joint.

• The pelvic girdle includes the two ilia and the sacrum. It can be rotated forward, backward, and laterally to optimize positioning of the hip.

  What Movements of the femur are facilitated by pelvic tilt?

• Posterior tilt is flexion

• Anterior Tilt is Extension

• Lateral tilt is Abduction

  Movements at the Hip

• Flexor muscles at the hip are iliacus and psoas major, assisted by pectineus, rectus femoris, sartorius, and tensor fascia latae

• Extensor muscles at the hip are gluteus maximus and the hamstrings: biceps femoris, semimembranosus, and  semitendinosus.

• The abductor muscle at the hip is the gluteus medius, assisted by gluteus minimus. (ab means away)

• The adductor muscles at the hip are adductor magnus, adductor longus, and adductor brevis, assisted by gracilis.

  Structure of the Knee

• Tibiofemoral Joint: Dual condyloid articulations between the medial and lateral condyles of the tibia and the femur; composing the main hinge joint of the knee. Considered to be the knee joint

• Patellofemoral joint: Articulation between the patella and the femur (The patella improves the mechanical advantage of the knee extensors by as much as 50%)

• Menisci: Cartilaginous discs located between the tibial and femoral condyles. They distribute the load at the knee and absorb shock. Includes the medial and lateral.

• Collateral ligaments: cross the medial and lateral aspects of the knee. (MCL and LCL)

• Cruciate ligaments: cross each other in connecting the anterior and posterior aspects of the knee. (PCL and ACL)

• The hamstrings, assisted by the gracilis, sartorius, popliteus, and gastrocnemius contribute to flexion at the knee ( semimembranosis, semitendinoses, bicep femoris

• The quadriceps contribute to extension at the knee (vastus laterlis, vastus medius, rectus femoris, vastus intermedius

  Movements at the Ankle

• Tibiotalar Joint: Hinge joint where the convex surface of the superior talus articulates with the concave surface of the distal tibia. Considered to be the ankle joint (ankle joint)

• Distal Tibiofibular Joint: A syndesmosis where dense, fibrous tissue binds the distal tibia and fibula together

• Dorsiflexors at the ankle include tibialis anterior, extensor digitorum longus, and peroneus tertius, assisted by extensor hallucis longus.

• Plantar flexors at the ankle are gastrocnemius(calf) and soleus(outer calf), assisted by tibialis posterior, plantaris, peroneus  longus, flexor hallucis longus, peroneus brevis, and flexor digitorum longus. (Calcaneal tendon is achilies)

  Structure of the Foot

• Subtalar Joint: The anterior and posterior facets of the talus articulate with the sustencalculum tali on the superior calcaneus

• The tarsometatarsal and Intermetatarsal Joints

  • Nonaxial joints that permit only gliding movements

  • Enable the foot to function as a semi-rigid unit and to adapt flexibly to uneven surfaces during weight bearing

• Metatarsophalangeal and Interphalangeal joints

  • Condyloid and hinge joints, respectively

  • The toes function to smooth the weight shift to the opposite foot during walking and help maintain stability during weight bearing by pressing against the ground when necessary

• Plantar Arches: The medial and lateral longitudinal arches stretch from the calcaneus to the metatarsals and tarsals. The transverse arch is formed by the bases of the metatarsal bones

• Plantar Fascia

  •Thick bands of fascia that cover the plantar aspects of the foot

  • During weight bearing, mechanical energy is stored in the stretched ligaments, tendons, and plantar fascia of the foot. This energy is released to assist with push-off of the foot from the surface.

  What muscles are responsible for toe flexion and extension?

  •Flexion: flexor digitorum longus, flexor  digitorum brevis, quadratus plantae,   lumbricals, interossei

  • Extension: extensor hallucis longus,   extensor digitorum longus, extensor   digitorum brevis

  What muscles are responsible for inversion and eversion?  

  •Inversion - tibialis posterior, tibialis anterior

  • Eversion - peroneus longus, peroneus brevis, assisted by peroneus tertius

• concentric- shortening or contract

• ecentric- is elongation