Joseph Langmeyer, Age 7, grabbing some air. Physiology at it’s finest!

CHAPTER 2

EXERCISE PHYSIOLOGY

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Exercise physiology is the study of the cellular functions in the human body during and afterexercise. This chapter was designed to educate you on the basic principles and applications of exercisephysiology so you can apply this knowledge in working with your clients.

Each human body has the same organs, hormones, blood and enzymes as the next human body. Howthese components interact with each other is unique with each individual. This is why it is important tounderstand the basic principles of exercise physiology in order to maximize each client’s potential.

Think of it this way. Each person has been dealt a “hand” to play with. Some of us are blessed withgood genes, or a “full house” and can get away with eating anything we want. Some of us would like totrade in for some new cards. It is your job as a personal trainer to find a solution to your client’s fitnessproblems.

The basic unit of life, energy, is expressed in the body as ATP (Adenosine Triphosphate). There arethree energy systems in the human body to produce adenosine triphosphate (ATP). ATP is the currency or“pocket change” your body will use to pay for “work” performed in the body. The breakdown of this high-energy molecule ATP, into adenosine diphosphate (ADP) and inorganic phosphate (Pi), fuel thecontraction of skeletal muscle. The formula is: ATP~~~ADP + Pi = ENERGY.

THE THREE ENERGY SYSTEMS

The three energy systems are the ATP/Creatine–Phosphate system (The phosphagen system),Glycolysis (Anaerobic, glycolytic system), and Aerobic Oxidation. The purpose for any of these systemsis to phosphorylate ADP to produce ATP. The ATP/Creatine–Phosphate system and Glycolysis areconsidered a n a e ro b i c, which means these systems do not require oxygen to function. T h eATP/Creatine–Phosphate system is the body’s immediate energy system used during physical work thatlasts 1–10 seconds. When immediate energy is needed for rapid, high-intensity activities, the body breaksdown the ATP to fuel about one second of explosive exercise. As a result, ATP must be continuouslyresynthesized and replenished to meet the body’s needs. One way the body accomplishes this is whenanother high-energy compound, Creatine–Phosphate (CP), located in the muscle cells in limitedamounts, can combine with adenosine diphosphate (ADP) and is used immediately to replenish ATPstores. Because the body’s cells can store about four to six times more CP than ATP, CP is the predominantsource of immediate energy.(12) The primary use for this energy system is high intensity effort such asweight lifting, sprints, and tennis.

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Example of Anaerobic Exercise:

When exercise lasts longer than 10 seconds the Glycolytic system kicks in to provide ATP. Glycolysisor the Glycolytic system is the breakdown of carbohydrate to pyruvate or lactate to generate ATP.Glycolysis can last from 10 seconds to three minutes and is characterized by the lactate production inmuscles commonly mistaken for lactic acid or the “burn.” Note the use of the term “lactate” rather than“lactic acid.” When produced at physiologic pH, (the measure of the acidity of a solution) lactic acidimmediately releases a proton also called a hydrogen ion (H+), and thus exists as the molecule lactate.Although Glycolysis is an anaerobic process, in that it does not directly use oxygen, this should not beinterpeted to mean that Glycolysis occurs only in the absence of oxygen. In actuality, Glycolysis occurswhether oxygen is present or not, and it’s end-product pyruvate, is the first step in the aerobic breakdownof carbohydrate. The end-product of Glycolysis is either pyruvate or lactate depending on a few factorssuch as oxygen availability and the energy demands of the particular activity. This is very important.When the demand for oxygen is greater than the supply, pyruvate is converted to lactate. If there is enoughoxygen available, lactate is not formed and pyruvate enters the mitochondria becoming the first step inthe aerobic degradation of carbohydrates; thus, it is sometimes referred to as “aerobic” or “slow”glycolysis. Lactate may also be used as a source of energy, be converted back into glycogen by thereversal of the reactions of Glycolysis, or be used by the liver to make new glucose by a process calledgluconeogenesis. Thus, lactate is far from being a waste product. If oxygen is not available (anaerobicexercise), there is an accumulation of H+ in the muscle and body fluids. While the accumulation of H+in the muscle increases the muscle’s acidity (lowers the pH), lactate has traditionally been the culpritblamed for fatigue. The problem with lactate is the accompanying acidosis, not the lactate molecule itself.It is the accumulation of the H+, rather than the lactate molecule that causes muscle acidosis and theensuing quick fatigue or “burn”, and tetanus will occur. H+ is also produced from the breakdown of ATPduring muscle contractions, as well as from other chemical reactions of Glycolysis. It is important tounderstand that lactate does not cause fatigue; an increase in H+ concentration does. The suddenaccumulation or rise in lactate is called Lactate Threshold or Onset of Blood Lactate Accumulation(OBLA).

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PHOSPHAGEN ANAEROBIC AEROBIC OXIDATIONSYSTEM GLYCOLYTIC SYSTEM SYSTEM

METHOD OFENERGY PRODUCTION ANAEROBIC ANAEROBIC AEROBICfuel source primarily CP carbohydrate carbohydrate, fat, proteinduration < 10 seconds 10 seconds to 3 minutes > 3 minutesintensity very high to high to moderate moderate to low

high intensity; intensity; intensity;95%-100% of maximal effort 85%-95% of maximal effort <85% of maximal effort

examples of < 100 m sprint, 400 to 800 m run, > 1,500 m run, > 3,000 m cycling,events power lifting 50 m swim > 400 m swimoxygen involved no no yes

*Mitochondrial respiration involves the continued oxidation of carbohydrates that were originally broken down to pyruvate during “aerobic” glycolysis, as well as the aerobic breakdown of lipids and amino acids.

Energy Systems at a Glance

How DifferentNutrients Fuel

Exercise atDifferent

Intensities

LIGHT- TO MODERATE- HIGH-INTENSITY HIGH-INTENSITYNUTRIENT AT REST INTENSITY EXERCISE ENDURANCE EXERCISE SPRINT-TYPE EXERCISE

protein 2%-5% 2%-5% 5%-8% 2%carbohydrate 35% 40% 70% 95%

fat 60% 55% 15% 3%Source: Adapted from McArdle, W.D., et al, 1999. Sports & Exercise Nutrition. New York: Lippincott Williams & Wilkins.

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The main source of anaerobic ATP production is glucose, which is stored in muscles and the liver asglycogen. The buildup of anaerobic ATP production waste is lactic acid. As lactic acid levels rise in themuscles, fatigue sets in quickly.

The aerobic pathway to produce ATP is called Aerobic Oxidation or the Mitochondrial RespirationSystem, which is the catabolism of glucose and fatty acids by way of the Kreb’s Cycle and ElectronTransport System in the mitochondria of the cells. The Kreb’s Cycle is a metabolic process in whichhydrogens are removed from four molecules in a circular fashion, starting from pyruvate degraded toacetyl-CoA. The electrons from these hydrogens then follow an electron transport system and theenergy released from this process is used to phosphorylate ADP to ATP. Oxygen accepts the hydrogensfrom the Kreb’s Cycle to form H2O.

Although aerobic and anaerobic exercise is clearly defined, in actuality, the energy to perform exerciseis a combination of both systems. The use of anaerobic sources for energy metabolism is inversely relatedto the duration and intensity of the activity. The harder and shorter the activity, the greater the contributionof anaerobic energy production. As exercise progresses over 20 minutes, a greater percentage of energyshifts from carbohydrate metabolism to fat metabolism.

MUSCLE PHYSIOLOGY

The human body uses skeletal muscle for movement. Muscles can be defined collectively as musculartissue, nerves, connective tissue and blood vessels. There are two components of muscles that define itsmovement properties. An active contractile component that produces tension through the siding ofmicroscopic fibers, which shortens muscles, and a passive non-contractile component that consists oftendons, connective tissue and ligaments. There are three types of connective tissue that encompassesmuscles. At the smallest level surrounding the muscle fiber is a connective sheath called thee n d o m y s i u m. This sheath serves toelectrically insulate the muscle fiber fromother muscle fibers and is associated withthe muscle fiber cell membrane, thesarcolemma. This enables each musclefiber to be actively stimulated withoutstimulating neighboring fibers. Groups ofmuscle fibers (up to 150) are sheathedtogether into bundles called f a s c i c u l i.These fasciculi bundles are surrounded bythe connective tissue sheath called thep e r i m y s i u m. This p e r i m y s i u m i scontinuous with the tendon. All of thefasciculi in a particular muscle make upthe complete muscle as we see it. Theentire muscle belly is wrapped together bythe connective tissue sheath called thee p i m y s i u m. This e p i m y s i u m is whatdesignates how the muscle is shaped. Aswith the perimysium, the epimysium isalso continuous with the tendon. Eachm u s c l e ’s tendon attaches to theperiosteum, a connective tissue coveringbone.

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Structure of skeletal muscle

Muscles are parallel multi-nucleated cells attached to the skeletal system. Each skeletal muscle fibercontains hundreds to thousands of myofibrillae that contain the contractile properties of the muscle cell.A myofibril is the smallest unit of a muscle cell and is composed of two myofilaments. A thick filamentthat contains the protein myosin, and a thin filament that contains the protein actin.

Myosin thick filaments

A myosin filament is made up of hundreds of myosin molecules attached together. These myosinmolecules look like miniature two-headed golf clubs. The “golf club heads” are referred to ascrossbridges. It is only the crossbridges that are able to move while the other sections remains stationary.The head moves back and forth and is the driving force for muscular contraction. The tail of the myosinmolecule, or golf club handle has a movable section that allows the crossbridge to bind with the actin thinfilament. Upon binding, this hinge moves the actin molecules with the myosin molecules implementingcontraction. This movement or “golf club swing,” constitutes the full power stroke and function of theglobular myosin heads. The two heads of the myosin molecule (crossbridge) each have a characteristicbinding site. One head binds with the energy molecule adenosine triphosphate (ATP). When thisbinding site with ATP is open, the second crossbridge is still connected to the actin molecule afterfinishing its power stroke. This position is called a low-energy conformation. When an ATP moleculebinds to the crossbridge, it disengages the second crossbridge from the actin molecule. At this point, theATP is hydrolyzed into adenosine diphosphate (ADP) and inorganic phosphate (Pi) releasing its energyto the second crossbridge causing it to revert back to its original position. This position is called the high-energy conformation. It is now ready to pull the actin molecules and implement contraction. Upondisengaging from the second crossbridge the actin molecule now has an active binding site ready to bind.The myosin molecule’s second binding site is built for binding to the active site on the actin molecule.The globular heads of the myosin molecules form a crossbridge with the actin molecules in the presenceof the ATP and Calcium.

Actin Thin Filaments

The actin thin filament is made up of three protein molecules that include actin, tropomyosin andtroponin. These three actin molecules are strung together like a pearl necklace. The tropomyosinmolecule’s function is to cover the actin binding sites when the muscle is not stimulated. When a muscleis stimulated, tropomyosin gets off the actin molecule so the myosin molecule can bind to the actin activesite. The globular protein molecule troponin is configured with the tropomyosin molecule and is boundto it temporarily, when the nervous system stimulates calcium to bind to the troponin molecule.

MUSCLE FIBER TYPES

There are three types of muscle tissues: Skeletal, cardiac and visceral.Skeletal muscle tissue or striated muscles are attached by tendons and are commonly named

according to their location. These are the muscles operate your skeleton and become stronger and thickerwhen you weight train.

In skeletal muscle there are two main types of muscle fibers, Slow Twitch and Fast Twitch. SlowTwitch fibers (also called Type I), are oxidative fibers. These fibers are fatigue resistant and have a lowglycolytic capacity. They are rich in capillarie and myoglobin, which enhances oxygen delivery. Musclesthat contain a lot of slow-twitch fibers are red because they contain lots of blood vessels. They also havean increased number of mitochondria which enhances their ability to oxidize fats. Fast Twitch fibers (alsocalled Type II), are divided into Type IIa and Type IIb based on their oxidative capacities and velocity ofcontractions. Fast-twitch muscle fibers don’t use oxygen to make energy, so they don’t need such a richblood supply. Type IIb fibers appear lighter in color than muscles that contain a lot of slow-twitch muscles

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and are referred to as white muscle fibers while Type IIa a referred to a pink muscle fibers. Type IIa fibershave moderate glycolytic and high oxidative capacities. Type IIb fibers have high glycolytic and lowoxidative capacities. Type IIb are larger and are well suited for brief powerful contractions. Type II fibersare recruited at a higher percentage of maximum force than Type I fibers. A normal individual might have52% Type I, 30% Type IIa, and 12% Type IIb.

Cardiac muscles are made up of the myocardium. Visceral or smooth muscles operate blood vesselsand tubular organs such as the stomach and uterus. They are also found around the walls of blood vesselsand bowels. Smooth muscle gets it name because there are no striations visible in them. Smooth muscleis autonomous or doesn’t require conscious thought to be stimulated. The fibers consist of bundles thatare closely connected by junctions which allow ions to flow freely between these bundles. If one sectionof the smooth muscle is stimulated the action is distributed to all the other fibers.

CLASSIFICATION OF MUSCLES

Each muscle can be named according by shape (deltoid), location (biceps femoris), or by acombination of location and function (extensor digitorum longus). Muscles can also be named on thebasis of the actions they perform or the role they play in a specific movement. When determining whichmuscles are involved in an exercise, it helps to know the origin and the insertion of each muscle. Theorigin of a muscle is the attachment nearest the midline of the body and/or the end attached to the leastmovable bone.

Muscles that cause flexion at a joint are called Flexors. Muscles that cause extension at a joint arecalled Extensors. Muscles that cause rotation at a joint are called Rotators. A muscle that is responsiblefor causing a desired motion at a joint is called a prime mover, or Agonist. The muscles that directlyoppose the desired motion are called Antagonists. The muscles that assist the Agonist to perform adesired motion are called Synergists. The muscles that contract isometrically at a joint but do notcontribute to the movement are called Stabilizers. When an agonist or prime mover is called upon toperform a desired motion, the antagonists are neurologically inhibited. This is called “Sherrington's lawof reciprocal innervation*,” which states that for every neural activation of a muscle, there is acorresponding inhibition of the opposing muscle. This phenomenon occurs to increase force productionfor the a g o n i s t by decreasing opposing forces. When the a g o n i s t and the antagonist contractsimultaneously, this is called Co-contraction, or an isometric contraction. Co-contraction provides jointstability or can create synergy of the muscles to complete the desired motion.

SPURT AND SHUNT MUSCLES

Spurt muscles are muscles that have their distal tendon close to the joint axis, as in the biceps brachii.They have a major rotary component. Shunt muscles are muscles that have their distal tendon far fromthe joint axis. They usually act as joint stabilizers. When muscle action is reversed, as in performing apull-up followed after a curl, the biceps role switches from spurt to shunt. Basically, when the musclecrosses the joint it is moving it could be considered a spurt, but when the muscle lies against the bone itis moving it could be considered a shunt.

TONIC AND PHASIC MUSCULATURE

The tendency of some muscles tend to become tight and others weak has long been observed in bothneurological (i.e. cerebral palsy, stroke) and orthopedic (i.e. nerve root compression) problems. Rood was

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*Sir Charles Scott Sherrington (27 November 1857 – 4 March 1952) was a British scientist known for his contributions tophysiology and neuroscience. He shared the 1932 Nobel Prize in Physiology or Medicine with Edgar Douglas Adrian for theirdiscoveries regarding the functions of neurons.

one of the first to propose classifying muscles on the basis of their functional characteristics as stabilizersor mobilizers. Janda and Sahrmann have championed this way of thinking which finally came underscientific scrutiny with Bergmark who proposed that muscles could be broadly classified as deep, localstabilization muscles or superficial, global mobilization muscles.

Janda has suggested that there is a group of postural muscles (i.e. gastrocnemius, upper trapezius,SCM, erector spinae) that are involved in static tasks such as standing or sitting. These muscles have atendency to become overactive. He describes another group as phasic because they are involved instabilizing or producing dynamic movements such as head flexion, arm elevation or trunk curling (i.e.deep neck flexors, inferior scapular fixators, and abdominals). These muscles have a tendency to becomeinhibited. This notion emerged from his observation amongst individuals with neurological disease thatspasticity (e.g. cerebral palsy) usually favored certain muscles (i.e. extremity flexors, adductors andinternal rotators) and paralysis (e.g. stroke) other muscles (i.e. extremity extensors, abductors and externalrotators). Janda described how the postural muscle system was needed for preservation of basic functionsand its muscles were usually spared while those required for more dynamic activities were more fragileand easily compromised. He also noted that these same tendencies were seen in individuals withoutneurological disease, who either remained in constrained, sitting postures for prolonged periods of timeor were training their muscles inappropriately.

This theory has a neuro-developmental basis. In the young infant (under 1 month old) the fetalposition is maintained by tonic contraction of trunk and extremity flexors along with extremity adductorsand internal rotators. Reciprocal inhibition, (Sherrington’s law) which is present in early infancy inhibitsthe antagonists of the tonic muscle chains. As the infant develops, reciprocal inhibition dampens, thusallowing the phasic muscle system to activate. As the reflex bound infant begins to develop its posturalcontrol system, the tonic activity of muscles which maintains the fetal posture is superseded by agonist-antagonist co-activation of muscles necessary for movement control and production of the uprightposture. Thus, extensors, abductors, and external rotators co-activate with their fetal partners to stabilizejoints and allow neurodevelopment of posture.

For instance, orientation movements of the head and neck begin between 4 and 6 weeks as the deepcervical flexors activate to coordinate movement with the cervical extensors. Similarly, the inferiorscapular fixators begin to activate in the following months to balance the activity of the upper trapeziusand levator scapulae and allow for scapulo-thoracic stabilization during arm movements (grasping,prehension, pushing, pulling, etc.).

Tonic muscles are easily facilitated and will want to contribute to the movement with low levels ofinnervation. They are characterized by having a high proportion of slow twitch fibers, penniformtype arrangement, are deep and cross one joint. However, there are some exceptions, such as the rectusfemoris. Their main function is for joint stability. Since they have a tendency to be tight it’s important tokeep that in mind when designing a training program. If you find tightness in these muscles when youperform your first assessment then take care to strengthen the antagonists to rob the agonist of the neuralinput. Remember, these muscles will “play” or contribute with low levels of innervation. Some examplesof tonic muscles are listed below.

Phasic muscles on the other hand have a tendency to become inhibited. They are characterized byhaving a high proportion of fast twitch fibers, parallel type arrangement, are superficial and cross morethan one joint. There are also some exceptions such as the gluteus medius. Their main function ismobility.

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If you discover these muscles to be long and weak then make sure you stretch the antagonist firstbefore you strengthen or activate the phasic muscles you’re targeting. Some examples of phasic musclesare listed below.

Phasic muscles are either “on” or “off” as opposed to tonic muscle which are constantly “on.”

ACTIVE AND PASSIVEINSUFFICIENCY

There are certain musclesin the body that cross twojoints and are able to producemotion at more than onejoint. These muscles arecalled two-jointed muscles.Although these muscles canbe very helpful in moving thebody more efficiently, theyare more susceptible todevelopments called active and passiveinsufficiency.

Active insufficiency occurs when adouble-jointed muscle is recruited towork at both joints causing an over-shortening of the muscle. An examplewould be to flex the wrist and flex thefingers at the same time. A sufficientcontraction cannot occur because thefinger flexors are shortened over both theflexed wrist and fingers.

Passive insufficiency occurs when an inactive muscle at a joint is of insufficient length to permit fullrange of motion. An example would be the same example above except note that the finger extensors arelengthened over both the wrist and fingers andare preventing full range of motion to becompleted.

TYPES OF MUSCULAR CONTRACTIONS

The three types of muscular contractions areC o n c e n t r i c, E c c e n t r i c and I s o m e t r i c.Concentric contraction is the shortening of themuscle fibers. E c c e n t r i c contraction is thelengthening of muscle fibers. Isometriccontraction is the contraction of the musclefibers with no visual movement occurring.

Although an Eccentric contraction is thestrongest of the three, it also is responsible for

Example of Anaerobic Exercise:

Postural and Phasic Muscles (11) Postural (Tend to hyperactivity) Phasic (Tend to hypoactivity) Triceps surae — H Tibialis anterior — NAdductors — D Gluteus maximus — QRectus femoris (at the hip) — C Gluteus medius — STensor fascia latae (TFL) — B Lower/middle trapezius — TPsoas — E Longus capitus & colli — JErector spinae Deltoids — KQuadratus lumborum (QL) DigastricsPectoralis Major — F Biceps brachii — LUpper trapezius — A Triceps brachii — PSternocleidomastoid (SCM) — G Vastus medialis — MSuboccipital — I Rectus abdominis — ODeep abdominals Hamstrings (At the knee) — R

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Postural Muscles Postural Muscles Phasic Muscles Phasic Muscles

micro-trauma to the muscle tissue resulting in Delayed Onset Muscle Soreness, (DOMS). The secondstrongest contraction is Isometric, and lastly Concentric.

When a myofiber is innervated by a nerve cell, it contracts totally or not at all. This is called the Allor None Principle. When an action potential is sent down a nerve cell all of the muscles fibers that thenerve connects to will be stimulated to contract evenly and simultaneously. Each myofiber is innervatedby a nerve cell. A motor neuron and the muscle fibers it innervates are called a motor unit.

A motor unit is a single -motor neuron and all of the corresponding muscle fibers it innervates.Groups of motor units often work together to coordinate the contractions of a single muscle; all of themotor units that subserve a single muscle are considered a motor unit pool. The number of muscle fiberswithin each unit can vary: thigh muscles can have a thousand fibers in each unit, eye muscles might haveten. In general, the number of muscle fibers innervated by a motor unit is a function of a muscle's needfor refined motion. Muscles requiring more refined motion are innervated by motor units that synapsewith fewer muscle fibers.

Alpha motor neurons are large lower motor neurons of the brainstem and spinal cord. Theyinnervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating theircontraction. Alpha motor neurons are distinct from gamma motor neurons, which innervate intrafusalmuscle fibers of muscle spindles.

While their cell bodies are found in the central nervous system (CNS), alpha motor neurons are alsoconsidered part of the somatic nervous system—a branch of the peripheral nervous system (PNS)—because their axons extend into the periphery to innervate skeletal muscles.

An alpha motor neuron and the muscle fibers it innervates is a motor unit. A motor neuron poolcontains all the alpha motor neurons involved in contracting a single muscle as opposed to gamma motorneurons which are slow-conducting lower motor neurons that innervate intrafusal muscle fibers. Theyform part of the reflex circuit that underlies muscle spindles and are therefore an integral part of the senseof body position.

Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons. Contractionof these fibers generates mechanical work and allows for movement. Extrafusal muscle fibers andassociated alpha motor neurons are called a motor unit. The connection between alpha motor neuron andextrafusal muscle fiber is a neuromuscular junction

Intrafusal fibers are muscle fibers that comprise the muscle spindle. These fibers are walled off fromthe rest of the muscle by a collagen sheath. This sheath has a spindle or “fusiform” shape, hence the name“intrafusal.” While the intrafusal fibers are wrapped with sensory receptors, their counterpart, extrafusalmuscle fibers are the ones responsible for the power-generating component of muscle and are innervatedby motor neurons.

The first of the two main group of stretch receptors wrapping the intrafusal fibers are the Ia fiber,which are the largest and fastest fibers, and they fire when the muscle is stretching. They are characterizedby their rapid adaptation, because as soon as the muscle stops changing length, the Ia stop firing and adaptto the new length. Ia fibers essentially supply proprioceptive information about the rate of change of itsrespective muscle: the derivative of the muscle’s length (or position).

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The second of the two main groups of stretch receptors are the II fibers, and they are non-adapting,meaning that they keep responding even when the muscle has stopped changing its length. Their firingrate is directly related to the muscle’s instantaneous length, or position. This information would indicatethe position of one’s leg once it has stopped moving.

It is by the sensory information from these two intrafusal fiber types that one is able to judge theposition of their muscle, and the rate at which it is changing.

In the nervous system, afferent neurons—otherwise known as sensory or receptor neurons—carrynerve impulses from receptors or sense organs toward the central nervous system. This term can also beused to describe relative connections between structures. A ff e rent neuro n s communicate withspecialized interneurons. The opposite activity of direction or flow is efferent.

In the nervous system, efferent nerves—otherwise known as motor or effector neurons—carry nerveimpulses away from the central nervous system to effectors such as muscles or glands (and also theciliated cells of the inner ear). The term can also be used to describe relative connections between nervousstructures. The opposite activity of direction or flow is afferent.

The motor nerves are efferent nerves involved in muscular control. The cell body of the efferentneuron is found in the central nervous system where it is connected to a single, long axon and severalshort dendrites projecting out of the cell body itself. This axon then forms a neuromuscular junction withthe effectors. The cell body of the motor neuron is satellite-shaped. The motor neuron is present in thegrey matter of the spinal cord and medulla oblongata, and forms an electrochemical pathway to theeffector organ or muscle.

The mechanism of how a muscle contraction occurs is called the Sliding Filament Theory. The twomain proteins in a muscle cell, actin and myosin, interact by sliding across each other at the expense ofATP. For this to happen it must receive a signal from the central nervous system.

Law of Facilitation: When an impulse passes once through a given set of neurons to the exclusionof others, it will tend to do so again, and each time it transverses this path, the resistance will be smaller.

Facilitation is defined as the enhancement or reinforcement of a reflex or other nervous systemactivity by the arrival of other nervous activity at the reflex center of other excitatory impulses.Remember, perfect practice makes perfect performance!

Size Principle of Recruitment

This principle states that selection of motor neuron size and the muscle fibers it innervates follow anorder of efficiency, from smallest to largest. Generally speaking, motor units containing smaller motorneurons and slow-twitch muscle fibers are recruited first, followed by increasingly larger motor neuronsconsisting of either the fast-twitch fibers Type IIa or IIb.

Graduation of Response

Graduation of response is the process by which the central nervous system determines the number andtypes of motor units recruited as well as the number of times they fire, causing appropriate responses,relative to the degree(s) of muscle force required.

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BODY COMPOSITION

Body-fat norms for men and women are different. Women carry about seven percent more body-fatthan their male counterparts due to the energy needed for the development of the fetus. A persons gender,body type, age and activity levels can determine how an individual’s .subcutaneous fat levels aredistributed. Females typically store fat in the triceps, thighs and hips, while men store it in their abdomen.While there are no universal body fat standards, it is generally accepted that essential fat makes up 3-5%of total body fat in men and 8–12% in women.

The American College of Sports Medicine (ACSM) has defined obesity as a body fat percentageof over 25% for males and over 32% for females. ACSM considers a healthy body fat range for menbetween 8–22% and for women, 20–35%. This author (me) finds this ridiculous. If obesity is defined as25% for males and 32% for females, why would an organization with the name medicine regard apercentage almost equal to, or higher than obesity as healthy? We at the NCCPT recommend 10–15% formen and 15–20% for females as healthy range. Think of it this way. If the percentage for obesity wasgraded as an “F” and “A” was graded for the percentage for essential fat then a “C” would fall in themiddle. This would equate to 12% for men and 19% for women. I believe everyone should at least shootfor a grade of C when it comes to their health, don’t you?

Hormonal Responses to Resistance Exercise

Hormones are chemical messengers that are stored, created and released by the endocrine glands.Similarly, neurons synthesize, store and secrete neurotransmitters which may also have hormonalfunctions. Hormones regulate nearly all our bodily functions. They regulate growth, development, helpus cope with both physical and mental stress and regulate all forms of training responses including proteinmetabolism, fat mobilization and energy production.

Resistance training is a natural stimulus that can cause an increase in tissue mass. Dramaticdifferences exist among resistance training programs in the ability to produce increases in muscle andconnective tissue. These adaptations are influenced by the changes in circulating hormonal concentrationsas a result of exercise.

Testosterone

In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females,although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone andan anabolic steroid. In men, testosterone plays a key role in health and well-being as well as preventingosteoporosis. On average, an adult human male body produces about forty to sixty times moretestosterone than an adult human female body, but females are, from a behavioral perspective (rather thanfrom an anatomical or biological perspective), more sensitive to the hormone.

Not all exercise protocols may elicit increases in the circulating concentrations of hormones in thebody. Significant amount of force is required to activate high-threshold motor units not typicallystimulated by endurance exercise. Keep in mind however, high-intensity endurance exercise can have avery dramatic catabolic effect and in increase in testosterone may increase to maintain protein synthesisto keep up with protein break-down. Following the exercise session, remodeling of the muscle tissuebegins in the environment of hormonal secretions stimulating and anabolic action.

The primary anabolic hormones involved in muscle tissue growth and repair are testosterone, growth

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hormone and insulin-like growth factors (IGF). Some studies show that certain exercises or combinationsof several exercises such as dead-lift, power clean and squats have shown to increase serum testosteroneconcentrations. The resistance was 85–95% of 1RM (repetition maximum), with multiple sets of 5–10reps and short rest intervals of under one minute.

Training experience and age of the participants also affects testosterone. A study has shown that anincrease may occur if the resistance training experience is two years or more with high school-aged malesof 14–18 years of age. Women typically do not demonstrate an exercise-induced increase in testosteroneas a result of exercise.

Growth Hormone

Secreted from the pituitary gland and made from over 190 amino acids, growth hormone may:• Increase protein synthesis• Increase fat breakdown• Increase collagen synthesis• Decrease glucose utilization

Growth hormone secretion is at its peak during adolescence. After we get into our twenties, ourbodies start to produce less of it. With good nutrition, sleep and training we can delay this decrease ingrowth hormone.

Many of these hormones actions may be helped by Insulin-like Growth Factor. Growth hormonestimulates both the release of IGF’s and the availability of amino acids for protein synthesis. Withoutgrowth hormone, IGF cannot be released by the liver.

The time of day affects the blood secretion levels with the highest levels observed at night. Trainingcan affect GH. High lactate concentration from hypoxia can cause greater GH concentrations. Resistanceprotocols with light loads with high repetitions don’t seem to affect serum concentrations. It seems 5–10repetitions combined with short rest periods (under 1-minute) works best with the most dramaticincreases occurring in response to the decrease in rest periods. Growth hormone is often said to have anti-insulin activity, because it suppresses the abilities of insulin to stimulate uptake of glucose in peripheraltissues and enhance glucose synthesis in the liver.

Insulinlike Growth Factors

Many of the effects of growth hormone are mediated by Insulinlike growth factors, (IGF’s). IGF’stravel in the blood attached to binding proteins, then are released as free hormones to interact withreceptors. Increases in blood levels of IGF are unknown but probably related to the disruption of variouscells, including fat and muscle cells since both these cells manufacture and store IGF. Fat cells haverelatively high levels of IGF in comparison to skeletal muscle, which has very little of its own. With highintensity training it has been shown the IGF rose at some point over the two hours following exercise.

Insulin

Released by the pancreas, insulin increases cellular uptake of glucose synthesizing muscle glycogenwhich in turn decreases in blood glucose. During prolonged workouts, blood glucose reduction along withdecreased insulin production increases the mobilization of fat.

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Cortisol

Secreted by the adrenal gland, cortisol is catabolic and causes a breakdown of protein in the muscles.Cortisol is an antagonist which inhibits glucose uptake and utilization. Too much can cause Ketosis,especially if a client is on a carbohydrate restricting diet. Cortisol has a greater catabolic effect in fast-twitch muscles than in slow-twitch muscles. Interestingly enough the acute exercise protocols thatproduce the highest catabolic responses in the body also produce the greatest growth hormone response.It seems muscles must be broken down or disrupted to a certain degree in order to rebuild themselves andenlarge. Elevations in cortisol would help in this process.

Catecholamines

Released by the adrenal glands the “fight-or-flight” hormones, epinephrine, norepinephrine anddopamine are released in response to stress. It would then make sense that studies have shownepinephrine to increase with heavy resistance training. Heavy resistance training is very stressful on thebody. Since epinephrine is involved in metabolism, force production and the rate of response of otherhormones such as testosterone and IGF’s, the stimulation of catecholamines is probably one of the firstneuroendocrine mechanisms to occur in response to resistance exercise.

CARDIOVASCULAR SYSTEM

The cardiovascular system is a transport system that serves to integrate the body as a whole. Its roleis to provide a continuous influx of oxygen and nutrients and as an outlet for carbon dioxide and waste.The components of the cardiovascular system are a pump, a high-pressure distribution system, gasexchange units, and a low-pressure collection and return system. The blood acts like a taxicab for gases(like oxygen) and nutrients (like glucose) to be delivered to all the cells in the body. Blood also retrievesgases (like carbon dioxide) from all cells and carries them to be expelled or metabolized. Blood pressureis the pressure in the arteries during the two phases of the cardiac cycle: systole and diastole. Systole, orsystolic, is the pressure of the arteries during ventricular contraction. Diastole, or diastolic, is thepressure of the arteries during ventricular filling. Normal blood pressure is 120/80 where 120 is thesystolic pressure and 80 is the diastolic pressure. 140/90 is considered mild hypertension or high bloodpressure. When performing dynamic exercise, heart rate and systolic pressure should increase butdiastolic pressure remains the same. The Valsalva maneuver is the attempt to exhale with the glottistightly shut. This maneuver has been shown to increase blood pressure and can be potentially harmful tosome individuals.

Cardiac output is the result of stroke volume times heartbeats per minute.

Cardiac output is the primary indicator of the functional capacity of the circulation to meet thedemands of the physical activity. Output from the heart, as with any pump, is determined by its rate ofpumping (heart rate) and by the quantity of blood ejected with each stroke (stroke volume). Outstandingendurance athletes frequently have a low resting heart rate and a high VO2 max.

Thus, cardiac output is computed as:Cardiac output = Heart rate x Stroke volume

The total capacity to consume oxygen in the cells is called the Maximum Oxygen Capacity, or VO2.VO2 max (also maximal oxygen consumption, maximal oxygen uptake or aerobic capacity) is themaximum capacity of an individual’s body to transport and utilize oxygen during incremental exercise,

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which reflects the physical fitness of the individual. The name is derived from V = volume per time, O2

= oxygen, max = maximum.

VO2 max is expressed either as an absolute rate in litres of oxygen per minute (l/min) or as a relativerate in millilitres of oxygen per kilogram of bodyweight per minute (ml/kg/min), the latter expression isoften used to compare the performance of endurance sports athletes

MAX. Maximum Heart Rate (MAX HR) is the theoretical maximum beats per minute a heart canpump. This maximum declines with age and is given in the formula:

MAX HR = 220 – AGE = MHR (age predicted max heart rate)

Target training range is a specific percentage of the max heart rate in which the heart is targetedto stay within. Here are three equations to help you determine a target heart rate for your client:

220 – AGE x % = THR (Attainable heart rate), THR = Target Heart Rate

220 – AGE – RHR (Resting heart rate) x% + RHR = THR (Karvonen Theorem based on heart ratereserve)

220 – Age x% x 1.15 = THR (Target Heart Rate)

The standard of deviation for all of these equations is plus or minus +/-10 bpm. Remember theseare people. Consider their medical history and their families’ medical history.

In some instances it might be better to use the Borg Scale of Perceived Exertion, especially on aclient’s first session. In using this scale, you would be able to establish a means or communication bywhich clients can express their feelings in relation to levels of exercise intensity.

The original rating scale was from 6–20 and mirrored your heart rate. The number 6 was comparableto 60 beats per minute which we know is very, very light exercise and 19 was comparable to 190 BPMwhich is very, very hard. They revised it to a scale of ten points from 1–10.

6 0 = nothing at all7 very very light 1 = very light8 2 = light (weak)9 very light 3 = moderate10 4 = somewhat hard11 fairly light 5 = heavy (strong)12 613 somewhat hard 7 = very heavy14 815 hard 916 10 = very, very heavy (maximal)17 very hard1819 very, very hard20

The following instructions are recommended when administering the RPE scale. (Health & Fitness

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Instructors Handbook, third edition) “During this exercise we want you to pay close attention to how hardyou feel the exercise work rate is. This feeling should reflect your total amount of exertion and fatigue,combining all sensations of physical stress, effort and fatigue. Don’t concern yourself with any one factorsuch as leg pain, shortness of breath or exercise intensity.”

The anaerobic threshold is the intensity level where the cardiovascular system is unable to supplyenough oxygen to exercising muscles. This threshold could occur anywhere between 50–85 percent ofthe max heart rate.

THE HEART

The heart provides the pump for continuous blood flow throughout the body. The heart muscle, calledmyocardium, is a striated muscle similar to skeletal muscle and is completely comprised of Type I fibers.There are four chambers located in the heart. The top chambers, called atriums, serve as temporarystorage for blood immediately before flushing into the main pumps in the bottom chambers, calledventricles. Deoxygenated blood returning from the lower body travels through the inferior vena cava veinand deoxygenated blood returning from the upper body travels through the superior vena cava vein. Thesetwo veins meet at the right atrium of the heart to fill the right atrium. When the right ventricle contracts,the vacuum effect created in the ventricle draws in the blood from the atrium for the next ventriclecontraction. Blood pumped from the right ventricle travels through the pulmonary arteries to the lungswhere oxygen is picked up by the blood. Bloodis then transported back to the heart via thepulmonary veins and into the left atrium. Whenthe left ventricle contracts, the left atrial bloodis flushed down into the ventricle and awaitsthe next contraction. Blood pumped from theleft ventricle travels through the aorta (themain artery that supplies blood to themyocardium) to deliver fresh oxygenatedblood to all the cells in the body. Abrubtlystopping vigorous activity can be dangerousbecause the blood which is pooled in thee x t remities may not be delivered quicklyenough to the heart and brain. This is calledvenous pooling.

The systemic effects of cardiovascularexercise include: increased stroke volume,increased oxygen utilization, decreased bloodpressure, and decreased resting heart rate. Theperipheral effects of cardiovascular exerciseinclude: increased number and size ofmitochondria, increased glycogen, increasedrelease of fatty acids, and increased capacity tooxidize fat.

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HEART RATE ZONES

Target Heart Rate or Training Heart Rate (THR) training range is a specific percentage of themaximum heart rate in which the heart is targeted to stay within. Depending on the stage of training orthe fitness goal will dictate which “zone” to exercise in.

Zone 1 will normally occur at 40%–65% of MHR (based on VO2 max) which we will call the“Recovery zone”. Zone 2 or “aerobic endurance” zone will normally occur between 65%–85%. Above85% would be Zone 3 your “Peak Zone.” The Anaerobic threshold (AT) is the intensity level where thecardiovascular system is unable to supply enough oxygen to exercising muscles. This threshold couldoccur anywhere between 60–85 percent of the max heart rate with the norm occurring at about 5– 60%in un-trained individuals. Improvements following endurance training can raise values to 75% and inelite world-class athletes, values of 80–90% have been reported.

If fat-loss is the goal, then the THR will be 40 - 65% of the person’s VO2 max. If using the Karvonenor the 220 - age - RHR x % + RHR = THR (training heart rate). For a 30 year old with a resting heart rateof 72 bpm in Zone 1, could go like this: 220 - 30 - 72 x 60% + 72 = 142.8 or 143 BPM. Here’s theproblem, this equation works for about 80% of the population. If you have an abnormally high or lowresting heart rate or happen to be genetically gifted with a high VO2 max, this equation will underestimateor overestimate your training zones. Using the Attainable Heart Rate equation for the same person wouldbe: 220 - 30 x 80% = 152 BPM. That’s a difference of almost 10 BPM! Remember, people are different.Use these equations as a guideline. Observe your client closely and communicate with them. The mostaccurate way to determine heart rate zones is to have a VO2 max test done using respiratory exchange.

BENEFITS OF CARDIOVASCULAR TRAINING

The systemic effects of cardiovascular exercise include:

• Increased stroke volume

• Increased oxygen utilization

• Decreased blood pressure

• Decreased heart rate

The peripheral effects of cardiovascular exercise include:

• Increased number of mitochondria

• Increased glycogen

• Increased release of fatty acids

• Increased capacity to oxidize fat

After cardiovascular exercise or weight training, the body continues to need oxygen at a higher ratethan before the exercise began. This sustained oxygen consumption is known as Excess PostexerciseOxygen Consumption (EPOC) or also referred to as oxygen debt. During EPOC the body is restoringitself to its pre-exercise state, and thus is consuming oxygen at an elevated rate. This means that energyis also being expended at an elevated rate. The evidence suggests that a high-intensity, intermittent-typeof training (interval training) has a more pronounced effect on EPOC (Haltom et al. 1999). Also, it

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appears that resistance training produces greater EPOC responses than aerobic exercise (Burleson et al.1998). It has been suggested that high-intensity resistance exercise has a larger energy requirement thanaerobic exercise therefore has a higher EPOC. However, the studies didn’t specify the intensity of aerobicexercise. It is my anecdotal opinion that the longer and closer one can exercise at their VO2 max, thehigher the EPOC. Keep this in mind when the goal is weight control.

TRAINING PRINCIPLES

There are five major training principles one must incorporate into a fitness program:Overload principle: The attempt to challenge the musculoskeletal system with unaccustomed

stimulation such as, but not limited to, increased weight, speed, or volume of training (numberof sets or reps).

Specificity: The focused effort of exercise in a certain way such as anaerobic/aerobic,strength/endurance. S.A.I.D. Principle: Specific Adaptation to Imposed Demands.

Individual Difference: The taking into account the genetic makeup, exercise history, fiber typeratio, motivation level, and anatomical physics of the body.

Reversibility: A major decrease in strength and aerobic capacity are apparent after two weekswithout exercise, and a major decrease in anaerobic capacity after three weeks withoutexercise.

Periodization: The gradual cycling of workout parameters such as specificity, intensity, orvolume to achieve a specific goal.

PHYSIOLOGICAL CHANGES

The physiological changes that can occur from exercise training involve all the major systems of thebody:

• Increase in lean body mass and a decrease in body fat.• Increase in joint integrity due to strengthened ligaments and connective tissue.• Decrease in injuries from a higher capacity of muscles to perform work.• Increased skill in performing the exercise.• Increase in bone density from the compressive forces on the skeletal system.• An enhanced immune system, from the lymphatic system being optimized through muscular

contraction.• Better sleep habits, due to regulation of hormones and an actual need to rest and recuperate.

Overtraining

For some people and most athletes, the hardest thing to do is not exercise. However, if the person isnot rested enough or has not recuperated from the day before, training or exercising that day could domore harm than good. It’s imperative that you know the resting heart rate in the morning, or at least knowthe resting heart rate before a given activity for the person that is exercising. For example, if the heart ratefor a person sitting on their bicycle is 72 bpm and you check their heart rate and it’s at 98 bpm, it mightbe a better idea to rest that day or lower the intensity or volume of the planned workout for that day. Thisperson might be overtrained.

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Overtraining Signs and Symptoms:

• Elevated resting heart rate• Elevated resting body temperature• Difficulty sleeping, restlessness or feeling “overheated”• Fatigue or “feeling stale”• Irritability• Decreased interest in training• Immune system breakdown• A “runny nose” or a tendency to get sick• A failure to progress• Excessive weight-loss• Frequent muscle cramps or muscle strains• Excessive soreness• Ammenoria (no menstruation)

If you or your clients experience any of these symptoms, reduce the exercise intensity, the volume,duration or change the type of exercise. If the symptoms persist, see a medical doctor.

FIVE MAJOR FACTORS THAT AFFECT TRAINING

Level of fitness is based on one’s history of exercise. Obviously, the more total hours of training,the greater the results.

Intensity is a much-overlooked component of training. To break old records and to realize one’spotential, the exertion level or intensity, must be raised another notch.

Duration can affect training in two ways. For anaerobic training, exercise should not last morethan 60 minutes. Optimal levels of hormones fall drastically if intense exercise lasts 75minutes. For aerobic training, exercise duration must last at least twenty minutes continuouslyfor aerobic effects to occur.

Frequency of exercise should be fairly high for training, ideally 4–5 times a week for consistencyof adaptation.

Genetics play a big role in one’s potential and should be considered when planning long-termgoals.

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REFERENCES

1. McArdle WD, Katch VL, Katch F1: Exercise Physiology: Energy, Nutrition, and Human Performance. Philadelphia: Lea & Febiger, 1986.

2. Brooks GA, Fahey TD: Exercise Physiology: Human Bioenergetics and Its Applications. New York: John Wiley & Sons, 1984.

3. Huxley AF: Muscular Contraction. J Physiol (London) 243:1, 1974.

4. Salmons S, Henriksson J: The Adaptive Response of Skeletal Muscle to Increased Use. Muscle Nerve, 4:94, 1981.

5. Costill DL, et al.: Adaptations of Skeletal Muscle Following Strength Training. J Applied Physiology, 46:96, 1979.

6. Armstrong R: Biochemistry: Energy Liberation and Use in Sports Medicine and Physiology.Edited by RS Strauss. Philadelphia: W.B. Saunders, 1979.

7. Reid JG, Thomson JM: Exercise Prescription for Fitness. Englewood Cliffs, NJ: Prentice-Hall, 1985.

8. Guyton JG: Physiology of the Human Body. 5th Ed. Baltimore: Williams & Wilkins, 1976.

9. Anthony CP, Thibodeau GA: Textbook of Anatomy and Physiology. 11Ed. St Louis: C.V. Mosby,1983.

10. Gollnick, P.D.: and Hermansen, L.: Biochemical Adaptations To Exercise. Anaerobic Metabolism.In Exercise and Sports Sciences.

11. Liebenson, Craig: Rehabilitation of the Spine, Williams & Wilkins, 1996.

12. Smith, Jessica: IDEA Source, May, 2002, Revisiting Energy Systems -Tables 2-1 and 2-2.

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