OT 204: Kinesiology PDF

OT 204: KINESIOLOGY ○ Anthropology: The study of humans, their societies, TOPIC OUTLINE: Basic Concepts in Kinesiology: cultures, a...

OT 204: KINESIOLOGY ○ Anthropology: The study of humans, their societies, TOPIC OUTLINE: Basic Concepts in Kinesiology: cultures, and development KINEMATICS over time, encompassing both Mechanical Principles: KINETICS biological and social aspects The Movement Systems ○ Physics: the science that Muscle Activity and Strength studies matter, energy, and the fundamental forces of nature, exploring how they interact BASIC CONCEPTS IN KINESIOLOGY: and govern the universe KINEMATICS KINESIOLOGY: combination of art & science; appreciation of beauty of human movement + understanding of BRIEF HISTORY scientific principles that provide movement CLINICAL KINESIOLOGY: application of kinesiology to environments of the health care professional ○ PURPOSE: To understand the movement & the forces acting on the human body learn how KINESIOLOGY to manipulate these forces to study of human motion = art + science prevent injury, restore function, theories and principles from anatomy, and provide optimal human physiology, anthropology, physics, performance mechanics, and biomechanics ○ Biomechanics: The KINES: STUDY OF HUMAN MOVEMENT application of the principles of mechanics to the living human Kinetics: forces body Kinematics: motion (types, direction, ○ Anatomy: The study of the quantity) structure and organization of ○ Osteokinematics: movements living organisms, focusing on of bony partners/segments the physical makeup of their that make up a joint; flexion, bodies extension, abduction, ○ Physiology: The study of the adduction functions and processes of ○ Arthrokinematics: small living organisms and their movements occuring within parts, explaining how the the joint & between joint body's systems work. surfaces; gliding, rolling, ○ Mechanics: The branch of spinning physics that deals with the behaviour of physical bodies when subjected to forces or PLANES OF MOTION: CARDINAL displacements, and the effects PLANES of these on their motion. OT 2 (AY 2024 - 2025)  Three primary planes that divide the typically by naming the proximal bone body and guide its movements first flat, two-dimensional surfaces along ○ eg: RU, AA, SI joints which movement occurs help describe how an object moves in relation to its orientation SPECIAL CASES Thumb Normal position is rotated 90° from the plane of the hand Motions of flexion and extension AXES OF MOTION occur in the frontal plane rather than the sagittal plane An imaginary line around which the Abduction and adduction occur in the body or its segments rotate during sagittal plane rather than the frontal plane movement Axes around which movement occurs Perpendicular to the planes of motion NAMING MOVEMENTS AT JOINTS Forearm: Pron & Sup As the forearm rotates, the motion no We name joints by using the names of longer occurs on a longitudinal axis but on an anterior-posterior axis the two bones that form the joint, OT 2 (AY 2024-2025) Hip: Med & Lat Rotation As the flexed hip rotates, the motion no longer occurs on a longitudinal axis but on an anterior-posterior axis TYPES OF MOTION The body and its segments move one of two ways: motion is either translatory or rotary DEGREES OF FREEDOM Number of planes within which a joint moves Given that the body and its segments move in three planes of motion, the degrees of freedom are maximal at three degrees as well. ○ maximal degrees of freedom = maximum number of different ways a body part can move Linear + Rotatory movements = FUNCTIONAL MOTION 1. UNIaxial Translatory a. joints that move in one plane ○ a.k.a. Linear around one axis ○ Motion that occurs along or b. 2 types: parallel to an axis i. Hinge ○ Rectilinear ii. Pivot movement in a straight 2. BIaxial line a. joints that move in two planes ○ Curvilinear around two axes movement in a curved b. 3 types: path i. Condyloid Rotatory ii. Ellipsoidal ○ a.k.a. Angular iii. Saddle ○ Motion occurs in a circle 3. TRIaxial around an axis or a pivot point, a. Joints that move in three so every point on the object planes around three axes attached to the axis follows the b. Ball-and-socket joints arc of a circle ○ Axis of rotation pivot point for this angular or rotary motion OT 2 (AY 2024-2025)  and C2) is a pivot joint. It allows for UNIAXIAL BIAXIAL TRIAXIAL rotation of the head from side to side, Hinge Joints Condyloid Ball-and-Soc such as when shaking the head "no." convex & Joints ket Joints concave “condyloi e.g. hip & CONDYLOID AND ELLIPSOID JOINTS surfaces d”=“condy GH (SH) e.g. le” jt elbow, IP, spherical and knee convex + jts concave e.g. MCP jt Pivot Joints Ellipsoid cylindrical Joints or conical spindle-lik e.g. RU & e The terms are often used AA jts flattened interchangeably because ellipsoid convex + joints are essentially a subtype of deep condyloid joints with a more specific concave shape. e.g. AO jt Condyloid joints: oval-shaped Saddle condyle + elliptical cavity of another Joints bone convex & Ellipsoid Joints: ovoid condyle concave (more elongated) that fits into an surfaces elliptical cavity perpendic ular to each SADDLE JOINTS other e.g. thumb CMC jt HINGE JOINTS Hinge joints allow movement primarily in one plane, like a door hinge, permitting only flexion and extension. The elbow joint is a hinge joint formed by the articulation of the humerus (upper arm bone) with the ulna and radius (forearm bones). It allows for Saddle joints are similar to condyloid movements like flexion and extension joints but have a greater range of of the arm. motion. They allow for flexion, extension, abduction, adduction, and PIVOT JOINTS circumduction. Pivot joints, also known as rotary The carpometacarpal joint of the joints, are a type of synovial joint in thumb is a saddle joint, where the the human body that allow rotational trapezium bone of the wrist articulates movement around a central axis. with the first metacarpal bone of the The atlantoaxial joint between the first and second cervical vertebrae (C1 OT 2 (AY 2024-2025)  thumb. This joint allows for various Joint Structure and Function movements. Anatomical and physiological aspects of how joints are built and how they BALL-AND-SOCKET JOINTS operate to facilitate movement and stability in the body Synarthrodial Amphiarthrodial Diarthrodial Fibrous Cartilaginous Synovial 1. Sutures 1. Primary 1. Hinge 2. Gomph 2. Secondary 2. Pivot osis 3. Ellipsoid 3. Syndes 4. Condyloid mosis 5. Saddle 6. Ball-and- Socket Ball-and-socket joints consist of a spherical head of one bone fitting into a cup-like depression of another bone. The shoulder joint is a classic example of a ball-and- socket joint; the head of the humerus forms the "ball" part of the joint, while the shallow, cup-shaped glenoid cavity of the scapula serves as the "socket." CIRCUMDUCTION VS ROTATION CIRCUMDUCTION ROTATION Circular or conical Turn your turning or movement of a body spinning around a part, often involving central point or axis, the sequential without changing combination of the position of the SYNARTHRODIAL JOINTS flexion, extension, joint itself from side syn comes from Greek meaning abduction, and to side. “together” or “joined” adduction. Type: I. Synarthrosis Syndesmosis Structure/Shape: Fibrous Primary Function: Stability, shock absorption and force transmission Motion: Very slight Function: Tibiofibular Articulation Types of Synarthrodial Joints SUTURES SYNDESMOSIS GOMPHOSES Edges of the Connected by Specialized bones are a ligament or a joints where a OT 2 (AY 2024-2025) interlocked membrane peg-like and bound structure fits together by into a socket a layer of connective tissue Types 1. Primary No Very slight No movement movement movement attachment of a. Immovable As a person the teeth to b. E.g. growth plates, 1st SC joint ages, the alveolar sutures may sockets in the gradually jaw ossify and become fused Found only Interosseous Dento-alveola in the skull; membrane; r joint connect the FA, tibia, fibula Connection is various maintained by bones of the a periodontal 2. Secondary cranium ligament, a. Limited movement which holds b. E.g. pubic symphysis, IV joints the tooth in place DIARTHRODIAL JOINTS di meaning “twice, double or two” Provides almost all of our joint mobility Key structural component: (+) joint cavity ○ Connects the distal end of one joint segment to the proximal end of the other joint segment ○ Maintains a small amount of fluid, called synovial fluid, within the joint space AMPHIARTHRODIAL JOINTS Amphi comes from Greek meaning “on both sides” or “around” Combinations of both fibrous and hyaline (or articular) cartilage and typically have a disc between the bony parts Type: II. Amphiarthrosis Structure: Cartilaginous Primary Function: Stability with specific and limited mobility Motion: Limited Joint Capsule Example: Pubic Symphysis Cartilage, ligaments, articular discs, intervertebral joints 1st sternocostal the joint capsule, synovial fluid, and joint bursae OT 2 (AY 2024-2025) TYPES OF CARTILAGE Fibrous ○ Dense with thick bundles of collagen fibers Joint Surfaces ○ IV discs, menisci, pubic The surface of these synovial joints symphysis are not purely geometric with flat, ○ Main role: absorb cylindrical, conic, or spherical designs shock and reduce All joint surfaces are described as friction between bones either: Hyaline/Articular ○ Ovoid (egg-shaped) ○ MC type Most synovial joints ○ Smooth, glassy The radius of the appearance due to its curvature varies from fine collagen fibers and point to point high water content Convex-concave ○ Ends of long bones, relationship ribs to sternum ○ Sellar (saddle) ○ Main role: provides a slippery surface for Types of Basic Motion joint movement; Rolling/Rocking reduces friction in ○ A rotary, or angular, joints, supports and motion in which each reinforces various subsequent point on structures one surface contacts a Elastic new point on the other ○ High density of elastic surface fibers in addition to Sliding/Gliding collagen ○ A translatory or linear ○ External ear (auricle), motion in which the the epiglottis (part of movement of one joint the larynx) surface is parallel to ○ Main role: provide the plane of the structural support with adjoining joint surface flexibility, enabling Spinning structures to bend and ○ A rotary, or angular, return to their original motion in which one shape point of contact on each surface remains OT 2 (AY 2024-2025)  in constant contact with a fixed location on the other surface Types of End-Feels Convex-Concave Relationship Sensations experienced at the end of Convex: surface that bulges outwards a joint’s ROM when it is passively Concave: surface that curves inward stretched Resistance to further motion Normal End Feels End-Feel Description Example Soft Soft tissue Knee flexion approximatio (contact n between soft tissue of posterior leg and GONIOMETRY posterior Gr. gonia, angle, and metron, measure thigh) It is a valuable clinical measurement Firm Muscular Hip flexion stretch with the used to define the quantity of joint knee straight motion, either actively or passively. (passive Because of individual variations in elastic build and body type, it is useful to use tension of the standardized ROM values as a hamstring reference, but it is most important to muscle) use the individual’s own “normal” for Capsular Extension of reliable comparison by measuring the Stretch metacarpop uninvolved, or contralateral, extremity halangeal segment, assuming that it is present joints of and unimpaired fingers (Tension in the anterior capsule) Ligamentous Forearm OT 2 (AY 2024-2025)  stretch supination sooner or acia (tension in later in the Osteoarthrist the palmar ROM than is is radioulnar usual or in a Loose ligament of joint that bodies in the inferior normally has joint radioulnar a soft or firm Myositis joint, end-feel. A ossificans interosseous bony grating Fracture membrane, or bony oblique cord) block is felt Hard Bone Elbow Empty No real Acute joint contacting extension end-feel inflammation bone (contact because Bursitis between the pain Abscess olecranon prevents Fracture process of reaching end Psychogenic the ulna and of ROM. No disorder the resistance is olecranon felt except fossa of the for patient’s humerus) protectice muscle splinting or Abnormal/Pathological End Feels muscle Occur either at a different place in the spasm range of motion than expected or have an end feel that is not Kinematic Chains characteristic of the joint Series of sequentially connected End-Feel Description Example joints and links (bones or segments) that work together to produce Soft Occurs Soft tissue movement in the body sooner or edema later in the Synovitis Open ROM than is one end of the chain is fixed, allowing usual or in a for movement at one end without joint that directly affecting the position of the normally has other end a firm or the distal segment of the chain hard moves in space end-feel. Feels boggy. Closed both ends of the chain are fixed or Firm Occurs Increased connected to a stationary point, which sooner or muscular means that movement at one end of later in the tonus the chain affects the entire chain ROM than is Capsular, the distal segment is fixed, and usual or in a muscular, joint that ligamentous, proximal parts move in relation normally has and fascial a soft or shortening Closed & Open-Packed Positions hard Describes the different ways in which end-feel a joint can be positioned, affecting how the bones and surrounding Hard Occurs Chondromal structures interact with each other OT 2 (AY 2024-2025)  Open Closed Other loose-packe N/A name/s d , resting Joint Minimal Maximal Surface Contact Capsule & Relaxed Tight Ligament Tension Mobility ↑ROM, ↓ ROM, ↓stability ↑ stability OT 2 (AY 2024-2025)  MECHANICAL PRINCIPLES: KINETICS RATE OF MOTION Velocity – speed of motion (m/s) Motion – displacement of a body or one of its Acceleration – change in velocity over segments from one point to another time (m/s2) TYPES OF MOTION CLINICAL RELEVANCE Understanding the determinants of motion is Translatory – linear movement crucial for: Rotary – angular movements around Assessing Mobility an axis ○ Evaluating joint range and motion types in patients LOCATION OF MOTION Planning Rehabilitation ○ Tailoring exercises that improve Transverse specific types of motion Sagittal Preventing Injuries Frontal ○ Identifying abnormal motion patterns MAGNITUDE OF MOTION FORCES Degrees – rotary (angle) Meter - linear ★ Produce, Stop, or modify motion ○ Gravity: the force that pulls objects towards the earth, DIRECTION OF MOTION commonly referred to as weight Based on the axes ○ Muscle forces: generated by muscle contractions ○ Externally applied resistance: forces applied from external sources like weights, resistance bands, or manual resistance ○ Friction ➔ FORCE CHARACTERISTICS ◆ Magnitude – amount of force applied, measured In Newtons or pounds MOVEMENT POSITIVE NEGATIVE ◆ Direction – line of action of the force, which influences the X-axis Right Left resulting the motion Y-axis Upward Downward NEWTON’S LAW OF MOTION Z-axis Forward Backward 1st Law: Inertia – if a body is at rest, it will remain at rest, and if a body OT 2 (AY 2024-2025)  ○ Important in understanding how to initiate motion in CLASSES OF LEVERS patients with limited mobility 2nd Law: Acceleration – states that the 1st class - Ex. Head and seesaw, neck acceleration of a body is directly muscles balancing the head proportional to the force applied and 2nd class – Ex. Wheelbarrow, standing inversely proportional to its mass on tiptoe ○ Formula: F = m x a 3rd class – Ex. Bicep curl (elbow joint ○ Helps in understanding the as fulcrum, biceps apply force, weight force needed to move body in hand is the load) parts in exercises ➔ MECHANICAL ADVANTAGE OF rd 3 Law: Action-Reaction – for every LEVERS action force there is an equal and Efficiency of a lever system in moving opposite reaction a load ○ Used in gait analysis and MA = force arm length / resistance improving balance in patients arm length Examples: CLINICAL APPLICATION ○ 1st class – balancing force and Gravity load (seesaw), balancing ○ Plays a critical role in exercises weight-bearing exercises and ○ 2nd class – force advantage activities (calf raise) Muscle forces ○ 3rd class – speed advantage ○ Responsible for stabilizing and (most limb movements) moving joints Friction ➔ CLINICAL RELEVANCE OF LEVERS ○ Essential for stability in Impact on exercise design standing and walking ○ Lever systems influence the Externally applied forces intensity and difficulty of ○ Used to enhance or resist exercises movements in therapeutic Ex. Modifying the exercises position of resistance in side leg raises changes the LEVERS mechanical advantage and difficulty A rigid bar that rotates around a fixed point called the fulcrum or axis ➔ LEVER SYSTEMS IN REHAB 1st Class Levers - useful in balancing COMPONENTS exercises, important for patients with Axis or fulcrum – pivot point (e.g. postural instability joints) 2nd Class - emphasizes strength in Force (effort) – the applied force (e.g. the calf muscles, useful in gait training muscle contraction) 3rd Class - focus on speed and range Resistance (load) – the weight or of motion, important in upper limb force to be moved (e.g. limb or rehabilitation external weight) OT 2 (AY 2024-2025)  ➔ APPLYING TORQUE IN CLINICAL SETTINGS TORQUE Manual Muscle Testing - Rotational force that acts around an ○ Example: Applying resistance axis at the wrist rather than the - F x d (where F is force applied and d forearm during elbow flexion is the distance from the axis) increases the torque required, providing a better assessment IN THE HUMAN BODY of muscle strength. Arm Movement: Therapeutic Exercises ○ When you lift something heavy ○ Example: Increasing the with your hand, your elbow challenge by extending the acts as the axis (hinge), and moment arm, such as holding the force is generated by your a weight farther from the body. muscles. The farther the weight is from your ➔ FORCE APPLICATIONS TO THE elbow, the more torque your muscles BODY need to generate to lift it. Joint reaction forces – exerted by the That’s why it’s harder to lift heavy joint surfaces in response to muscle objects when your arm is fully and external forces extended than when it’s close to your ◆ The compressive at the knee body. joint during a squat Kicking a Ball: When you kick a ball, External Forces - such as weights, your hip joint is the axis, and your leg resistance bands, and environmental acts like a lever. factors ○ The farther down your leg ○ The effect of gravity on a limb (closer to your foot), the more during a shoulder abduction torque is generated, which is why a strong kick with your foot can send the ball flying far. FREE BODY DIAGRAMS ➔ IMPORTANCE IN MOTION A graphical representation of all Torque is critical in joint movements forces acting on a body or segment where force is applied ○ Example: The torque Components: generated by the quadriceps 1. Force vectors – arrows representing muscle at the knee joint during forces, with length proportional to a leg extension. magnitude and direction 2. Application – used to analyze the ➔ FACTORS INFLUENCING TORQUE specific joint motion Moment arm length – the longer the moment arm, the greater the torque Force application angle – torque is maximized when the force is applied at 90 degrees to the lever arm ○ Torque is greater when the arm is perpendicular during a lateral raise OT 2 (AY 2024-2025)  on a patient’s knee joint during rehabilitation. Answer: Shorten the resistance arm to decrease torque and reduce joint stress. ➔ PRACTICAL APPLICATIONS Applying Mechanical Principles: Always consider lever systems, torque, and force application in exercise design. Tailoring to Patient Needs: Adjust exercises based on individual patient’s strength, mobility, and injury status. Ensuring Safety: Minimize excessive torque and forces to prevent overloading joints, particularly in patients with weakened structures or ongoing rehabilitation. CLINICAL APPLICATIONS OF CONCEPTS A. Guiding Clinical Decisions Understanding mechanical principles helps clinicians make informed decisions regarding patient treatment and exercise prescription. B. Impact on Rehabilitation Ex: Adjusting exercise parameters based on lever arms, torque, and force application to maximize therapeutic outcomes and minimize injury risk. CASE STUDIES A. CASE 1 Scenario: You want to make a quadriceps strengthening exercise more challenging for a patient without adding additional weight. Solution: Increase the length of the resistance arm. B. CASE 2 Scenario: You need to modify an exercise to reduce stress OT 2 (AY 2024-2025)  Neurons MOVEMENT SYSTEM PHYSIOLOGY OF EXCITABLE TISSUE: NERVE AND MUSCLE Nervous and Muscluar Tissue Membranes are excitable ○ Sensitive to electrochemical change ○ Able to transmit electrochemical information to produce movement Cell Membrane Difference in electrical potential Imbalance of ions from one side of the membrane to another called potential difference ○ 2 Factors: Selective Permeability Actively move ions NERVOUS SYSTEM ANATOMY ○ Resting Potential: when no OVERVIEW action is occurring and when the under resting conditions Nervous System Classification Charge is negative ○ Nerve, muscle, and sensory receptors/cells need to maintain a resting potential of -60 to -90 mV (average = -85mV) Nerve Fibers Efferent vs. Afferent Neurons List down the types of peripheral nerves (murag answeranan ni) MUSCULAR SYSTEM Muscle Fibers Action Potential Nerve Impulse: An action potential transmitted over a nerve fiber Muscle impulse: An Action potential transmitted over a muscle fiber OT 2 (AY 2024-2025)  ○ If the motor unit’s nerve activates its muscle fibers to contract, those fibers will contract maximally Gradiation of Strength of Muscle Contraction Size Principle ○ The smallest motor units are activated first Recruitment Principles ○ Increasing the number of Motor Unit motor units activated Motor neurons are located in either simultaneously increases the the brainstem or spinal cord overall muscle tension ○ Muscles of the face and head Excitatory Input/Rate Coding Principle ○ Muscles of the neck, trunk, ○ Increasing the frequency of and extremities stimulation of individual motor units increases the percentage of time that each active muslce fiber develops max tension JOINT, TENDON, AND MUSCLE RECEPTORS Joint Receptors Most of the receptors emit several action potentials per second as a ‘resting” output ○ So the body always has a Motor neurons in the spinal cord are sense of position in space located in the gray matter of the The receptor is stimulated when it is ventral/anterior horns deformed The number of muscle fibers Receptors typically adapt innervated by asinlge motor nerve fiber varies Golgi Tendon Organs ○ The more control required of a Lie within muscle tendons near the muscle, the fewer muscle fiber point of their attachment to the muscle to nerve fiber ratio a muscle ○ Detect force/tension but not has. changes in luscle length ○ The muscles that produce Average of 10-15 muscle fibers is large forces have much larger usually connected in direct line with ratios of muscle fibers to nerve each GTO fibers Autogenic Inhibition In a motor unit, all muscle fibers act as one unit, contracting or relaxing Muscle Spindles nearly simultaneously Detect changes in muscle length Principle: All-or-none law 2 functions: OT 2 (AY 2024-2025)  ○ Sensory ○ Motor Stretch Reflex The constant volley of regulatory input to the muscle spindle intrafusal fiberssets up acontant state of readiness so that although the muscle si not activated, it is literally on a Integration of Motor Control to Produce steadt state of alert, readt to act when Funcitonal Movement needed. Musculoskeletal System+Nervous ○ Constant state of readiness: System+Cognition = effective motor Muscle Tone**Postural Tone control The more often a motor pattern is Kinesthesia and Position Sense learned, the less input from the Consciously aware of the position of cortical level is required the various parts of his or her body Motor learning is concerned with how relative to all other parts and whether motor skills are acquired and how a particular part is moving or still they are made proficient, transferred, ○ Dynamic motion: Kinesthesia and retained to allow consistent, ○ Static Motion: Position sense accurate, and automatic motion. Proprioception More inclusive term Use of sensory input from receptors in muscle spindles, tendons, and joints to discriminate joint position and movement MOTOR CONTROL Movement Movement and posture are exceedingly intricate and complex. Motor Control ○ Regulation of posture and movment Muscle Synergy ○ Functional coordinated muscle activation The systems are not arranged in a hierarchy but rather in a functioning heterarchy Movement can be expressed from among a wide variety of movement combinations Different Centers/Regions OT 2 (AY 2024-2025)  movements) also referred to as “negative work” (external MUSCLE ACTIVITY AND STRENGTH force makes a joint movement and the muscle controls that TYPE OF MUSCLE FIBERS AND movement. Example “gravity”) SIGNIFICANCE IN MUSCLE FUNCTION Isokinetic ○ No change in the rate of movement) MUSCLE ANATOMIC ACTIVITY Although knowledge of the anatomic attachments and actions is essential to the study of kinesiology, it is important to recognize that these TYPE I MUSCLE TYPE II MUSCLE factors can predict muscle function FIBERS FIBERS when all of the following conditions are present: Postural Muscles- Mobility Muscles or 1. The proximal attachment is Muscles that work Non-postural against gravity as we Muscles- stabilized; sit or stand muscles that are used 2. The distal attachment moves for rapid movement toward the proximal during explosive attachment (concentric activities. contraction); -fibers that resist These movement 3. The distal segment moves fatigue and are able muscles produce force against gravity or a resistance; to maintain sustained and power rapidly but and activity. have low endurance; therefore, they cannot 4. The muscle acts alone. sustain activity for Unfortunately, these circumstances prolonged periods. rarely occur in normal function. -soleus, peroneals, These muscles include Once you know insertions and actions quadriceps, gluteals, the gastrocnemius, of muscles, you can recall other rectus abdominis, hamstrings, and upper factors that affect functional upper extremity extremity flexors. application of muscle activity. extensors, erector For example, if the proximal biceps spinae group, and short cervical flexors. brachii attachment is stabilized, the elbow will flex when the muscle activates; however, when any muscle MUSCLE ACTIVATION contracts, it shortens at both ends, so if neither end of the biceps is Isometric stabilized, the shoulder flexes and the ○ No change in muscle size elbow flexes when the biceps Isotonic Contractions: contracts. ○ Concentric (Shortening of the We can take this notion in another muscle- proximal and distal direction to better understand muscle segments moves closer) also function in a closed chain activity: If referred to as “positive work” the distal segment of a muscle’s ○ Eccentric (Lengthening of the attachment is stabilized, then the muscle during activation- usually during deceleration OT 2 (AY 2024-2025)  proximal segment is the moving end to produce greater shortening of the muscle. distance but less force. Pennate fascicles, on the other hand, MUSCLE FUNCTIONAL ACTIVITY attach at oblique angles to a central tendon. There are different pennate Agonist designs of muscles, depending upon ○ Primary Mover Muscle- the the number of fiber arrangements one that contracts to make the within a muscle. movement Unipennate muscles have one parallel Antagonist fiber arrangement whereas bipennate ○ Opposite muscle or muscle muscles have two groups of parallel group that passively elongates fibers running to one central tendon. in a relax state to allow Most muscles in the body are movement produced by the multipennate muscles with more than agonist muscle two pennate groups attaching to more Synergist than one centralizing tendon. ○ Muscle or muscles that Pennate fascicles are shorter than contracts together with the fusiform fascicles; they produce agonist muscle greater forces to the sacrifice of speed since their total cross section is MUSCLE STRENGTH larger. Since muscle strength is proportional Muscle Size to the total cross-sectional area of the Muscle fiber structure muscle, strength of pennate muscles Length-Tension Relationship is related to the combined Moment Arm cross-sectional size of the pennate Speed of Contraction muscle. Therefore, total strength of Active Tension pennate muscles is the sum of the Age and Gender cross-sectional areas of each pennate. MUSCLE SIZE LENGTH-TENSION RELATIONSHIP Muscle fibers that are long and provides majority of the joint Resting Length movement it produces while shorter ○ Position of the muscle in which muscles provide the stability of the there is no tension within the joint movement. muscle. ○ Hypertrophy: increase in Passive Tension muscle size usually due to ○ Created mostly by elongation exercise. of muscle tissues and the ○ Atrophy: decrease in muscle connective tissue called size) due to inactivity. “Fascia”. Active Tension MUSCLE FIBER STRUCTURE ○ Force produced by a muscle. In fusiform muscles, the fascicles are Active tension in a muscle is parallel and long throughout the created by activation of the muscle. cross bridges between the ○ The sartorius is an example of actin and myosin elements a strap, or fusiform, muscle. within muscle fibers. These muscles are designed OT 2 (AY 2024-2025)  SPEED OF CONTRACTION As the speed of a concentric contraction becomes slower, the muscle’s force development increases. When there is no motion, this is a maximum isometric contraction, or zero-velocity, contraction. A muscle’s decreased ability to produce a contraction force with increasing speed of shortening is based of the number of links between the actin and myosin filaments that can be formed per unit of time. The maximum number of crossbridges that can be formed occurs at slow speeds. The more rapidly the actin and myosin filaments MOMENT ARM slide past each other, the smaller is the number of links that are formed The moment arm of a muscle is the between the filaments in a unit of time lever arm that produces rotation so less force is developed. around a joint. HOWEVER, this is opposite during The muscle’s moment arm is the eccentric contraction. muscle strength length of a perpendicular line from the actually increases as speed increases joint’s axis of motion to the muscle’s during eccentric contraction until the force vector or line of pull. speed reaches a point at which the You may recall from previously muscle is unable to control the load. presented information that all of the muscle’s force rotates the joint (produces torque) when the muscle is aligned perpendicularly to the long axis of the body segment. Torque is the measure of the force that can cause an object to rotate about an axis. OT 2 (AY 2024-2025)  Males are generally stronger than females. In both genders, however, muscle strength increases from birth through adolescence, peaking between the ages of 20 and 30 years, and gradually declining after 30 years of age. After puberty, however, the muscle mass of males becomes as much as 50% greater than that of females, and the ratio of lean body mass to whole body mass also becomes greater. On the other hand, muscle strength per cross-sectional area of muscle is similar in males and females. But of course, muscle strength varies in each individual due to other factors (genetics, lifestyle, rate of biologic maturation, etc.) STRESS-STRAIN CURVE Stress is a force or load that the body or its parts resist. How well those structures are able to resist stress is dependent upon their ability to deform. This is a strain of a ACTIVE TENSION structure: the amount of deformation it The force produced by a muscle. is able to tolerate before it succumbs Active tension in a muscle is created to the stress. (factors that affect strain: by activation of the cross bridges Viscosity, Elasticity, and Extensibility) between the actin and myosin ○ Viscosity is the resistance to elements within muscle fibers. an external force that causes a Motor units are recruited in an order permanent deformation. according to the size of the motor unit ○ Extensibility is the ability to (smaller ones are recruited first), the stretch, elongate, or expand. size of the muscle cells (smaller ones ○ Elasticity is the ability to are recruited before larger ones), and succumb to an elongating the type and speed of conduction of force and then return to the muscle fibers (slower type I are normal length when the force recruited before faster type II). The is released. smaller motor units are slower to All structures, natural and man-made, respond but last longer than the larger have their specific relationship ones which respond quickly with between stress and strain. This is strong bursts. Therefore, type I motor called the stress-strain curve or units are recruited for posture. stress-strain principle. The initial section of the stress-strain AGE AND GENDER curve is the toe region. In a resting state, tissue has a crimped or wavy OT 2 (AY 2024-2025)  appearance. When stress is applied to the tissue, this slack is taken up within the toe region of the stress-strain curve. Once the tissue is elongated to the point at which the slack is taken out of the structure so it becomes taut, the stress force moves the tissue into the elastic range. This elastic range is the point at which the tissue’s elastic properties are stressed. The tissue strain and the amount of stretch move through a linear relationship when there is a direct relationship between the amount of stress applied to the tissue and the tissue’s ability to stretch. If the force or load is released at any time during either of these two ranges, the tissue returns to its normal length. On the other hand, if the force applied continues to increase, the tissue Videos of Injuries as an example of the moves from its elastic range into its stress-strain curve plastic range. In this range, there is microscopic damage to the structure; https://www.youtube.com/watch?v=HZ some of the tissue ruptures because it 2957l4r4U is unable to withstand this amount of https://www.youtube.com/shorts/qxIab stress. It is at this point that 6Ln7jw permanent change in the tissue’s length occurs. If the force is released OTHER MECHANICAL FACTORS THAT at this point, the tissue is elongated AFFECT MUSCLE STRENGTH compared to what it was prior to the stress application. Passive Excursion If the amount of stress continues to Active Excursion increase past the plastic range, the Leverage and Length-Tension tissue moves into the necking range. Interactions At this point, more and more Open Kinematic/kinetic Chain (OKC) microscopic ruptures occur until the vs Close Kinematic/kinetic Chain tissue becomes macroscopically (CKC) damaged. It is at this time that the force or load required to create tissue PASSIVE EXCURSION damage is less than previously because the tissue is weakening. The functional excursion of a muscle If the stress increase continues, is the distance to which the muscle is immediately before the tissue ruptures capable of shortening after it has entirely, a give in the structure is felt been elongated as far as the joint(s) and then the tissue rips apart, moving over which it passes allows. into the failure range. The continuity Passive excursion or passive of the tissue is lost when tissue failure insufficiency: When muscles occurs. become elongated over two or more joints simultaneously, they may reach OT 2 (AY 2024-2025)  the state of passive insufficiency. This full elongation of a muscle prevents further shortening by its opposite muscle. ○ Passive tension of muscles that cross two or more joints may produce passive movements of those joints. This effect is called tenodesis action of muscle. Active Excursion or active insufficiency: Active insufficiency occurs in multijoint muscles when the muscle is at its shortest length when its ability to produce physiologic force is minimal. LEVERAGE AND LENGTH-TENSION INTERACTIONS Another unique way the body avoids the weakness caused by active insufficiency is by changes in the mechanical leverage that occurs throughout the joint’s range of motion. OPEN KINEMATIC/KINETIC CHAIN (OKC) In the example of the biceps brachii vs CLOSE KINEMATIC/KINETIC CHAIN muscle (Fig.4.17), the physiologic (CKC) length-tension factor is most favorable when the elbow is in full extension, A common specification for a closed and the maximum tension that can be kinetic chain condition is that it is produced during muscle contraction essentially weight-bearing. In decreases as the elbow approaches contrast, an open kinetic chain and passes 90º of flexion. To condition is a non-weight bearing compensate for this loss in position. physiologic muscle tension, the Although both open and closed chain muscle’s leverage (moment arm conditions occur in functional upper length) increases to its maximum at and lower extremity activities, the 90º. This increase in moment arm upper extremity is more often used in length provides the muscle’s greatest open kinetic chain activities whereas mechanically-produced torque at a the lower extremity functions primarily point in the range of motion which is in closed kinetic chain activities. important for holding heavy objects. It should be kept in mind that open In this instance, the torque that the chain activities often facilitate rapid muscle can produce actually movements whereas closed chain increases because of a mechanical functions are used to develop force change, even though the physiologic and power. muscle tension decreases. In functional upper extremity open chain activities such as throwing, the proximal portion of the extremity OT 2 (AY 2024-2025)  initiates the movement for the distal joints. In closed chain activities, compression of the joints occurs, providing stabilization through joint approximation and coactivation of opposing muscle groups. OT 2 (AY 2024-2025)