Structure – Function - Performance • Muscle Structure Physiology and Biochemistry • Muscle Function of Running • Muscle Performance Muscle Structure and Function Chapter 1 Muscle Structure: Muscle Structure Classification •Smooth • Human body contains over ___ skeletal muscles • ____________________ • Spindle shaped – _______ of total body weight • Uninucleated • Characteristics •Striated – Irritability – Cardiac • Autonomous system • Ability to respond to a stimulus • ___________________ – ______________ • Cylindrical • Ability to shorten –Skeletal • Voluntary control – Extensibility • Cylindrical • Ability to lengthen • ____________________ – Elasticity • Striated • Ability to return to resting length Structures in a typical cell Gross Structure of Muscle • ___________ – Surrounds entire muscle • ___________ – Surrounds bundles of muscle fibers • Fascicles • ___________ – Surrounds individual muscle fibers Fig 8.1 1 • Sarcolemma: Muscle cell membrane • Myofibrils Threadlike strands within muscleMicrostructure fibers – ______________________ – ______________________ of Skeletal • Elastic tissue (proteins) –Sarcomere within the sarcomere. • Z-line, M-line, H-zone, A-band & I- – _____: extends from the bandMuscle Z-disc to the M-line. – Elastic in PEVK region • amino acids: proline, glutamate, valine, and lysine – ___________________ __________________. • Connective tissue related to fatigue? – Weight bearing vs. non- weight bearing. – “hitting the wall” Fig 8.2 Neuromuscular Junction • ______________________________________________________ • Motor end plate: pocket formed around motor neuron by sarcolemma • Neuromuscular cleft: short gap • Ach is released from the motor neuron • Within the sarcoplasm – Causes an end-plate potential (EPP) • Depolarization of muscle fiber – Sarcoplasmic reticulum • __________________ – Transverse tubules – Terminal cisternae – Mitochondria Fig 8.3 Fig 8.4 Muscle Structure Muscle Structure Key components in the muscle cell Key components in the muscle cell • Mitochondria • Fat Droplets – Within muscle cell (in – Fats generally stored in cytoplasm) fat cells – Main function: ___________ – …but, can be stored in _______________________. muscle cell as triglyceride – Location of oxidative molecules conversion of foodstuffs into • ____________________ useable cellular energy ____________________ – Limiting factor in running – Source of energy endurance performance? • lipolysis; enzyme: lipase 2 Muscle Structure Muscle Structure: Key components in the muscle cell Fiber Type • ________________________ – Oxidative • Glycogen – High content of myoglobin • Myoglobin transfers O2 carried in blood to mitochondria – Polysaccharide (i.e., animal starch) and act as a oxygen store in muscles – Lots of glucose molecules – Slow contraction time vs. Type II – _________________: Breakdown of • …but contraction time for some athletes may be glycogen to glucose comparable to Type II contraction times of non- – _________________: Formation of athletes. glycogen from noncarbohydrate – Fatigue resistant sources • ________________________ – _________________: Formation of – At least 5 subtypes (IIa, IIb, IIc, IIab, IIac) glycogen from carbohydrate sources – Type IIa – Glycogen stored in muscles and liver • Oxidative-glycolytic – Total glycogen storage is relatively • Intermediate – can be fatigue resistant small and can be depleted in a few Type I – Type IIb (slow oxidative) hours of exercise • Glycolytic • High force production Type IIa • Short duration (fast oxidative) – Type IIc • uncertain origin Type IIb • Capable of being developed to I or IIa? (fast glycolytic) • More power than IIb Muscle Fiber Types Muscle Function • Primary functions related to human movement: Fast Fibers Slow fibers – _________________ Characteristic Type IIb Type IIa Type I – Maintain Posture Generate Force Number of mitochondria Low High/mod High – Stabilize Joints Resistance to fatigue Low High/mod High • Other functions: Predominant energy system Anaerobic Combination Aerobic –Protection ATPase Highest High Low – ________________________ Vmax (speed of shortening) Highest Intermediate Low –… Efficiency Low Moderate High Specific tension High High Moderate Muscle Contraction Muscular Contraction – CNS signal • The sliding filament model – __________________________________ – Muscle shortening occurs due to the __________________________________ movement of the actin filament over the – Upon reaching post-synaptic membrane myosin filament threshold, signal is transmitted throughout – ___________________________________ muscle fibers of a motor unit (α motor neuron ___________________________________ and all innervated muscle fibers). – Reduction in the distance between Z-lines of the sarcomere 3 The Sliding Filament Model Actin & Myosin Relationship •Actin – Actin-binding site – Troponin with calcium binding site – Tropomyosin •Myosin – Myosin head – Myosin tails Fig 8.5 Fig 8.6 Energy for Muscle Contraction • ________________________ is required for muscle contraction – Myosin ATPase breaks down ATP as fiber contracts • Sources of ATP – Phosphocreatine (PC) – Glycolysis – Oxidative phosphorylation Is the myosin binding to actin firm or a seris of loose couplings (Figure 1.6, p11)? Muscle Function: Muscle Function: Role of Muscle Muscle Action • _____________: (prime mover) functions to cause • ________: No change in muscle length a movement • ________: Change in length (same external weight) • _____________: functions to resist movement –Concentric • Stabilizer: functions to fixate an area so another • muscle length shortens during contraction movement can occur – Eccentric • Synergist: assist another muscle • muscle length increases during contraction • ________: Angular speed is constant during contraction • Neutralizer: functions to prevent undesired –Concentric movement – Eccentric 4 Muscle Performance Muscle Performance: Angle of Attachment and Pennation • How well muscle functions are carried out. – i.e., ability to generate force • Factors that influence muscle performance: – Angle of attachment and pennation – Length-tension relationship – Force-velocity relationship – Fatigue • Length-Tension Relationship Muscle Performance: of Muscle Contraction Force – Velocity Relationship – _____________________ _____________________ _____________________ _____________________ – Muscles that cross two joints • concurrent movements at both joints not maximized . Fig 8.17 Muscle Performance Fiber Type Composition Fiber Type Sprinters vs. Endurance Athletes •Force Type of Athlete Type I Muscle Fibers (%) • Contraction velocity Sprinters 26 •Power Sprinters and Jumpers 37-39 Weight lifters 44-49 – ______________ Cyclists and swimmers 50 – Rate of transformation of chemical to Middle-distance runners 45-52 mechanical energy Elite half-marathon runners 54 Canoeist 60 • Fatigue resistance Elite rowers 60-90 Elite distance runners 79-88 Cross-country skiers 72-79 5 Fiber Type Composition Training Sprinters vs. Endurance Athletes Different physiological and physical requirements of sprinters and • Purpose: __________________ distance runners – General tiredness (Taber’s) – Reduction of force generating capability of muscle Attribute Sprinter Distance Runner • Develop muscle fiber types by training at different intensities. Size Large (>80kg) Small (<50kg) • Muscle recruitment based upon: – ____________________ Explosive Power Very high High • related to intensity of exercise – Long slow distance: Type I Aerobic capacity Unimportant Important – High intensity: Type II – _________________________________________ Fatigue resistance Unimportant Crucial • Muscles are recruited based upon information received by the CNS – Cardiostat: control based upon O2 supply to the heart or brain – Glycostat: control based upon blood glucose (protect brain?) Muscularity Essential Disadvantage – Thermostat: control based upon heat accumulation • Protect the body from harming itself Body type Mesomorphic Ectomorphic – Central fatigue • Neurotransmitters within brain change signals being sent to muscles. Muscle fiber 80% Type II 60% Type I – Is muscle recruitment influenced by a perception of how much more work compositions can be done? “Only the fast and strong die young” Summary • Endurance athletes tend to outlive • Muscle Structure sprinters. – Gross to cell level – Muscle fiber type – Health benefits from endurance exercise? • Muscle Function – Related to muscle fiber type? – Generate force • Fiber type influences chosen level of physical • Sliding filament theory activity? • Muscle Performance • People with more Type II muscle fibers may be – Length tension more prone to developing hypertension, diabetes – Force velocity and obesity (Bassett, 1994). – Angle of attachment • People with more Type I fibers have greater levels – Fatigue of blood HDL-cholesterol (Tikkeanen et al., 1991). –Training 6.