Biomechanics Exam #2

Major tyes of fiber arrangement on phone

parallela and pennate

Damaged Z line, minor trauma

see Z line streaming where the Z line should be clear and tight but see it's torn apart here only in this region. The rest of the muscle is structurally ok. Minor trauma b/c the damage is a stimulus for an increase in muscle force production. So in this case we will see changes in the alpha actinin, stiffness, increase in myofibrils size and will start to increase the % of motor units that are recruited. As you warm up the range of motion increases, so after warm up you don't feel it anymore, so can see diff. In a muscle that has had a minor damage. Amount of force muscle can generate isn't diff. From a regular muscle

static vs. dynamic

statics: study of systems that are in a constant state of motion, wether: -at rest with no motion -or moving at a constant velocity without acceleration Statics involves allforces acting on the body being in balance resulting in the body being in equilibriuum. Dynamics: study of systems in motion with acceleration -a system in acc. is unbalanced due to unequal forces acting on the body.

Active insufficiency AND PASSIVE

when a 2 joint muscle contracts (shortens) across both joints simultaneously By being in a short position. Doesn't matter if it's an active or passive process that got you into that position. Any muscle that is shortened has less force b/c of the thick and thin film. Overlap and the length tens. Relationship. The body will always try to get into a position where you have that optimal overlap. When you are in a shortened bicep position it is easier to extend their arm b/c the sarcomere is only shortened. When you are at a shortened position the sarcomeres are shorter and you get passive tension all the way in the eccentric range as you extend the arm down from the shortened position. That passive tension begins at whatever sarcomere length that muscle is in.

exercise in stress

with training, hopefully, eliciting the apporpriate level and type of stress on physiological systems of th body

EMG testing with visual feedback

-EMG: probes that are attached to electrodes. You can measure elec. Act. of superficial muscles doing surface electromyography (EMG). -Place electrodes on the surface of the muscles superficially. -Did exercises with verbal cuing just as u would get in rehabilitation. Verbal and visual cueing actually. -All found improvement in proprioception and muscle recruitment with visual cueing and an increased antagonist muscle and decrease with antagonist muscle. -Widely used tool in rehab., used with infants as well. Look at reflexes, nerve act., as well as muscle act. -Can get mean and the max EMG and will give u values in millivolts. EMG slide: If we do fast velocity (they show as explosive ballistic) we get an increase of 20% . Green. Slow vel. We get 15% increase from EMG slide So because we get increases in FV and SV the power curve shifts slightly to the R. Slow velocity is pink. 1RM is everywhere on the blue line!!!! We have a maximal velocity at every point on this line that determines what that will be for the 1RM. If we go to a lower velocity than we do have a 2RM and then ultimately we can get down to the point b/c we have a long enough duration that we can have an 8RM. SO 1RM is at the blue point and below is 2RM and below that is 8RM. The difference bet. 1RM 2RM and 8RM is the body's inertia So the orange line is 8RM. Important that it does not start at the blue end point. Limited by fiber type and biochemical properties. And on another pic can now see 8RM moved up because they got stronger so they moved it up. This example is for slow velocity training.

Torque of the human body

-Ex: elbow flexion. Looking at bicep brachii. When angle is greater than 90 deg. Not only do we get a rotational force due to the vertical component or the perp. Component, but we get a joint stabilizing force. That force is coming in towards the elbow joint. Stab. helping to pull that joint together. Vertical component is a rotational component in the case when the angle is greater than 90 deg. In anatomical os. Our elbow is 180 deg. And then when we flex that elbow it becomes a stab. Force then once you get pat 90 deg. That force becomes a dislocating force. Dislocating horizontal force. Bicep itself is trying to pull that elbow apart. PIC ON PHONE: He drew on screen to show angles of bicep curl. -diagram on top R. is individual fibers and each fiber is diff. Length and a pennate muscle. And angles on insertion are diff. ← all how it's supposed to be. Angles of insertion would always be given to us. F sub m stands for the force of the muscle. -angle of penetration depends on the individual muscle or joint position. Ex: this joint angle is 30 deg. So then we have the components of the force both the vertical Fv and horizontal, Fh. Fh ends up being the resultant force vector for the muscle b/c this is the tendinous inscription within the muscle. So looking for the horizontal force. So: Fh = cos30(Fm) Exam question: would be given what the angle of insertion

Agonist

-cause joint motion through a specified plane of motion when contracting concentrically -known as primary or prime movers -some agonist msucle, b/c of their relative location, size, length, or force generatin capacity, are able to contribute significantly more to te joint movement than other agonists. -assisters are agonist

DOMS

-diffuse msucle soreness appearing 48-72 hours after intense exercise -likley due to muscle damage following eccentric muscle action Ex: climbing mt. Whitney, climbing up isn't what makes legs sore, it's climbing down what makes legs sore. Won't feel it when running down a decline b/c having eccentric contractions so that stress is being taken up by the conn. Tiss. by the titin and myosin S1 light chains etc. likely to get this after eccentric muscle action. Also likely to get it after an accustomed exercise.

Directed motion with muscle forces

-in a muscle sys. Like that of a shoulder, multiple muscles exert forces which combine as vectors to produce a net force for directed motion. -force fibers will differ and force vectors within muscles will diff. -when we start to have synergy and have mult. Muscles that are contributing we are looking at the net force vector. Is it retraction? Is it abduction? What is that moment where we have muscle synergies working? -for analysis purposes we look at the resultant force vector. -muscle synergy don't look at the muscles individual forces.

Pennate Muscle and Fiber Arrangement Slide

-in this study they placed surface electrodes along the muscle itself and along the achilles tendon that was superior to the soleus. b/c soleus is a deeper muscle. They put in fine wire electrodes for the gastrocnemius. -measuring muscle activity. Wanted to be looking at the force muscle velocity through high speed synamatix and looking at deg. In penetration with change in joint angle. -subcutaneous layer of adipose and that is not of symmetrical thickness throughout. The point he brings this up is b/c during range of motion there changes in the thickness of the sub. Fat so they measured it at the presidio same location. At the proximal end it is increasing in thickness. During motion we are constantly changing the impedance that we are having so to compare to a fixed joint angle EMG you still have limitations. Good correlation in isometric force. -Proximal fibers shorten to a greater extent than the distal fibers. Prox. angle of pennation increases bsf the greater shortening. -So we don't maintain the same penetration throughout ROM

force vectors with movement

-muscle architecture plays a key role with force/motion dictated by vertical and horizontal components of force vectors, along with lever system, distance of muscle and force application form axis of rotation. -force is dependent upon the axis of rotation and that distance.

musculotendinous strain injury & avulsion fracture

-osteotendinous junction -body of tendon -myotendinous junction -belly (fibers) of muscle osteotendinous junction: -this type of strain is where the bone attaches. The attachment is partially torn in a microstrain. Not completely torn. And these are the locations of strain: -Body of tendon. Myotendinous junction. ← both of these describe the length of tear or partial thickness (only gone far enough with like millimeters or cm) or full thickness (gone entirely through the tendon). -If it's a complete full thickness means they have fully ruptured the tendon at osteotendinous junction or middle of it or myotendinous junction (where endomysium goes into the tendon directly). Avulsion fracture: osteotendinous junction tear. Tendon has been torn off of that bone. Doesn't always mean surgery is required. They will just let that tendon reattach. It will be shorter b/c when a muscle ruptures a tendon it shortens. So we get a reduction in sarcomeres in the series. So could impact the vel. And the power of that muscle, but if it's a small muscle surgeons don't do surgery. Belly (fibers) of the muscle. Any of these strain injuries will create massive inflammation and pain.

The vector sum of two forces

-we have forces that act at right angles. We have that vertical and horizontal force. -in a muscle sys., when the forces act at right angles, the vector sum of any two forces can be obtained geometrically using the pythagorean relationship to find the resultant force. -resultant force follows the pythagorean theorem. Using trig. We can calc. Out any of the vert. Force horiz. Etc. -for forces acting at non-right angles need to use standard trig. To determine the resultant force and angle, alpha, of action. -looking mostly at singing at an angle of force production based upon the tendon insertion.

Eq. that allows someone to calc. Their 1RM.

1RM= weight lifted/1.0278-(0.0278 x # of reps)

Skel. mus. Fiber distribution

95% of fibers have differentiated by 6 years old. In other words an athlete does not train their fibers to be T1, they are born that way and then their training accentuates the properties. Most humans are heterogenous in muscle fiber type so like 50, 50 or slightly more fast twitch. Sarcopenia: not using sarcomeres or those fibers.

Force velocity relationship...F-V relationship and myofibrillar action graph

All diagrams on the slides are in vetro with the muscle taken out of the body. HE DREW GRAPH ON WHITE BOARD PIC ON PHONE. Increase the force in this (newtons) and velocity (%/sec). Po= maximal voluntary isometric contraction (MVIC or Po). At isometric the ext. Torque = the internal torque and that myosin head is staying put. Sedentary person will have a Vmax 300-400%/sec Athletes are 1200%/sec or more. See it goes all the way down to the origin, but this doesn't happen in our body b/c we never have a 0 force or 0mass we are contracting against. So you will decrease but come out at your Vmax. Our muscles have to be moving the mass of the limb we are moving in order to get the move to occur. Inverse relationship bet. Force and Velocity. Like lifting the weights activity we did in class. What dictates: 1. The number of functional cross units. 2. Time with which the cross bridges can form is fewer and fewer the more you increase velocity. Only at the very fast velocities that the very fast T2X fibers are generating force and as you slow the move down more of those fibers can contribute to that force. Therefore, the force goes up as you reduce velocity. Unless you have that cross bridge form you will not generate force. Reason we have a Vmax of avg. individual, a trained ind., and an elite individual b/c we can train. Understand why this grah is in this shae. We experienced it in the lab with the weights. You'll see your results will come out exactly in this curve on the graph. Most find. Don't have proprioceptive control, they can feel their muscles when you put it too light, they only feel it if there is some resistance. MVC: maximal voluntary contractile force. Eccentric contraction you see that myosin head pulls. We are moving the light chains against their conformational chains. If there is a force equivalent to the concentric force you can generate. Natural configuration doing another way makes it harder. That contributes to the eccentric force being greater than the con. Force. It's the myosin head that wants to be going towards the M line but is being pulled towards the Z line. This allows us to generate more force eccentrically. Ex: opening the door in class. In situ means a situation.

Components of passive tension

Alpha Actinin makes up passive tension. Titin is passive only in the fibers that are active b/c the N2A segment attaches to the thin filament. Distropin contributes to the tension. Other things contribute to ALL the fibers, but titin ONLY is passive in active fibers!!! B/c of passive components we can do work.

Effects of fast and slow velocity training on muscle dynamics

As we increase the duration of contraction we are slowing the velocity down. So as we move towards the origin we are increasing the muscular contraction speed. In this study they looked at untrained subjects which are the solid blue line. Max. RFD= maximal rate of force development. With heavy resistance training, which is what we would describe as slow velocity training b/c only at low velocity is the load high. See that Vmax is not changing and that we don't have an increase in force dev. At these faster velocities and then we start to see an increase in slow velocity. Then they did another group and exp. With explosive ballistic training which is fast velocity training. Can see that the entire curve changes and an increase in max force rate of dev. So there can be an increase in the Vmax. Explosive period of the game is most critical for scoring. Muscles here are contractions like crazy here. This is where we need the explosive power. By necessity these athletes have to do slow velocity training if they need explosive power. Fast velocity training: it's the velocity that limits the load. When you see an increase in force production it doesn't mean that you have an increase in cross sectional area, but in vetro you do. Velocity and resistance is slow if in rehabilitation b/c trying to strengthen without damage. Only T1 is recruited at dot on graph b/c not at the rep max. If recruiting all the fibers you don't get sarcopenia.

Force velocity demonstration of raw emg data slide

Can see that eccentricity is much lower. For 5 lb The metabolic requirement is less, not the force for 5 lb Looking at the 25 lb bicep curl pic: can see that the force is greater, but cant say this amp. Equates to 25 lbs. 5lbs at bottom: see amp. Is much greater in this bottom graph on slide. Told to relax on the way down. Much lower amp. In eccentric range than with the sower velocity. We take this raw data and rectify it.

Types of muscle action

Concentric: muscle active while shortening, reduction in joint angle. Always reducing the joint angle. Isometric: muscle active while maintaining constant length, no change in joint angle. Muscle remains at the same length while there is no change in the joint angle. Eccentric: muscle active while lengthening, increase in joint angle with movement slower than gravity or momentum would have limb (overall mass) move. When muscle is lengthening during active tension and increase in joint angle that is resisting either momentum or gravity. Increase in joint angle. Moving slower than gravity. A concentric contraction is when the internal torque being generated by the muscle exceeds the external torque. You are generating more force internally then the external torque created by the limb itself and any external load and there is a reduction in joint angle Isometric contraction internal torque and external torque is equal Eccentric internal torque is less than the external torque.

Dystrophin function

DIAGRAM ON SLIDES oN PHONE N2A segment attaches to the thin filament Titin is a passive protein

Slow velocity training

Ex: elbow flexion with a barbell, like bicep curls. Can do 100 lbs on a barbell. 100 lbs in one rep. SO you would pick 8RM (which is 80%v on the chart on slide) so can do 8 reps with 80 lbs. And can not do that fast b/c that's SV 8RM....for SV strength training. SO 1 SV RM= 100lbs for this situation so means the 8SV RM= 80 lbs. SO 8FV RM= 80 x .2-.4)= 16-32 lbs. .2 and .4 b/c converted to decimal.

if a subject's EMG has been normalized, which do you see the greatest force lifted?

Ex: if someone had normalized data at two diff. % at a given load. As velocity goes up, higher value becomes the higher velocity.

Muscle twitch contraction duration for muscle fiber types

Fast twitch 40 milliseconds for contraction time Slow switch is 200 milliseconds for contraction time. 200 is the longest number.

Shape of muscles and fiber arrangement

Fibers shape and arrangement dictates the amount of force production and rate of force development. Affects the torque. Effects range through which muscle can effectively exert force onto the bones. effects ate of force dev.

FV, force velocity training

For FV training: the velocity is important, not the load!!!! Ex: elbow flexion with a barbell, like bicep curls. Can do 100 lbs on a barbell. 100 lbs in one rep. SO you would pick 8RM (which is 80%v on the chart on slide) so can do 8 reps with 80 lbs. And can not do that fast b/c that's SV 8RM....for SV strength training. SO 1 SV RM= 100lbs for this situation so means the 8SV RM= 80 lbs. SO 8FV RM= 80 x .2-.4)= 16-32 lbs. .2 and .4 b/c converted to decimal. do the velocity not the load, as long as you are moving the velocity you are recruiting all muscle fibers IF YOU DID FV for all individuals instead of just highly trained individuals....Heavy resistance, slow velocity training is actually better for strength gain. never do FV training with injured peeps

sarcopenia

Give ppl. Exercises that require T2 muscle fibers so they don't get sarcopenia

Force-velocity demonstrations of RAW EMG data

He did this study on his students. Just a bicep curl is what they did on rhythm See if we do a 20 lb bicep curl that is higher than what they did you see the contraction is higher and the duration is longer. B/c it's a heavier load. Subject did 5lb fast velocity 1RM...see the amplitude is close to that of the 25 lb dumbbell.

global max

Highest EMG recorded for that muscle. Units in mV In this slide we tested bicep curl only.

Sarcomeres in series vs. sarcomeres in parallel

If a fiber is twice as large then we have increased the myofilaments that are present. BY increasing the sarcomeres that's how we have hypertrophied that muscle, it has gotten larger. And we know the greater the fiber the greater the force. SO someone with a bigger bicep is going to be able to generate more force. Length is a function of one's stature. When someone gets a cast we cast them in a neutral position b/c we don't want to have sarcomeres added in series on the stretched side and sarc. Removed on the passive side. Series: One on top of the other. Vertical. Parallel: SIde by side. Horizontal. 5 ft and 6 inches person and another person who is 6 ft. and 6 inches and think about how the sarcomeres in series impact the velocity of contraction???

How we can modify this Force velocity relationship, sarcomeres in parallel

If you don't change it from fast to slow (change the fiber properties) then the force will go up and the velocity will go down. You can increase muscle strength without increasing muscle size. You just increase more motor units. We recruit more motor units to lift 5 pound then 10 pound then 15 pound etc. And doing all of these at the same velocity. NOt doing it at such a heavy load that you can't do it at the same velocity.

isometric and isoinertial

Isometric strengthens connective tissue this is why we start with it. Not nearly the amount of strength u get with isoinertial training.

Repetition max: (1RM)

Maximal load that can be lifted/torque generated for one rep. With proper movement execution. You aren't using momentum, not using assisted muscle groups. Only looking at that specific muscle. LOOK AT PICS ON PHONE TO SEE GRAPH FOR WHAT 1 2 3 4 ETC RM LOOKS LIKE!!! Picking a load that isn't at your 1RM, you can do more repetitions of the stars that get closer to the origin. You can't do it at that maximal velocity b/c there is only one repetition that can be at vmax. As you increase in effort you move more towards the origin. 1 RM represents rate of ATP reaction biochemically ATP does not last that long in the muscle. Lasts only 1-2 seconds. That's why it's a one rep max (RM). If you are doing more reps you need more ATP. We have creatine phosphate that allows us to generate more ATP quickly so we can do more reps.

Fast and slow motor units

Motor Neurons are referred to motor units Every fiber integrated in a motor neuron has the same chemical and mechanical properties. All identical. Comparison of force and fatigability of motor units: slow fibers of T1 are slow force, T2A are fatigue resistant and T2X is most force We recruit groups of muscle fibers, not just one. One motor neuron being recruited groups muscle fibers as well.

Muscle fiber recruitment

Motor unit: lower motor neuron and all of the muscle fibers alpha??/ innervates. If you look at a muscle in a vetro outside of the body there is no difference. In strength of male or female muscle. It is purley deep. On cross sec. Area. Smaller muscles generating more torque is when we see heavy weight lifters. A lot to do with muscle contractions and attachments and depends upon motor unit recruitment. Motor units allow us to generate the force required for everything. As we start to do more intense activities we then recruit a greater % We are inhibited from recruiting too great of a % of our motor units b/c we pull the tendons off of the bones. As we increase the amount of tension that is being generated. Stimulus can be greater, but your body limits the amount of force the muscle can generate based on its structure. If we are exposed to a greater force we end up with muscle tears, etc. With light work the number of motor units is lower but they are primarily T1 fibers, as we increase the force required by muscle then we get T1 and T2A and then when its heavier work we recruit T1 T2A and T2X. Even though the T2X fibers are generating the most force you are still recruiting the T1 and T2A fibers. We don't have selective rec. But the T1 fibers are contributing less b/c their cross bridges take longer to form. Rate of cross bridge formation is an active process and the compliance properties of the passive components bc when that muscle is undergoing cross bridge cycling that force prod./mech/ work has to be transduced to the endomysium. Components of muscle help us transduce and bring that force from sarcomere to the sarcolemma and to the membrane/endomysium. Titin is a component that helps transduce. Without titin we would not be able to perform eccentric loading. Alpha action is also contributing. It is stiffer in T2 fibers than in T1 fibers and affects the speed at which that transduced force to the bone. Passive components contribute when the muscle is even shorter.

Types of muscle contractions

Muscle contractions that are actually under tension (actually contracting) Muse is isometric when there is 0 velocity. Preventing motion. Isotonic: concentric and eccentric. We don't stay at consistent tension. We have a resistance to movement. We want to get used to saying isotoner/isoinertial. Not isotonic it's isoinertial: concentric, muscle is shortening and then it's eccentric when we are controlling motion. Increase in joint angle or controlling that motion and resisting gravity to control that mov.

resistance training zone

Once the patient has rehbed the PT's start to work with strengthening programs. So they have a choice where they increase the load or Established for ind. Less than 50 years of age. So ppl. Would get resistance training benefits. See increase in muscle strength and can see that on the effect of fast and slow velocity training on muscle dynamics

morphology and force production, penneform and parallel

Penniform fibers: oblique and short fibers (more muscle fibers per unit area generate greater force. parallel fibers: longer fibers such as fusiform arrangement are better for speed and velocity

Length tension curve

Plateau at the top is the normal resting length. 2.2micron In vitro you are in 2.2 micron Lengthening fiber slightly will increase force. Putting a muscle on "pre-stretch." Then we have the typical ascending and descending limb of the muscle. In skel. Muscle we attempt to say somewhere on the plateau or shortly afterwards When a muscle is shortened you have less potential spaces b/c overlapping thick and thin filaments. No then you have no tension b/c thick fillament is budding up agains the Z line. Length tension can be active or passive. Ex: making a fist with forearm upright is easier than with bent forearm. Stronger with the upright position. The body will always try to get into a position where you have that optimal overlap. When you are in a shortened bicep position it is easier to extend their arm b/c the sarcomere is only shortened. When you are at a shortened position the sarcomeres are shorter and you get passive tension all the way in the eccentric range as you extend the arm down from the shortened position. That passive tension begins at whatever sarcomere length that muscle is in.

force velocity power metabolic relationship

Prim. recruiting type 1 fibers. We recruit all, but mainly T1. Can't control them independent of one another. POWER CURVE IS ON FINAL. LOOK AT SLIDE!!! THINK ABOUT HOW THE METABOLIC PROPERTIES AFFECT THE MECHANICAL PROP. VELOCITY IS INCREASING AND DURATION IS DECREASING AS U GO OUT FROM THE ORIGIN. If u do slow vel. U can only see the slow vel. Adaptation but if you do fast vel. Training you can see all the velocities.

signal processing

RAW EMG blue slide....we see a non symmetrical signal in the top L graph b/c you see the deflection during con. Contraction has saturated this voltage and we don't have neg. Deflection. (the long skinny blue line). This is because we are getting other interference from the electrical signals from wall outlets, radiowaves and all other radioactive. That is occurring in the lab while performing the exp. That's why we have to do signal processing that does high and low filtering that clears the extra electrocat. Out in that signal. You need rectification. This is why we get the data on the right. if we don't do signal processing we can't quantify our data means it was rectified Electromyography slide (EMG): This one has been fully signal processed meaning that we rectified it and high and low waves filtered it.Removed all electrical interference so we see it fully saturated. In the top one you can't see muscle perf. Here b/c there is interference.

Resistance training zone

Region on prev. Graph of force velocity and power curve where we are below a 1RM, although we can determine a 1RM. Assuming the individual is trained. Now looking at muscular adaptation. Eq. that allows someone to calc. Their 1RM. = 1RM= weight lifted/1.0278-(0.0278 x # of reps) Motivation plays a role for their 1RM calculations b/c that will affect how many motor units they are able to recruit. Using a straight bar for dumbbell curls is not mechanically safe. Can calc. A load for an athlete. Chart on slide

Is the fiber recruitment any different than at the top of the blue line compared to the end of the blue line???

Remember it's a 1RM the entire curve. So you are recruiting the amount of fibers you are able to recruit. So when you go to 8RM you have recruited the T1, T2A and T2X. The training affects the greater % offibers than when you go to 8RM and 1RM. Those fibers are forming that cross bridge that determine what that 1RM is.

Isokinetic exercise

Same speed. Speed stays constant and stays the same through the entire range of motion. So if u went back to the force vel. Curve, it would be setting the angular vel. That it has to attain before any resistance has been put on any res. Bar. There are isokinetic machines Advantages: controlled, low risk of injury Disadvantages: soooo expensive Limitations: only 3-4 joints that can be trained with this device.

Excess damage-fiber rupture

Sarcomeres are not present anymore. This is when that tissue becomes scar tissue. Athletes taper before a major athletic event to allow the bodies to repair and that repair is structural in the muscular system.

Skeletal, cardiac, smooth muscle types

Skel: -primarily attached to bones, striated and voluntary Card.: forms walls of heart, striated and involuntary Smooth: located in viscera, in non-striated (smooth) and involuntary.

Coactivation

Skilled performers, however, do not exhibit an absence of contact. More controlled and balanced. This is simultaneous action of both agonists and antagonists. If there is equal force you will have no joint motion. But this does not occur when there is equal force Agonist initiates the movement of that limb, then we have an acceleration phase of the limb, but we need to have a deceleration phase that prevents joint stress. SO we have the antagonist muscle come into play to decelerate that limb. Coactivation might occur, for example, when an unskilled performer is unsure of the necessary muscle recruitment strategy. Those who have better skills will better turn on antagonist muscle to decelerate tht limb and reduce joint stresses. Those that have inefficient biomechanics will be turning those muscles on to a greater extent and a not efficient timing is sequenced. Skilled performers will still undergo coactivation to provide for joint stability. skilled performers do not exhibit an absense in coactivation. more controlle dnad balanced

EMG- normalization

Solution: normalize measurments value against a maximal effort vlaue. divide the submaximal effort value (ex: 50%, 75%...) by the maximal effort value the resultant retio (no units) is the normalized signal making direct comparrison possible. B/c the relationship bet. EMG signal and isotonic/isokinetic contracitons is prob. non-linear, most sources recommend normalizing with the maximal voluntary isometric contraction (MVIC) value: EMG value commonly normalized with MVIC Sometimes it will say it's MVC...So this with untrained individuals vs. untrained peeps. By normalizing the data we are campaigning that to the maximal EKG. Wherever they have the highest EMG activity they would use that as the normalization comparison. Using normalization allows us to find these regions on the curve. Does not allow us to find force or what the relative values are.

Staballization and co-contraction reviewed

Stab: holding a joint in a fixed position. -Ex: arm flying motion. Working chest muscles. Both triceps and biceps are active, but these muscles are stabilizing it b/c there is gross motor movement. But the elbow joint itself is stabilized. -Ex: bench press we have co act. Of elbow ext.and flex. At the ends of each joint. Not stabilizing the joint b/c there is motion involved, if you held arm straight then they would be stabilizing. Co-contraction: -during a normal walking gait, whenever you have initial contact (heel strike), the fractions of the second before the heel contacts the ground, both your knee ext.and knee flex. Are activated, still movement taking place, knee is still expanding to reach ground, but they are eco activated, co contracting, but doing that to support the knee joint. Going through a range of motion. As you increase walking speed, you will have greater duration and greater degree of co activation or co contraction. So you can change the impact you have when the heel strikes the ground. You don't have a stabilizing experience b/c it is constantly changing. Knee angle is changing but getting co activation.

Stabalizer

Surround joint or body part Contract to fixate or stabilize the area to enable another limb or body segment to exert force and move Known as fixators Essential in establishing a relatively firm base for the more distal joints to work from when carrying out movements Ex: bicep curl: muscles of scapula and glenohumeral joint must contract in order to maintain shoulder complex and humerus in a relatively static position so that the elbow flexors can more effectively perform curls. Proximal stability is needed for distal mobility. Important for performance and rehabilitation to focus on stabilizer muscles and understand the role stabilizer muscles have for joint mechanics. Critical for joint mechanics.

muscle function neutralization

The process of cancelling out any secondary movement. Fine tuning a muscle is process of neutralization Ex: plantar flexion. We have numerous muscles that cause plantar flexion like gastroc and soleus. However, we can have changes in that plantar flex. Motion to either inversion or eversion. It will either invert or evert the foot. The eversion action of the second muscle would cancel out, or neutralize, the inversion action of the first muscle. Muscles often perform more than one movement function at a given point. The process of canceling out unwanted secondary movement.

Bicep curl force-velocity demo normalization slide

We can see that the mean value is pos. When we select a heavier load we can still move it at the same beats/min but see we've gone up to 1.3 millivolts. He just provided that so we understand how we can equate force with amplitude with EMG signal. RAW EMG blue slide....we see a non symmetrical signal in the top L graph b/c you see the deflection during con. Contraction has saturated this voltage and we don't have neg. Deflection. (the long skinny blue line). This is because we are getting other interference from the electrical signals from wall outlets, radiowaves and all other radioactive. That is occurring in the lab while performing the exp. That's why we have to do signal processing that does high and low filtering that clears the extra electrocat. Out in that signal. You need rectification. This is why we get the data on the right.

How do you know when you can increase?

When you have proprioception so you can feel when that movement starts to slow down on that 8th rep. (ex.) Could do 12 reps, but just do it slower. 12 rep. Max would be with a lighter weight. Pick up the lightest dumbbell adn do elbow flexion bicep curls,then go to 7.5 and if you do 8 reps you will feel that the 7.5 reps is slower, it has to be b/c of the force velocity curve. Important thing is to do the velocity, not the load. As long as you are moving the velocity at that laid you are recruiting all the fibers.

assisters or assistant movers

agonist muscle that contribute signif. less to the joint motion is an agonist as well, but at optimal length tension when we are in mid position. Agonist muscles that contribute significantly less to the joint motion. Ex: if doing a bicep curl, we know length tens. Relationship is most effective for biceps brachii and least effective for brachialis. When supinated like this bicep curl my primary mover is the bicep brachii and my sisters are the brachioradialis and brachialis.

synergist

assisnt in action of agonists not necessarily prime movers for the action known as guiding muscles assist in refined movement and rule out or limit undesired motions

What load do I select because i cant have an isokinetic machine for every type of exercise???

bet. 20-40% of their slow velocity max. SO FV RM= 20-40% (SV RM).

EMG Have to do signal processing

clears out electrical interference and rectifies the data, changes it from alternating current to direct current.

shape of mus. fiber arrangement: cross section diameteer and muscles ability to shorten

cross section diameter: -factor in muscles ability to exert force -greater cross sec. dia. = greater force exertion -penniform muscles have larger number of fibers, force production potential than longitudinal fiber arrangements. -force production occurs through a smaller range of motion muscles ability to shorten: -longer muslces can shorten through a greater range -more effective in moving joints through large ranges of motion -longitudional fiber arrangements.

Mechanics

divided into static and dynamic study of physical actions of forces

msucle tissue properties

excitibility: ability to respond to stim. by producing AP's Contractillity: ability to ahortena dn thicken, generating force to do work extensibility: abiity to be extended (stretched) w/out damaging tissue elasticity: ability to return to original shape after contraction to extension

rectifying

going from raw data/current to direct current.

Functions of muscle tissue: gross, stability, move., thermo.

gross motion: results from altering contraction (shortening) and relaxation of muscles Stability: stabalizing body ositions Movement: regulating organ or vessel vol, size and movement of contents. Thermoregulation: generation of heat

RM's

limited by fiber type and biochem. properties diff. bet. each RM is inertia You need to do repetition max training. Reps tell you nothing. If there isn't adequate resistance you won't get an adaptation.

antagonist

locate on opposite side of a joint from the agonist have the opp. concentric action known as contralateral muscles work in cooperation with agonist muscles by relaxing and allowing movement when contracting concentrically perform the opposite joint motion agonist ex: quadriceps muscles are antagonists to hamstrings in knee flexion

Muscle tone

muscle fibers never completly relaxed. A little tension is always present, maintaining the shape of the body even though no movement takes place. this partial contraction of muscles is called muscle tone muscle tone is important for maintaining good body posture, placing the minimum amount of stress on the musculo-skeletal system. Some muscles have more tone in them b/c of daily activities. Some ppl. Tend to be more toned in the anterior muscles b/c we tend to do things where we are leaned over, picking up packages, etc. Muscle tone is important for maintaining good body posture, placing the min. Amount of stress on the musculoskeletal shit. Some ppl. Who appears flabby isnt fat, it's just not muscle tone.

muslce power =

muscle power = force x distance/time

gains in fitness

occur during recovery phase provided by adequate and optimal nutrition and rest, not during the training period

Impact of muscle struc. Change on force cap slide

on phone sin cos tan