Week Two - Skeletal Muscle Structure and Function and Principles of Resistance Exercise Design

What is the individuality principle?

· Genetic factors/individual traits clearly interact to influence the training response. } · Also consider initial fitness level

What is the art of applying specific exercise principles?

· Intensity · Duration · Frequency · Might be optimized for aerobic training to move from Being sedentary to Obtaining basic functional health

What is an isolated movement?

· Isolated Movement isolated to one joint

What is isometric?

· Isometric: Tension generate by the muscle produces a Torque which does not exceed resistance torque No change in distance between muscle Attachments

What are general training principles?

1. Overload 2. Recovery 3. Specificity (and generality) 4. Individuality 5. Reversibility

Why can't we shift heavy weights as quick as lighter weights?

Actin - myosin cross bridge connections occur at a set rate. If the velocity of contraction is faster than that rate then less cross bridges form, therefore force is decreased.[Force-velociy relationship] [Good test question] · As the velocity of a concentric muscle action increases, the maximum force able to be produced decreases. · Velocity is speed with direction. Negative velocity means eccentric

How does fatigue effect movement?

Fatigue-effects on Movement · Watch for:[TA1] o Changes in movement control o Cheating movements o Changes in range of movement o Changes in velocity of movement [TA1]People become uncoordinated w their movements

· Why when you are weak does it take longer to move?

It takes longer to move something when you are weak because you need strength to improve power

What is the force velocity relationship?

Strength is velocity dependent

What are myofibrils?

The Myofibrils are Bundles of Sarcomeres Connected in Series

What are energy saving springs?

· Relatively compliant tendon · Achilles tendon stores and returns a significant amount of mechanical energy

What is titin?

o Titin is the primary source of passive tension [Spring/elastic tension] in and between sarcomeres. Titin has an elastic quality. Causes an increase in tension at end of range.

What is the "Popping Sarcomere" hypothesis?

· "Popping Sarcomere" hypothesis (Morgan,1990) o sarcomeres that are slightly longer have less overlap and generate lower forces. o shorter stronger sarcomeres pull the weaker longer sarcomeres apart. · Tends to damage type IIb fibres (fast glycolytic ) - possibly because these are preferentially recruited in eccentric muscle actions.

What is the difference between terms weightbearing and non weight-bearing?

· "Weight bearing" refers to body weight · "Non weight bearing" refers to wieghts

What are the types of muscle fibre?

· 3 types of motor unit - 3 types of fibre. · Skeletal muscle contains 3 main types of fibers that differ in: o The primary mechanisms they use to produce ATP o The type of motor neuron innervation. · The proportions of each type of muscle fiber vary from muscle to muscle and from person to person. Power more type II. Endurance more type I

What is Causes of Fatigue-Peripheral?

· ATP - 2-3 seconds MVC CP + ADP→C+ ATP (CP=creatine phosphate) · CP drops depending on the workload · Glycogen and fat mobilised · Glycogen depletion - "hit the wall!" · Reduced cross-bridge cycling (needs ATP)

How is ATP used in muscle contraction?

· ATP is the common currency · Splitting ATP produces energy · This energy is used to detach actin from myosin and cock the head of the myosin ready for action.

What is the agonist?

· Agonist: The agonist muscle group is the prime mover for the particular movement.

What are the four principles of specificity in resistance exercise program design?

· All training adaptions are specific to the stimulus applied. 1. Muscle action or test specificity 2. Velocity specificity 3. Muscle group specificity 4. Energy Source specificity · Understanding this is VERY important to being an effective prescriber of exercise

Do you want adaptations to favour the anaerobic or aerobic pathways?

· Anaerobic-Muscle hypertrophy, better storage and usage of anaerobic energy stores (glycogen and ATP/PC) = Strength, Power improvements · Aerobic- Cardiovascular adaptations favouring better transport (HR and SV and haemodynamic changes) and utilisation of oxygen (increased capillary density and mitochondria stores in muscle)= Endurance

What is the antagonists?

· Antagonists: The antagonistic muscle group is the opposing group usually on the opposite side of the joint. [Typically slow or control that movement]

What is the role of calcium in muscle contraction?

· C a2+ binds to troponin-tropomyosin in the actin filaments, releasing the inhibition that prevented actin from combining with myosin

What is closed chain exercises?

· Closed Chain (upper limbs): Distal segment of extremity Fixed to ground or supportive surface

What is a compound movement?

· Compound Movement involving more than one joint

What is concentric?

· Concentric: Muscle torque exceeds resistive torque. Decrease in distance between muscle attachments

What is delayed onset muscle soreness (DOMS)?

· DOMS is caused by unaccustomed high intensity physical activity - usually with an eccentric component. o Starts 8 hours after exercise and peaks in the next 24 - 48 hours. o Muscle tenderness, pain on palpation, stiffness

Learning Outcomes?

· Describe the micro and macro structure of skeletal muscle · Describe excitation-contraction coupling · Describe the cross-bridge cycle hypothesis · Explain the length tension relationship · Explain the muscle physiology of isometric, eccentric and concentric muscle actions. · Describe tendon structure and function · Define the motor unit and describe motor unit recruitment principles · Describe the properties of the different types of muscle fibres · Discuss the role of the sensory system in movement control · Operationally define muscle strength, endurance and power in relation to muscle performance. · Describe and explain the factors that influence muscle performance · Draw and explain the force-velocity relationship for contractions of different velocities. · Describe the effects of fatigue on muscle performance · Discuss Exercise Induced Muscle Damage (EIMD

How does overload/progression work together?

· Determine when & how to change FITT of training · It suggests that Improvements occur by imposing new & higher training demands on your client. To ensure that they are successfully adapting to training

How does muscle fibre alignment differ?

· Differences in sarcomere alignment and length strongly affect a muscle's force- and power-generating capacity o Fusiform o Pennate · Pennate muscles differ from fusiform fibers in three ways: o They generally contain shorter fibers o They possess more individual fibers o They exhibit less range of motion

What is exercise induced muscle damage?

· EIMD · Damage related to strain (length changes) rather than stress (forces). · Cause a loss in force production 10 to 60% of MVIC

What is the force velocity relationship in eccentric muscle actions?

· Eccentric muscle actions the muscle absorbs energy produced by the external load. · Can produce more force that concentric and isometric muscle actions. · Force is independent of the velocity of contraction. · Require less activation for the same force

What is eccentric?

· Eccentric: Muscle torque remains less than resistance torque Increase in distance between muscle attachments

What is the relationship between tension and fatigability?

· Fast fatigable motor units produce largest tension for stimulation. · Slow motor units maintain tension with repetitive stimulation

What is fatigue?

· Fatigue is the decline in muscle tension or force capacity with repeated stimulation or during a given time period · Voluntary muscle actions exhibit four main components: o Central nervous system o Peripheral nervous system o Neuromuscular junction o Muscle fiber o Fatigue occurs at multiple sites central and peripheral · As muscle function changes during prolonged exercise, additional motor unit recruitment maintains force output necessary to maintain a constant level of

What is the recovery principle?

· For maximum performance benefits and before a training stimulus is reintroduced, complete recovery from the previous stimulation must occur (after Rushall and Pyke, 1990) · Warm-down · Interval between sessions · Varying factors in each session · Speed at which your clients can recover is dependent on their: o FITT o Other individual factors: o Age § Experience § Environment § Amount of sleep § Nutrition § Fluids

What is the fibre size and angle of fusiform fibres?

· Fusiform or spindle-shaped fibers run parallel to the muscle's long axis and taper at the tendinous attachment o The fibers run parallel to the muscle's long axis so fiber length equals muscle length o This arrangement facilitates rapid muscle shortening

What is Slow Twitch-Type I?

· Generate energy for ATP resynthesis predominantly through the aerobic system of energy transfer · Are highly fatigue resistant and ideally suited for prolonged aerobic exercise · Are slow-oxidative fibers with slow shortening speed and rely on oxidative metabolism

What is exercise effect on fatigue?

· Low intensity efforts o activities which are very low intensity will use mostly slow twitch fibres fatigue resistant. o central fatigue due to substrate depletion of CNS o Neurotransmitter changes · High intensity efforts o dynamic resistance exercise, high intensity anaerobic exercise. Anaerobic energy sources deplete quickly (ATP-PC and anaerobic glycolytic system) o fast twitch fibres are less fatigue resistant and show peripheral fatigue

What is the tendon structure and function?

· Made of collagen. wavy "crimp" pattern at rest. · Fibrils bundled into fascicles and then into tendons. · Attach muscle to bone · Function to transmit force and slide in movement. · Low blood supply (white) so heal badly. · Viscoelastic properties

What is the specificity principle?

· Maximum benefits of a training stimulus can only be obtained when the training stimulus replicates the movements and energy systems involved in the activities of the sport (performance) (after Rushall and Pyke, 1990) · "Simply stated, specific exercise elicits specific adaptations to promote specific training effects" · Refers to consistent observation that o Specific adaptations occur based on specific neuromuscular demands designed into program of exercise · When you design an exercise program o You should think specifically about how they will need to train

What are factors influencing overload?

· Mode of activity · Volume - How much? Frequency? Time? · Intensity (relative stress) · Repetitions/Duration (work done per session) · Frequency (sessions per week) · Program length · Initial fitness level · "Small stimuli are useless, moderate stimuli are useful, and excessive stimuli are harmful"

How do you generate maximal power?

· Muscle morphology adapted for strength · Rapid energy supply [Strength and power] o Sphospho-creatine (PCr) supplies o effective glycolytic metabolism o effective oxidative recovery system · Rapid, appropriate activation [Coordination] o recruitment of high threshold motor units o training requires maximal effort o rapid firing of MNs o ballistic power training o synergist coordination o decreased co-activation of antagonists o muscle environment

How does muscle fibre architecture effect function?

· Muscles are designed for their function. · Hamstrings o Small PCSA (not an antigravity muscle) o Low forces over a large range · Soleus o Large PCSA, pennated. - o Antigravity o High forces over short range

What is maximal endurance?

· Muscles full of mitochondria · Sustained energy supply during exercise o supply of carbohydrate o supply of oxygen · muscle environment · conscious self-regulation of sub-maximal power output - pacing

What happens at the Sarcomere and Tension Development Sliding Filament Mode?

· Myosin cross bridges cyclically attach, rotate, and detach from the actin filaments with energy from ATP hydrolysis · This produces a change in relative size within the sarcomere's zones and bands and produces a force at the Z bands · I band decreases as the Z bands are pulled toward the centre of each sarcomere

What is velocity specificty?

· Need to train at velocity required in sport/ADLs/hobbies · Control at higher velocity requires training and strength Individual's ability to recruit, rate code, & synchronize a large number of fast-twitch fibers rapidly · For example: Consider the velocity of muscle action required for the following shoulder extension tasks. Similar muscle groups are used but at different velocities

What is muscle group specificity?

· Need to train muscle groups required in sport or rehabilitation. · Need to consider the following: 1. Agonists 2. Antagonists 3. Synergist 4. Stabilizers · For example: The exercises below have muscle group specificity for pull phase in freestyle

What is energy source specificity?

· Need to train the energy systems required in sport or recreation: · Anaerobic Energy Source - short duration bouts of exercise high intensity. Less rest between sets · Aerobic Energy Source - longer duration bouts of exercise lower intensity more rest between sets

What is nerve conduction?

· Nerves are conduits for electrical messages · The electrical message is conveyed by wave of electrical charge across surface of the nerve fibre to the neuromuscular junction. Alpha motor neurone stimulates a bundle of muscle cells grouped together (which is called a motor unit)

What is the nerve supply to muscle?

· One nerve or its terminal branches innervate at least one of the body's approximately 250 million muscle fibers. · The number of muscle fibers per motor neuron generally relates to a muscle's particular movement function

What is open chain exercises?

· Open Chain (upper limbs): Distal segment not fixed and allowed to move freely in space

What is the fibre size and angle of pennate fibres?

· Pennate fibers lie at an oblique pennation angle and allow a large number of fibers into a smaller crosssectional area o Unipennate, bipennate, multipennate o The degree of pennation directly impacts sarcomere number of fibers per cross-sectional muscle o Pennate muscles tend to generate considerable power

What is Fast Twitch-Type II?

· Rapid energy generation for quick powerful muscle actions. predominates in anaerobic-type sprint activities and other forceful muscle actions that rely almost entirely on anaerobic energy metabolism. · Type IIa A fast-twitch fiber with a higher oxidative capacity [Ability to regenerate ATP in oxidative fashion] · Type IIb A fast-twitch fiber has low oxidative capacity[Depends on ATP Phosphate-Creatine System Heavy Weight Lifting]

How Do We Regulate Muscle Force?

· Recruit more motor units. · The most effective method of increasing muscle force.

What is central fatigue?

· Reduced cortical drive (Gandevia 2001) · Measured by twitch interpolation or TMS - zap the brain and measure EMG in muscle. · The CNS uses lots of glucose for aerobic metabolism and fatigues easily.

What is Causes of Fatigue-Calcium?

· Reduced sarcoplasmic reticulum reuptake in Ca - delayed relaxation (needs ATP) · Reduced SR release (needs Ca in SR) · Muscle cramping is one symptom of muscle fatigue

What is the reversibility principle?

· Refers to o Loss of health or physiological training benefits that have resulted from a regular program of exercise

What is the neuromuscular junction?

· Represents the interface between the end of a myelinated motor neuron and muscle fiber and transmits the nerve impulse to initiate muscle action. · Action Potential→Synaptic vesicles in the end of the nerve release the neurotransmitter acetylcholine (ACh) into the synapse. · The post synaptic membrane receives ACh [TA1] and depolarises sending an impulse in all directions across the sarcolemma. [TA1]Acetyl-Choline

What happens at the sarcoplasm?

· Sarcomeres are contractile structures. Sarcomeres lengthen and shorten, developing tension on attached structures. Once the calcium ions hit

When is muscle tension development least?

· Sarcomeres produce most force at mid range · Found by electrically stimulating a muscle fibre at different lengths and measuring the force it produces

What are the short term and long term effects of DOMS?

· Short term effects: o DOMS reduces proprioception - not recommended if position sense is important in the next few days. · Long term benefits: o DOMS indicates damage, but damage can stimulate hypertrophy. o not recommended in degenerative muscle disease. o Protective effect of rebuilding muscle. Allows adaptive processes to happen

What is stabiliser?

· Stabilizer: Stabilise the proximal and/or Distal joints to allow prime movement to happen

How does fibre size and fibre angle effect strength?

· Strength is affected by fibre angle. · Muscles with similar anatomical cross sectional areas (blue line) may have different Physiological Cross-sectional areas (green line) (PCSA). · Which muscle is strongest? Pennate muscles B and C are stronger

What is the synergist?

· Synergist: Assists the agonist through the desired plane of movement.

How does overload lead to muscle morphology adaptations?

· Tension overload provides the stimulus for skeletal muscle adaptation. · Resistance training provides the mechanism by which overload is applied to skeletal muscles. · Muscle Fibre Hypertrophy - balance of protein synthesis and degradation favours the former o Repeated muscle fibre injury ® thicker and number myofibrils/fibre,

What is power?

· The ability of a muscle or muscle group to exert a large amount of force at a fast rate [TA1] (Zachazewski et al.,1996). [TA1]Time dependent

What is endurance?

· The ability of a muscle or muscle group to perform repeated contractions against a resistance (Zachazewski et al.,1996).

What is the T-Tubule System

· The action potential (AP) flows down the T-Tubule system to the sarcoplasmic reticulum. · The sarcoplasmic reticulum releases calcium ions into the cytoplasm of the muscle cell (sarcoplasm). · Calcium ion are necessary for contraction. "Activates" the actin filaments

What is stength?

· The maximum force a muscle or muscle group can exert at a specified velocity of contraction (Zachezewski et al.,1996).

What is a motor unit?

· The motor unit consists of the anterior motor neuron and the specific muscle fibers [TA1] iit innervates. o The individual and combined actions of motor units produce specific muscle actions o Each muscle fiber generally receives input from only one motor neuron, yet a motor neuron may innervate many muscle fibres o Each motor unit is made up of the same fibre types [TA1]Fast twitch and slow twitch

What is Henneman's Size Principle?

· The recruitment of motor units within a muscle proceeds from motor units with small axons (slow) and smaller number of fibres to motor units with large axons and larger number of fibres (fast).

What does viscoelastic mean?

· Viscoelastic means the material has elastic properties and viscous properties · Elastic like an elastic band. · Viscous like honey - it slips (damping forces).

What is the all or nothing principle in relation to motor neurons?

· When a motor neuron is stimulated, all of the muscles fibres in that motor unit contract to their fullest extent or not at all. · The threshold stimulus of the sarcolemmas of each fibre must be met for contraction to occur at all. Hence the ALL or NOTHING PRINCIPLE

What is the overload principle?

· When a tissue is subjected to a training stimulus that causes strain, the body will reorganise its capacities so that the next exposure to the same stimulus will produce less strain, given that sufficient recovery has occurred between exposures (after Rushall and Pyke, 1990)

What happens when muscle stimulation ceases?

· When muscle stimulation ceases, intracellular Ca2+ concentration rapidly decreases as Ca2+ moves back into the lateral sacs of the sarcoplasmic reticulum through active transport that requires ATP hydrolysis · Ca2+ removal restores the inhibitory action of troponin- tropomyosin · In the presence of ATP, actin and myosin remain in the dissociated, relaxed state.

What is muscle action specificity?

· You need to make sure your training the desired muscle action based on the needs of your patient. · Further more, if you train isometrically and assess with concentric/ eccentric little or no strength increases will be noted. · Consider the following: 1. Open or Closed Chain 2. Compound or Isolated 3. Weight Bearing or Non Weight Bearing 4. Concentric/Eccentric/Isometric 5. Joint Range Moved Through 6. Movement Plane