Applied Muscle Physiology

Precautions during resistance training

Precaution=don't stop exercise, just monitor, decrease resistance, change something to prevent substitute motions/fatigue Valsava: avoid during exercise b/c increase BP significantly ("don't hold your breath"), have patient exhale with each resisted effort -exhale through the "sticking point" (end of concentric phase) Substitute motions/fatigue Overtraining: decline in physical performance when performing high intensity/high volume strength and endurance training, brought on by inadequate rest, too rapid progression, and inadequate diet/fluid

Muscle Performance

Primary factors that determine performance characteristics of skeletal muscle include fiber type and muscle architecture.

Muscle performance

Refers to capacity of a muscle to do work Work=ForcexDistance (W=FxD) The key elements of muscle performance: strength, power, endurance

Hennerman "Size Principle"

Smaller motor units recruited 1st and then as more force is needed, larger motor units are recruited. Deactivated in reverse order. Makes sense b/c Type I can last longer due to O2 energy system. Small asons supply motor units generating less tension than those with large axons. Units generating largest forces were subject to fatigue at high rates of stimulation.

Definitions: Strength, Muscle Power, Endurance

Strength: broad term that refers to ability of contractile tissue to produce tension. Greatest measurable force that can be exerted by a muscle or muscle group to overcome resistance during a single, max effort. Assesed in terms of force, torque, work, and power. Muscle Power: related to the strength and speed of movement and is defined as work produced by a muscle per unit of time. Power = W / time Endurance: broad term that refers to the ability to perform low-intensity, repetitive, or sustained activities ove ra prolonged period of time. Cardirespiratory (total body) endurance, muscle endurance.

Determinants of Resistance exercise: Intensity

Submax load (mod. to low): beginning of exercise program, early stages of soft tissue, after periods of immobilization (cartilage), children and elderly, goal = endurance, warm up adn cool down, during slow velocity isokinetic training Near max. or max load: goal is to increase muscle strength and power and size, otherwise healthy adults is last phase of rehab program, conditioning program for individuals with no pathology, training for competitive weight lifting or body building

Stimulus Factors Affecting Muscle Tension: Summation

Successive stimuli before relaxation phase has completed. Relaxation is starting to occur in the 3rd twitch, but before it occurs another stimulus comes down which causes more twitch and increased tension in the switch. *Greater contraction forces may also be achieved by increasing the frequency of motor unit activation. Tetanus - nice smooth reaction when stimulus frequency is high enough (ultimately what we want).

Muscle (local) Fatigue

Things to watch for because there may be visual signs of fatigue that the pt won't tell you about. Diminished response of muscle to repeated stimulus and is reflected by a progressive decrement in the amplitude of the motor unit potentials. Normal, reversible, and temporary. Type I - less prone to fatigue Type II - fatigue quickly Signs and Symptoms of muscle fatigue: Uncomfortable sensation (pain/cramping), tremulousness, jerky movement, inability to complete full ROM, substitution, inability to continue low-intensity physical activity

Ultrastructure

Titin holding the thick filament in place from the Z-line. If you move pt. through whole range and it's stiff -> titin issue. Decreased ROM due to tightness -> lack of sarcomeres -> stretching will improve. Passive ROM - motion within available range. Stretch - goes beyond availabe range.

Isokinetic-Velocity Spectrum

Typically medium (60-180d/s) and fast (180-36-d/s) speeds are slected 15d/s carryover (therefore 30d/s increment) 1-2 sets of 8-10 to 20 reps at each speed, typically 3-4 speeds Rest 15-20 seconds between sets and 60 seconds between speeds

1. What are the consequences of isometric contractions in regards to work?

W=FxD Fx0=0 NO work done in isometric contractions because there is no change in length

Which is a better test of strength: an isometric or dynamic muscle contraction?

Would depend on what you're looking for. If it's just force, then isometric. If it's functional, then dynamic.

Determinants of Resistance Exercise Program

Alignment: determined by direction of pull of muscle fibers, line of gravity important when using body weight or free weights Stabilization: external versus internal (by supporting muscles) Intensity: submax (<50%) vs. max (near max=70%) Volume: reps and sets Frequency Duration Mode Rest Interval Integration of function - ULTIMATE GOAL

Strength and Endurance

Are associated, yet they do not always correlate well with each other.

Determinants of resistance exercise: frequency, duration, rest

Frequency: the greater teh intensity and volume, the more time necessary for recovery. Volume and intensity low, daily. As increased, every other day (5x/week). Maintenance (2x/week). Highly trained (6x/week). Duration: for significant changes: 6-12 weeks Rest intervals: 8-12RM 30-60seconds, 3-5RM 1-2 min, moderate intensity 48 hours between sessions

Muscle Length - Tension Relationship

Generally, depending upon muscle involved: greatest amount of tension can be developed when a muscle is stretched between 100% to 130% of its resting length. Stretch beyond 100-130% resting length significantly decreases the amount of force muscles can exert. A proportional decrease in ability develop tension occurs as the muscle is shortened. When shortened to around 50-60% or resting length ability to develop contractile tension is essentially reduced to 0.

Considerations for Implementing Resistance Exercise

Healing status of tissue, training status (novice or elite), presence of pain, ultimate goal (stability-isometrics, strength-isometrics, eccentric, concentric, isokinetics), SAID principle

Progression

How? When?: If they don't fatigue/it's too easy with sets/reps, then increase reps, sets, decrease rest, or increase challenge (more dynamic). Ask to do as many sets as they can. If alot, increase the weight. Trial and error. Depends on injury: is tissue healing or just a weakness? Muscle Size?

Determinants of resistance exercise: Strength, endurance, power

Is goal to improve strength, power, muscular endurance, or all? Strength: DeLorme, Oxford, DAPRE, novice (60-70% 1RM x 8-12 reps) Endurance: Light loads with high volume, 3-5 sets, 10-25 reps Power=work/time

Types of resistance exercise: dynamic concentric/eccentric

Isotonic? Everyday activities use combinations of concentric and eccentric contractions (specificity?) Eccentric training is also thought to be an essential component for prevention of injury or reinjury during activities that involve high intensity deceleration and quick changes of direction When muscle is very weak (<3/5), active eccentric contractions against no external resistance may be easier than concentric) Cross training effect: slight increase in strength of the same muscle group on the opposite side, PNF concept of overflow/irradation

Muscle Architecture

Large PCSA = max force = parallel (short, broad muscle - glutes, pecs, vastus lateralis) Small PCSA = max excursion/displacement (amt. a muscle can shorten) = series (long, thin muscle - sartorius, gracillis) Max velocity - series (greater distance in shorter amount of time)

Determinants of resistance exercise: mode

Manual, mechanical (elastic tubing/therabands, free weights - only safe and effective at slow to mod speeds, resistance machines -constant or variable, accomodating, speed specific training, very little transfer of training to other speeds), body weight/gravity, water *Manual tech: easily modifiable, but hard to quantify, ex: PNF *Free wts: safety considerations, speed, gravity, ability to hold wt

Progressive resistive exercise (PRE)

Many protocols have been developed Training induced strength gains occur with 2-3 sets of 6-12 reps of a 6-12RM

Muscle Length - Tension Relationship

Maximal ability of a muscle to develop tension and exert force varies depending upon the length of the muscle during contraction. Active tension due to cross-bridges. Passive structures also produce tension: conn. tissue, fascia. Adding both passive and active together gives you total tension.

Skeletal Muscle

Muscle -> fasicles -> muscle fibers (cells) -> myofibrils -> sarcomeres (sarcomeres arranged in series and parallel) *Myofibril - where hypertrophy occurs *Sarcomeres - basic contractile unit

Age

Muscle pass peaks: women-16-20 yrs, men-18-30 yrs Strength production capacity peaks: 18-30 yrs Starting at 3rd decade, strength declines 8-10% through 5th and 6th decades, strength declines 2-4% per year for 6th 7th decades. *But body can adapt to strengthening exercise throughout lifespan Neural factors significant mechanism and fatigability and need for rest increases with age Force production has to do with recruitment in older clients, increase neural capacity not hypertrophy.

Atropy

Muscles do not atrophy at the same rate. Immobilization: (casted) position of limb and length of muscle during immobilization (lengthened muscle will atrophy less than shortened due to sarcomeres and not losing them) Unloading: (astronauts) Muscles with high % of ST atrophy to a greater extent than those with high % of FT Aging: reducton in Type II fibers > 50 y.o (both WB and NWB muscles) Stroke: reduction in Type II fibers, regardless of age, decrease Type I diameter, decrease CSA

Determinants of resistance exercise: integration of function

Must address core stability and dynamic mobility (stabilization exercises) Strengthen both individual muscles as well as combined patterns (free weights, bands, PNF) *core must be strong to function with extremities

Causes of Decrease Muscle Performance

Neurologic Pathology: UMN (central) vs LMN (peripheral) lesions, results in change in msucle tone. Generally, UMN increases muscle tone, LMN decreases muscle tone. Metabolic and Vascular Disease: McArdles, Diabetes, PVD, etc. Injury: muscle strain, inflammation, structural changes to muscle and connective tissue Disuse and Deconditioning: reconditioning up to 2x longer than deconditioning *How does injury affect muscle performance?: must go through healing stages. Guidelines for when to do exercises. You lose what you have way faster than you gain

Recruitment

Number of muscle fibers per motor unit varies significantly. Precision and detail: <10, less complex exercises/large muscles: >thousands. Number of muscle fibers recruited may be increased (causing increased tension) by: activating those motor units containing a greater number of muscle fibers, activating more motor units, increasing the frequency of motor unit activation

Muscle Fiber Types: Type IIB

(fast) Fiber size: 2x as large as Type I Energy Systems: ATP and glycolysis (anaerobic) Mitochondria: less mitochondria Capillary Density: less density Designed For: power

Muscle Fiber Types: Type I

(slow) Fiber size: small Energy Systems: oxidative (aerobic) Mitochondria: greater amount of mitochondria and myoglobin Capillary Density:greater density Designed For: endurance

Stimulus Factors Affecting Muscle Tension: Single Twitch

*Single twitch: stimulus, latent period (stim traveling), contraction, relaxation phase (after peak of contraction) - can get sustained tension.

Muscle Actions

1. Isometric: muscle length doesn't change *Ex: quad set 2. Isotonic: muscle generating same amount of tension at different lengths (concentric, eccentric) *Ex: free weights 3. Isokinetic: speed of contraction doesn't change (concentric, eccentric) *Ex: machines that limit speed

Precautions during resistance training exercise-induced muscle soreness

Acute muscle soreness: develops during or immediately after strenuous exercise performed to the point of exhaustion, due to lack of adequate blood flo wand O2 and temporary build up of metabolites (LA and K) Delayed Onset Muscle Soreness (DOMS): 12-24 hours after exercise Pathological Fractures (OP) *Most recent theory: microtrauma-muscle soreness with exercise, necessary for muscle to rebuild stronger *muscle soreness vs pain Precaution: osteoporosis

Muscle Contraction

All or non principle: In a motor unit, all of the cells that a unit innervates will go at the same time. Impulse from the nerve will innervate all of the fibers in the unit. Contraction occurs at the muscle fiber level within a motor unit. Motor unit: a single motor neuron and all of the fibers it innervates. MUs - generally the same fiber types. Regardless of #, individual muscle fibers within a given motor unit will either fire and contract max. or not at all.

Active and Passive Insufficiency

As muscle shortens its ability to exert force diminishes. Active insufficiency: is reached when the muscle becomes shortened to the point that it can not generate or maintain active tension. (poor lengthening of agonist muscle) Passive insufficiency: is reached when the opposing muscle becomes stretched to the point where it can no longer lengthen and allow movement. Two joint muscles: ex. gastroc being too tight to get full PROM dorsiflexion. (poor lengthening of antagonist muscle)

Stimulus Factors Affecting Muscle Tension

As stimulus strength increases from threshold up to max, more motor units are recruited and overall muscle contraction force increases in a graded fashion. Max stimulus: recruited all of the M.U. in the muscle. No matter how much stim you apply, you can't increase tension. Stim: good for instances where you need to remind nervous system how to use ceratin muscle fibers. Swelling inhibits muscle contraction - stim can override this.

Cardiovascular Adaptions

Associated with resistance exercise Cardiovascular: decreased HR, decreased or unchanged BP, increased or unchanged Q, SV, max O2 consumption, decreased or unchanged total cholesterol, when muscles hypertrophy capillary bed density decreases because of the increase in the number of myofilaments (mitochondrial density decreases, reduced oxidative capacity of tissues, muscles trained for endurance-increased mitochondrial size number, enzymatic activity, and perfusion, improved glycogen storage, use fats over glycogen)

Skeletal Muscle Adaptions

Associated with resistance exercise. Hypertrophy-increase in size of an individual fiber (usually by 4-8 weeks, may be as early as 2 weeks. Associated with high-volume, moderate resistance exercise performed eccentrically. Type II (remember specificity) Hyperplasia-increase in the number of muscle fibers (evidence is sparse) Muscle fiber type adaption: transformation of Type IIB to type IIA (more fatigue resistant) *with patients who aren't athletes, won't see hypertrophy in 2 weeks Moderate resistance > 50% not as scientific because you aren't doing a 1 RM with pts. who aren't healthy

Neural Adaptions

Associated with resistance exercise. Rapid gain in the tension generating capacity of skeletal muscle is largely attributed to neural responses (first 4-8 weeks). Increased recruitment and rate and synchronization of firing. Better recruitment an dcoordination in that time frame. Hypertrophy not usually in 1st 4-8 weeks.

Musculoskeletal Adaptions

Associated with resistance exercise. Tendons, ligaments, and connective tissue: increased tensile strength, associated with eccentric Bone: high correlation btwn muscle strength and level of physical activity with bone mineral density, WB positions recommended, can increase or maintain bone mineral density

Cross Bridge Theory

Attatchment of myosin to actin that results in muscular contraction: Myosin head (S1) is detached from actin and rests in position of 45*. Release of myosin-ATPase allows for the cleaving of a phosphate bond and the release of energy from ATP that has bonded to the myosin head. Energy from ATP re-cocks S1 to 90*. In the presence of Ca2+, troponin and tropomyosin ove to expose the S1 binding site (allows attachment of the myosin head (S1) to the S1 binding site on actin. ADP and Pi are released from S1 which allows S1 to ratchet from 90*-45*. Cross bridge moves which results in tension and sliding between actin and myosin. Ca2+ is removed from the sarcoplasm and a new ATP binds to S1 causing S1 to detach from actin. Hydrolysis of ATP energizes the cross bridge and S1 returns to its resting position of 45*. Tension disappears and the sarcomere returns to its resting length. *cross-bridge originates on thick and terminates on thin *important to have good bond between thick and thin filmaments *Theory: muscle in spasm - Ca2+ can't go back

Psychological Factors

Attention: focus required to learn how to perform it correctly, necessary for safety and optimal long-term training effects *focusing on exercise actually improves recruitment* Motivation: must be willing to put forth and maintain effort, charting improvement may help sustain motivation Feedback: positive feedback can have a positive effect on motivation

Muscle contractions

Cause, control, or prevent joint movement: -initiate or accelerate a movement of a segment (concentric lifting) -prevent movement of a body segment by external forces (shoulder stabilization during biceps curl) -slow down or decelerate movement of body segment (eccentrically lowering weight) -

Progressive resistive exercise (PRE)

DeLorme: overload muscles as they fatigue: 10RM, 10 reps 50% 10RM, 10 reps 75% 10RM, 10 reps 100% 10RM (builds warm up into protocol) Oxford: 10RM, 10 reps 100% 10RM, 10 reps 75% 10RM, 10 reps 50% 10RM (diminishes resistance as muscle fatigues) DAPRE: 10 reps 50% working RM, 6 reps 75% working RM, max reps possible at 100% working RM, max reps possible at 100% adjusted working weight (figure out what working RM is and then you'll use a table to see how to progress) *if you dont see a change in your pt as you're working with them, you may need to alter resistance plan

Plyometric Training

Done for power training, originally developed as "jump" training to develop powerful jumping skills. Three phases: 1. stretch (squat before jump) stretch to get rebound. 2. amortization: middle period (stretch->shortening) 3. shortening: during contraction Tissue must be able to sustain force - not in healing stage. Return to function/chronic stage. Good balance, understand directions, strength and CV good, recovery between training sessions 48-72 hours, 80-85% of strength returned (comp. to other side), 90-95% of ROM needed

Types of resistance exercise: isometric

Duration of muscle activvation: 6-10 sec for strengthening, longer for stability, A 10s contraction allows for a 2s rise, 6s hold, 2s fall Reptitions: use of repetitive contractions decrease muscle cramping Specificity: physiologic overflow is no more than 10degrees in either direction in the ROM from the training angle, therefore perform every 15-20degrees throughout the range, multiple angle isometrics, used when goal is to increase strength throughout ROM when joint angle movement is permissable and dynamic resistance exercise is painful Intensity: <=subgmax for stability and healing tissue, >submax for strengthening *sometimes in acute injury you only do in 1 direction to get the muscle to fire *multiple range isometrics: set at 0, set at 20, set at 40 (degrees flexion) which gives you the overflow of strength each way and you can strengthen throughout range

S/P ankle sprain exercises

Easy->Hard pillow, step up, balance board, theraband, isokinetic machine, ball stabilization

Compare and contrast isometric vs. concentric vs. eccentric in terms of force production.

Eccentric (most tension) > isometric > concentric Can lower more than you can lift due to passive structures. Concentric takes increased energy and fatigues quickly.

Recovery from Exercise

Ex: in between a set, min. should be taken. If a pt. is easily doing something and doesn't need a rest, then exercise needs to be harder becasue they're doing endurance and it's too easy for them. Adequate time for recovery must be built into ever resistance program. 90-95% of recoverly usually takes 3-4 minutes. Greatest amount of recovery occurs in the FIRST MINUTE. Changes that occur in muscle during recovery period: energy stores replenished, LA is removed from muscle and blood within 1 hour after exercise, O2 energy stores replenished, glycogen is replaced over several days. Light exercise performed during recovery period ("active recovery"), recovery from exercise will occur more rapidly than with total rest ("passive recovery"). If a sufficident rest interval is not an integral component of a resistance exercise program patient's performance will plateau or deteriorate.

Overload Principle

For the performance of a muscle to improve, a load that exceeds the muscles metabolic capacity of the muscle must be applied. Reversibility principle: adaptive changes of muscle are transient unless they are maintained Detraining: begins within 1-2 weeks after the cessation of resistance exercise Disuse/immobilization: up to 5% strength loss per day

Sliding Filament Theory

Force is developed by the swiveling of the myosin heads. Actin-myosin cross-bridge must occur to produce tension. If sarcomere isn't at the right length, you either have overlap or no overlap at all and can't produce tension.

Cross Sectional Area

Force is directly proportional to CSA, more CSA = more force How do you increase CSA?: result due to hypertrophy or hyperplasia (biopsy: ripped muscle cells could make it seem like there were more)? When it's safe, overload patients.

Types of resistance exercise: isometric

Improved strength when dynamic exercise not indicated (ie. pain, very weak, acute stage of healing) Minimie atrophy when immobilized Develop postural or joint stability (PNF, alternating isometrics, rhythmic stabilization) Develop static muscle strength necessary for specific tasks

Detrimants of resistance exercise: volume (RxS)

Inverse relationship between volume and intensity Reps: average untrained 75% of 1RM, will be able to complete 10 reps, 60% of 1RM=15 reps, 90% of 1RM=5-4 reps Sets: 1-6 have been shown to be effective Single sets when starting a rogram, but multiple sets have been shone to be superior to single sets

Are muscle contractions in vivo (ie. with changing angles) truly isotonic? Why?

No, because you're changing the moment arm and would need various amounts of effort

Contraindications to Resistance Exercise

Pain (not muscle soreness) Acute inflammation (no strength during acute phase) Severe cardiopulm disease (endurance training more appropriate)

Determinants of resistance exercise: Intensity

Repitition maximum: can be used to calculate a beginning exercise load. 10RM is approx 75% of a 1RM Strength training zone: percentage of RM, usually 70-855 of the RM, used for patients with significant defects for muscular endurance 30-50%, percentage of body weight (i.e. bench press 30%) Trial and Error: in rehab, often we use trial and error in choosing initial weight, then adjust according to the patient's RPE and success of movement, RPE = rate of perceived exertion-patient exercises to a certain % of max based upon subjective feeling Trail and error should still be based on some objective data

Skeletal Muscles

Responsible for active movement Muscle contraction produces force that causes joint movement Muscles also provide: protection, posture/support/stability, produce a major portion of total body heat

Isokinetics

Slow: 30-60 degrees per second Medium: 60-180 degrees per second Fast: 180-360 degrees per second Specificity of isokinetic training, specific speed, therefore velocity spectrum tends to be useful. Faster angular velocities, the compressive forces across the moving joint are less than with slow velocity training. *Slower speeds have higher compressive forces at joint, so higher speeds are better *15degree/second carryover. Velocty spectrum: work at slow -> medium -> fast speeds. Select with each of these multiple speeds because you have small carryover. Ex: train someone at 60degrees/second and you imporoved from 60-45 and 60-75.

SAID Principle

Specific Adaption to Imposed Demands: Specificity of training: adaptive effects of training are highly specific to the training method employed. Ex: whatever exercise you pick, it should be similar as possible to the activity in which you are training. Consider: mode, velocity, position (joint angle), movement pattern Transfer of training: carryover from one variation or exercise or task to another, very limited basics (velocity, mode, Ex: program designed to develop muscle strength has been shown to moderately improve endurance, but endurance training has little effect on strength). In almost all instances the overflow effects are substantially less than the training effects that result from specificity of training. SPECIFICITY TRAINING IS THE BEST*

Examination of Muscle Performance

Tests and measures: analysis of functional muscle strength, power, and/or endurance, MMT, Dynamic strength (repitition max method), dynamometry, Electrophysiologic testing (EMG), Tone/DTRs Magnitude of measured increases in force depends on how similar the test is to the training exercise. Muscle test is only one small part of exam. History, systems review, other tests and measures. *muscle performance according to tension

Eliciting Muscle Contraction

The motor neuron AP causes Ca2+ channels to open (this allows Ca2+ ions to move from extracellular fluid into motor neuron). 1. This triggers excitation-contraction coupling and results in a release of acetycholine (Ach) into synaptic cleft. Ach binds to receptors on the motor end plate. 2. When there is summation of enough miniature end plate potentials an AP is generated (-20mV). 3. AP propagates along the sarcolemma to transverse tubules. 4. Positive charge on the muscle fiber membrane attracts negatively charged electron dense feet, which allows Ca2+ to leak out of the SR (Ca2+ binds to Ca2+ activated Ca2+ channels (CACC) and Ca2+ rushes out of the SR through the CACC).

Dynamic Exercise

Weight machines vs. Free weights Weight machines: constant vs. variable resistance (pulley constant, cam less resistance at beginning and end of motion), advantages (safety, learning curve, efficient set up), disadvantages (expensive, fixed increments, don't fit all body types) Free weights: resistance bands and tubing (benefit of mands over free weights-portable, gravity not as important, home exercise program), advantages (allow for free movement in multiple planes, allow more discrete increases in resistance and difference from R to L, postural muscle stabilization required), disadvantages (injury, learning curve)

Muscle Force - Velocity Relationship

When muscle is contracting (concentrically or eccentrically) the rate of length change is significantly related to the amount of force potential. Concentrically (less tension) < isometric < eccentric (most tensin) but speed does flatten out at a certain point during eccentric