What is exercise( 운동 )? Exercise physiology 2011 년 2 학기 Shin Seung Sub A physical activity that is performed for the purpose of improving, maintaining or expressing a particular type of physical fitness. Training for or performing athletics, sports, or recreational activity Rollerblading, ice skating, swimming, jogging, etc. What is physical activity( 신체활동 )? An activity performed by the body for purposes other than the specific development of physical fitness. ADL such as shopping, gardening, work-related activities, house keeping, What is physical fitness( 체력 )? A state of bodily function that is characterized by the ability to tolerate exercise stress. Cardio-respiratory endurance Muscle performance Body composition Flexibility Agility Adaptation to exercise Acute adaptations The immediate structural and functional responses to exercise that function to help the body tolerate the exercise or physical activitiy Chronic adaptations The changes in body structure and function that are retained after repeated bouts of exercise What is exercise physiology( 운동생리학 )? A discipline involving the study of how exercise alters the structure and function of human body. Body systems, organs, tissues, cells and subcellular molecules 1
Introduction Basic Neuromuscular physiology Shin Seung Sub Skeletal muscle 체중의 40-45% 차지 430 개이상의근육, 사용빈도가높은근육은 80 개이하 Strength, Moving the bones, blood, food, air and etc. Mechanical energy heat energy Protection to the skeleton by Distributing loads & absorbing shock Dynamic work locomotion and positioning of body segments Static work maintain the body posture Structure of Skeletal Muscle 근막 근외막근주막, 근다발근내막 A sheath of connective tissue that surrounds muscle fibres. Human cell diagram 핵 [nucleus] DNA의복제, RNA합상. 세포질 [cytoplasm]: 소기관 + 사이트솔 세포핵 세포벽 세포내함유물등을제외한부분인세포질체를구성하고있는물질이세포질이다. 세포막 [cell membrane] 반투과성막으로물질이동의선택적관문역할 (selective barrier) 을한다 미토콘드리아 [mitochondria] 콘드리오솜또는사립체 ( 絲粒體 ) 라고도한다. 크기는 0.2~3nm로세포호흡에관여한다 형질내세망 [endoplasmic reticulum] 세포안의물질을세포밖으로운반하는데있다 ( 위선, 췌장 ). Muscle cell->muscle fiber 세포막 - 근초 (sarcolemma) 세포질 - 근형질 (sarcoplama) 형질내세망 - 근형질세망 (sarcoplasmic reticulum:sr) 2
Microscopic structure Microscopic structure I band "clear zone" around Z-line (Isotropic) Only actin resides A band "dark region" in center of sarcomere (Anisotropic) Actin and myosin overlap, titin (A- band part) cross-bridging takes place H zone "clear zone (Hessen s zone) in the center of sarcomere around M line Only myosin resides (tail part) M line mid point of the sarcomere Sarcomere( 근절 ) Basic repeat unit of striated muscle, delimited by Z-lines The functional unit of the contractile system in muscle Sarcoplasmic reticulum a special type of smooth ER found in smooth and striated muscle The SR contains large stores of calcium plays a major role in excitationcontraction coupling Thin filament Thin filaments consist primarily of the protein actin, coiled with nebulin filaments. Actin+ nebulin Tropmyosin Troponin complex Troponin C : TnC binds Ca 2+ and removes TnI inhibition Troponin T: TnT binds to tropomyosin Troponin I : TnI is involved in the inhibition of the actomyosin Mg 2+ -ATPase, Thick filament Myosin + Titin filaments Thick filaments consist primarily of the protein myosin, held in place by titin filaments. Cytoskeleton A cellular "skeleton" contained within the cytoplasm. The cytoskeleton is present in all cells It is a dynamic structure that maintains cell shape, protects the cell, enables cellular motion intracellular transport (the movement of vesicles and organelles, for example) cellular division. 3
Titin Titin Single molecule span from the Z- to M-line. Functions : regulates exact myosin(thick filament) assembly by acting as a giant template or "protein-ruler". an elastic connection between the end of the thick filaments and the Z-line. Giving muscle its passive tension and they also keep thick filaments centered between Z-discs. http://www.fbs.leeds.ac.uk/research/contractility/titin.htm Nebulin Nebulin is an actin-binding protein which is connected from Z-line in skeletal muscle. Function Acting as a thin filament "ruler" and regulates thin filament length during sarcomere assembly. A role in cell signaling, remain uncertain. Nebulin 1.α-Aktinin 2.Nebulin 3.Telethonin 4.Titin 5.M-Band 6.Head of Myosins 7. Z-line T-system T-system 4
Muscle contraction Muscle contraction 1. The nerve action potential 2. release Ach 3. sends a charge through the T-tubles 4. Ca ++ release from sarcoplasmic reticulum 5. Ca ++ bind with troponin C (actin) 6. Cross- bridging (muscle sliding) 7. Ca ++ removed (uptake by SR) 8. the myosin separate from actin, and another ATP molecule attaches to the head on the myosin Ca ++ is a very strong positive charge The force of the bending of the heads caused the ATP molecule to be released. Molecular basis of muscle contraction Sliding filament theory Cross-bridge mechanism Huxley, 1974 가장널리사용됨 각각의 cross bridge 의연결은 actin filament 위의수용기자리에서떨어지면서다른자리에재부착하는과정을 5-6 회반복 Attachment power stroke detachment 사람이줄을두손으로번갈아잡아당기는것과유사함 Eccentric muscle contraction Lombardi and Piazzesi, 1990 Eccentric muscle contraction Cross-bridge mechanism may be limited to explain isometric and eccentric muscle contraction Lombardi and Piazzesi (1990) suggested a different type of cross-bridge cycle. In the model, detachment of stretched myosin head occurs at an early stage of the cycle. Reattachment of cross-bridges is 200 times faster than attachment of cross-bridges which detach after completion of the cycle. The stretch stimulus of the contracting muscle occurs below the critical level of 10% of the maximum shortening contraction. Types of muscle contraction Dynamic work: mechanical work, joint motion produced Isotonic: Muscle tension is constant. Nonphysiologic Concentric The contractile force exceed the external force Allowing the muscle shortening Eccentric when the external force is greater than the internal force as occurs when lowering a load. Allowing the muscle shortening Isokinetic muscle contractions where motion velocity is kept constant. 5
Types of muscle contraction Static work: No joint motion, posture or position maintained Isometic: muscle length does not change during a contraction. Muscle contraction types Elbow flexion in standing Elbow flexion on supine 운동단위 (The Motor Unit) The Motor Unit The basic level of nervous system organization of the muscle is the motor unit, and its associated alpha motor system. Lower motor neuron + axon + muscle fiber The number of muscle fibers per motor unit The higher innervation ratio Fine movement The extraocular muscles = 3:1 The lower innervation ratio Strength production The gastrocnemius muscles = 2000:1 근수축강도의단계 (Gradation of strength of muscle contracion) Initially, the smallest innervation ratio Increasing the number of motor units activated simultaneously (recruitment) Increasing the frequency of sitmulation of individual motor unit. 동원의크기원리 (The size principle of recruitment) When a muscle contraction occurs, motor unit recruitment is based upon the size principle. First, The smallest muscle fibers/motor unit recruited Later recruited the larger muscle fibers/motor units. As the muscle demands increase, the firing rate moves from slower to higher frequencies. The motor unit recruitment strategy can move from an asynchronous to a synchronous pattern. 6
The size principle of recruitment The types of Muscle fibers First, The smallest muscle fibers/motor unit recruited Later recruited the larger muscle fibers/motor units. As the muscle demands increase, the firing rate moves from slower to higher frequencies. The types of Muscle fibers Fiber Type Slow Twitch (ST) Fast Twitch A (FT-A) Fast Twitch B (FT-B) Contraction time Slow Fast Very fast Size of motor neuron Small Large Very large Resistance to fatigue High Intermediate Low Activity used for Aerobic Long term anaerobic Short term anaerobic Force production Low High Very high Mitochondrial density High High Low Capillary density High Intermediate Low Oxidative capacity High High Low Glycolytic capacity Low High High Major storage fuel Triglycerides CP, Glycogen CP, Glycogen 근섬유의종류와특성 (The variety of Muscle works) Small, low nerve fibers develop Slow-twitch muscles. Smaller size and produce less tension Tonic movement( 긴장성 ) - stability( 안정성 ) Postural activity- Isometric contractions ( 등척성 ). Large, fast nerve fibers develop Fast twitch muscles. Larger size and produce more tension Phasic movement( 위상성 )- mobility( 운동성 ) Limb movement- Isotonic contractions ( 구심성, 원심성 ). Most muscles contain a mixture of Fast and Slow-twitch muscles. Effect of skeletal muscle architecture Effect of skeletal muscle architecture 근육의횡단면적과근육의장력은비례함 근육이생산하는속도와가동역은근원섬유의길이에비례함 장력 방추근 < 익상근 수축거리 방추근 > 익상근 7
Effect of skeletal muscle architecture 동일한근육이 30 도의익상각을가질경우 86% 의힘만전달됨. 즉. 익상근 ( 익상각이 30 도일때 ) 은방추근근력의 86% 만사용하여동일한물건을들수있다. 절대근력 absolute muscle strength 횡단면적 1 cm2당 3-4 kg Length-Tension Relationships The strength of the contraction is greater when the muscle is elongated to about its midpoint (normal resting length) of the filament sliding range. Length-Tension Relationships Neural control Motor unit 의동원이많을수록근력은증가한다. Proper coordination of movement among agonist, antagonist, and synergist muscle groups is also necessary for optimal control and function Individual s age 노화 (Aging) 근내막과근외막의결합조직의농도의증가 근섬유수의감소 하지의근력의상지보다먼저감소함 Isometric strength 보다 isotonic strength 가먼저감소함 Cognitive strategies Positive cognitive strategies increase the muscle strength Arousal, attention, imagery and selfefficacy Emotional arousal increase the tone (strength) about 10% Mental practice 8