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Theme Issue: Exercise and Sports

Principles of Exercise Physiology: Responses to AcExercise and Long-term Adaptations to Training

Anita M. Rivera-Brown, PhD, Walter R. Frontera, MD, PhD

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Abstract: Physical activity and fitness are associated with a lower prevalence odiseases, such as heart disease, cancer, high blood pressure, and diabetes. Thdiscusses the body’s response to an acute bout of exercise and long-term physadaptations to exercise training with an emphasis on endurance exercise. An ovprovided of skeletal muscle actions, muscle fiber types, and the major metabolic pinvolved in energy production. The importance of adequate fluid intake duringsessions to prevent impairments induced by dehydration on endurance exercise,power, and strength is discussed. Physiological adaptations that result from regulartraining such as increases in cardiorespiratory capacity and strength are mentioreview emphasizes the cardiovascular and metabolic adaptations that lead to improin maximal oxygen capacity.

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INTRODUCTION

For decades, exercise has been used by physiologists as a research tool to undersworkings of several body systems, particularly the skeletal muscle, metabolism, tand the peripheral circulation. More recently, physiologists have focused on underexercise itself, because regular physical activity has been shown to be important foprevention and health promotion. The purpose of this focused review is to discurrent understanding of the human body’s response to an acute bout of exerciseuse endurance exercise as an example of this response. For more detailed discuother types of exercise, the reader is referred to several alternative sources. In the secof the review, we also comment on the long-term adaptations induced by enexercise in some physiological systems.

TYPES OF SKELETAL MUSCLE ACTIONS

Movement, exercise, and sports require the generation of force by skeletal muscForce can be generated while skeletal muscles remain static, become shorter, or inlength [1]. These actions are the result of biochemical and structural changes that twithin the skeletal muscle fibers after neural activation and that need energy in thadenosine triphosphate (ATP). During most types of exercise, muscles alternatestatic and dynamic muscle actions.

Static (Isometric) Muscle Actions

Static muscle actions occur when the muscles generate force without changing lenthere is no associated joint movement. In static actions, the myosin and actin myoform cross-bridges and generate force, but the external resistance (weight of theobject) is greater than the force produced by the muscle. Although there iexpenditure, no work (work � force � distance) is done because there is no displAn example of this type of muscle action is the performance of a cross on the rings a

by a gymnast (Figure 1).

PM&R © 2012 by the American Academy of P1934-1482/12/$36.00

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A.M.R.-B. Department of PhysicRehabilitation, and Sports Medicinof Puerto Rico School of MedicinPuerto Rico; Center for SportsExercise Sciences, PO Box 20Puerto Rico 00751. Address corto: A.M.R.-B.; e-mail: aniriver.brcomDisclosure: nothing to disclose

W.R.F. Department of Physical MRehabilitation, Vanderbilt UniverCenter, Nashville, Tennessee; DPhysiology, University of Puerto

of Medicine, San Juan, Puerto RicoDisclosure: nothing to disclose

hysical Medicine and RehabilitationVol. 4, 797-804, November 2012

ttp://dx.doi.org/10.1016/j.pmrj.2012.10.007797

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798 Rivera-Brown and Frontera PRINCIPLES OF EXERCISE PHYSIOLOGY

Dynamic (Isotonic) Muscle Actions

Dynamic muscle actions can be divided into conceccentric muscle actions.

Concentric Actions. During concentric actimuscles produce enough force to overcome theresistance, myosin and actin myofilaments formbridges, the filaments slide pass by each othershortening occurs, and joints move. Given thatforce production and displacement, energy expresults in work (sometimes referred to as positivThis type of muscle action is used when movingduring exercise (ie, running) or sports activities (Fand/or when moving external objects.

Eccentric Actions. During eccentric actions, thlengthens while it generates force. The lengtheninbecause the external resistance moves in the dopposite to the shortening. Eccentric actions can

Figure 1. A gymnast performing the Iron Cross,executed by extending both arms straight out fromof the body and holding the isometric muscle actsuspended in the air. Printed with permission.

untary, such as when lowering a barbell after a biceps c

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exercise, or involuntary, such as when the persodropping a heavy object. Because the displacemthe direction opposite to the standard concentrieccentric muscle actions are sometimes known asing negative work. These muscle actions providportant training stimulus because of the high forcated by the contractile elements. Eccentric actiobeen associated with muscle damage and sorenesis recommended that, at least initially, the eccentponent of exercise training be limited. The use of eactions is of particular clinical value during thetation of tendon injuries [2].

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799PM&R Vol. 4, Iss. 11, 2012

Dynamic (Isokinetic) Muscle Actions

Isokinetic muscle actions are characterized by conlocity, a condition that exists in the laboratory or cnot in nature [3]. Isokinetic actions can be conceccentric, and require special (and usually expensiputerized equipment to maximize resistance at eachthe range of motion. These devices can be used for trfor testing purposes. Athletes may use isokinetic dperform exercises that simulate the actual speedssport-specific activities.

MUSCLE-FIBER TYPES

Human skeletal muscle is a heterogeneous tissue inthat muscle fibers vary in terms of their mechanicallogical, and biochemical properties (Table 1).methods have been used to classify skeletal muscincluding histochemical techniques, such as ATPoxidative enzyme stains, measurements of co(twitch) or fiber-shortening velocity, and the identifithe myosin heavy chain isoform by using protein eleresis. In general, human skeletal muscles may contaiof fibers in varying proportions: fiber types I, IIa, anFibers that express type I myosin heavy chain isoforslow, oxidative, fatigue-resistant fibers. Type IIhowever, are very fast contracting, glycolytic, andfibers. Type IIa fibers have intermediate propertiefast contracting but with an oxidative metabolic pis important to note that human muscle fibers canmore than one type of myosin heavy chain isoformtaneously [4]. These fibers are known as hybrid fivarious combinations (I/IIa, IIa/IIx, I/IIa/IIx) hareported. These hybrid fibers may be more prevmuscles recovering from injury, aging, and unstrength training.

ACUTE METABOLIC RESPONSESDURING EXERCISE

Energy drawn from high-energy phosphate bonds ifor muscle activity. The cell stores a small amounnear the contractile proteins [3]. The use of this Adependent on a supply of oxygen, and, therefore, th

Table 1. Characteristics of muscle-fiber type

Muscle-FiberType

ShorteningVelocity

MetabolicProfile F

I Slow Oxidative RIIa Fast Intermediate InIIx Faster Glycolytic F

*Fiber-type distribution is highly variable in humans; this classificsport and the predominant fiber-type distribution.

is available as soon as the muscle requires it. For exercise

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continue beyond a few seconds, cells must synthethrough 1 of 2 metabolic pathways: anaerobic (glycoaerobic (oxidative). All energy systems contribute toenergy demands of different sporting events butpredominate according to the sports-specific chara(predominantly aerobic or anaerobic).

Activities that depend primarily on the ATP-phoatine (PC) system and anaerobic glycolysis are clasanaerobic activities. Examples of exercises in thisinclude 100-800-m track races, golf or tennis swinging events in track and field, and other events thamuscle activity for 2-3 minutes [5]. Activities of longtion (�2-3 minutes) that depend primarily on ometabolism, such as long-distance swimming andare classified as aerobic activities. Many sports actiquire a blend of both anaerobic and aerobic me(Figure 3). In “stop and go” sports such as baskettennis, approximately 60%-70% of the energy comATP-creatine phosphate (CP) stores and anaerobic gand the remaining 30% from oxidative processes [6

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Isoform Type Sports Predominan

t I Long duration (marathondiate IIa Team sportsle IIx Sprints, weight lifting

only intended to illustrate the relationship between the metabolic demands of

Figure 3. In a 2-minute round of boxing, anaerobic atriphosphate resynthesis contributes the majority ofenergy required for muscle actions during the first 30and aerobic metabolic energy provision predominalast part of the round; training programs should inclucises that train both metabolic pathways. Reprinted

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800 Rivera-Brown and Frontera PRINCIPLES OF EXERCISE PHYSIOLOGY

ANAEROBIC METABOLISM

Stored ATP and CP

Energy at the onset of exercise and for muscle avery-high intensity (85%-100% of maximal capactherefore, of short duration (up to 10 seconds) isfrom a small amount of ATP and CP that is stored icells [5-7]. The total energy available in stored Aenough for short-duration exercise, such as a weighhigh jump (Figure 4), or a 10-second sprint.

Anaerobic Glycolysis

During high-intensity exercise, the cardiovascularunable to supply the cells with oxygen quickly enactivity is to continue, once the ATP-CP stores are exthe muscles resort to the rapid breakdown of storegen-glucose for ATP regeneration via the glycolytic[6]. Anaerobic glycolysis can provide energy for eveas the 400-800-m sprints and during the beginninintensity exercise when muscle energy needs are higoxygen transport system is not yet fully activated.nately, this may result in the production and accumulactic acid, which leads to fatigue because muscletion impairs enzyme function, decreases the calciumcapacity of muscle fibers, and impairs the muscability to generate force. The fuel used in anaerobic gis carbohydrates. Each mmol of glucose or glycogen3 mmol of ATP. Patients with certain types of mmyopathies may have limited capacity to generateperform exercise due to enzymatic abnormalities in

Figure 4. The energy needed to perform a highderived from the adenosine triphosphate and creatphate that is stored in muscle cells. Printed with perm

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AEROBIC METABOLISM

If exercise intensity is low and there is a steady soxygen to the cells, then energy is produced via ophosphorylation [7]. The oxidative system has a higyield and is the most important pathway for energytion during prolonged exercise. This aerobic procplace in the mitochondria of active muscles andKrebs cycle and the respiratory chain. The energyaerobic metabolism is much higher than thatthrough anaerobic glycolysis: 36-39 mol of ATPgenerated per mmol of glycogen. Fats also enter thcycle and the respiratory chain after being broken dmetabolic process known as �-oxidation. Amino acidconverted to glucose or to various intermediates of ometabolism, but in general, they contribute little tproduction.

Oxygen Transport Chain

Oxidative phosphorylation is dependent on a cosupply of oxygen. Because the amount of oxygen scells in hemoglobin and myoglobin is small andduration, oxygen must be replenished from the envirA series of mechanisms ensure an adequate supply oto the site of oxidation in the mitochondria of activuptake of environmental oxygen through alveolartion, diffusion of oxygen into the blood, flow of blotissues, and, finally, diffusion of oxygen into musand mitochondria [8]. Different pathologic proceinterfere with one or more of these steps andpatient’s exercise capacity. However, a strong relahas been shown between exercise performance inance sports and the capacity for oxygen transpoworking muscles [9].

Oxygen Uptake and Exercise Intensi

When a person exercises at progressively higher-poputs, there is a linear increase in oxygen uptake to mdemand of the active skeletal muscles until theoxygen consumption (VO2 max) is reached. The VOan indicator of the system’s ability to deliver oxygenmuscle as well as a biomarker of health. Individualable to continue exercising for a short period of timeVO2 max is reached because energy can be providedanaerobic processes, for example, glycolysis. The Vcan be twice as high in trained athletes comparsedentary individuals because of their enhanced strume, improved myocardial function, and higher capoxidative metabolism in active muscles. Patients wdisease, heart disease, and peripheral vascular disealow VO2 max. Healthy young individuals have anVO2 max value of 38 mL/kg per minute (women)

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801PM&R Vol. 4, Iss. 11, 2012

creases in aerobic fitness, as measured by VO2 mbeen related to a reduction in death from all causes.max can increase by approximately 15% with trathough there is significant intersubject variability.

ACUTE CARDIOVASCULAR RESPONSEDURING EXERCISE

The determinants of oxygen consumption are summthe Fick equation as follows:

VO2 � CO � (CaO2 � CVO2),

where VO2 is oxygen consumption, CO is cardiacand CaO2 – CVO2 is the O2 difference between artvenous blood, or the a-vO2 difference [10,11]. Thare 2 major factors that could limit VO2 max: cardiaand the capacity of active muscle to extract oxygarterial blood.

Cardiac Output

Cardiac output is the product of stroke volume arate. In general, cardiac output increases linearly wcise intensity, from a resting value of approximatelyto 20-40 L/min, depending on the level of condDuring exercise, there is a redistribution of blood floapproximately 95% of the CO is diverted to the hactive skeletal muscles. In healthy individuals, strokincreases with increasing power output up to appro40%-60% of the VO2 max and then levels off [12]. Tthe increase in CO with increasing exercise intensimarily mediated by increasing heart rate. Duringexercise in the upright position, stroke volume canfrom 50 mL at rest to 120 mL. In the supine positiodoes not pool in the lower extremities and venousenhanced. Thus, resting stroke volume values arethe supine position, and the increase in stroke volumexercise, such as in swimming, is only approximat40% of the resting value.

a-VO2 Difference (CaO2 – CVO2)

The a-vO2 difference is an indicator of the effectivactive muscles in extracting oxygen from arterial brest, approximately 20%-30% of the blood’s originacontent (20 mL of oxygen per 100 mL of arterialextracted at the tissue level. In the absence of lungCaO2 is constant (at rest and during exercise) andreduced during exercise, thus the a-vO2 differenceprogressively with exercise intensity.

Blood Pressure

In healthy individuals, both systolic and mean blo

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pressure remains relatively unchanged [10,11,13exercise is performed with the arms only, then the inblood pressure is approximately 10% greater thaexercise is performed with the legs because the smacle mass and vasculature of the arms present greatance to blood flow. Thus, arm exercise should be dcaution by individuals with cardiovascular diseaseexercise that involves static muscle actions, there isate increase in cardiac output and a localized vasotion that restricts blood flow. This combination cauin systolic, diastolic, and mean blood pressures thatthan during dynamic exercise at similar exerciseand intensity [10]. During maximal static muscle athe arms, systolic and diastolic blood pressures ca220 and 150 mm Hg, respectively.

LIMITATIONS TO OXYGEN CONSUMPTDURING EXERCISE

Chronic inactivity as well as several medical co[11,12,14] can impair one or more of the mechanvolved in either oxygen transport (stroke volumheart rate) or oxygen utilization (CaO2 or CVO2

results in a decrease in VO2 max and impairedperformance. For example, patients with aortic stena low stroke volume during exercise due to the iresistance imposed by the stiff aortic valve, which lreduction in maximal cardiac output, muscle blood floxygen delivery, and to low exercise tolerance. Patieuse �-blockers have a slower heart rate at restincrease associated with exercise is less. Conditionsresult in a reduction in arterial oxygen content, for easthma, may impair oxygen delivery and exercisemance. Finally, diseases such as muscular dystropimpair the capacity of muscles to extract oxygen.

FACTORS THAT AFFECT AEROBIC EXEPERFORMANCE

The capacity for prolonged exercise and sports perfis also dependent on other factors, such as muscle bcapacity, gender, age, and genetics [15-21].

Acid-Base State of Muscle

As mentioned above, lactic acid, a metabolic bypranaerobic glycolysis, increases the intracellular amuscles and impairs muscle actions. The lactate threthe exercise intensity at which lactate begins to accua good indicator of the individual’s performance inance events.

Gender

Women have smaller hearts, lower blood volumes, a

od hemoglobin concentrations, which result in a lower stroke

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802 Rivera-Brown and Frontera PRINCIPLES OF EXERCISE PHYSIOLOGY

volume and blood oxygen carrying capacity. WomeVO2 max that is approximately 75% that of men; thirelated difference is lower when adjusted for diffesize and body weight.

Age

With increasing age, there is a decline in aerobicpartially due to a reduction in habitual physicalAerobic capacity decreases by approximately 10% pein men and women [19-21]. In athletes who maintalevel of endurance training, the decline in VO2 mproximately half that of sedentary men (approximper decade). The primary factor that causes the redVO2 max with age is a reduction in cardiac outpuincreased peripheral resistance and lower stroke vo

Genetics

Studies on identical and fraternal twins have suggegenetics account for 20%-30% of VO2 max values [1appears that elite endurance athletes are born wittional genetic potential for the development of a vlevel of cardiorespiratory fitness.

HYDRATION AND MUSCLE FUNCTIONDURING EXERCISE

During exercise, a substantial volume of body watelost via sweating to enable evaporative cooling, esphot environments [16,23]. Sweating rates can be ofhour and even higher in well-trained and heat-accathletes [23]. Individuals who exercise for prolongedmust drink fluid to restore the body’s water loss anddehydration [24]. Furthermore, many athletes carrdeficit from their previous workout into the nextwhereas others purposely dehydrate to “make weighsports competition [25].

The negative consequences of dehydration inincrease in cardiovascular strain, hyperthermia, imof exercise performance, and an increased risk forness. Dehydration of as little as 2% of initial body w

Table 2. Exercise prescription model

Fitness Component Type of Exercise

Muscle strength andendurance

8-10 exercises: major musclfree weights, pulleys, elastisokinetic dynamometer

Cardiorespiratoryendurance

Walking briskly, jogging, swcycling, rowing, dancing,endurance sports, prolongduration sports

RM � repetition maximum; reps � repetitions; HRR � heart rat

impair endurance [23]. In addition, the available eviden

e aer-in

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suggests that a dehydration of 3%-4% of initial bodappears to diminish muscle strength by approximamuscle power by approximately 3%, and high-intedurance (activities that last �30 seconds but �2 minapproximately 10% [26]. Exercise-associated muscl[27] appear to be more prevalent during prolongedin hot and humid conditions, especially in fatiguedrated individuals and in those with high sweatlosses (“salty sweaters”). As a result of extracellular wwith dehydration, a mechanical deformation of neings may occur, which causes selected motor nerve tto become hyperexcitable and spontaneously disch

EXERCISE PRESCRIPTION FOR THEDEVELOPMENT OF PHYSIOLOGICALCAPACITIES

According to the 2008 Physical Activity Guidelines focans [28], all adults need at least 2 hours and 30 minuminutes) of moderate-intensity aerobic activity everyaddition to muscle-strengthening activities that exmajor muscle groups on 2 or more days a week.physical activity and exercise can result in long-tetional and health benefits, such as a reduction in thdeveloping chronic diseases such as heart disease, soof cancer, and type 2 diabetes [28]. An exercise preincludes the type of exercises, frequency of the sessioper week), intensity, and duration of the sessions (T

LONG-TERM PHYSIOLOGICALADAPTATIONS TO ENDURANCE EXERCTRAINING

Exercise training is associated with significant adaptmany physiological systems that are specific to thetraining. This section will briefly summarize the matations to one type of exercise training that emphadurance. Other sources present a more detailed discthese adaptations [6,11,16].

Endurance training elicits many adaptations inmuscles and in the metabolic and cardiorespiratory

Frequency, d/wk Intensity D

ps;ds

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803PM&R Vol. 4, Iss. 11, 2012

deliver and utilize oxygen for energy production, thefor prolonged exercise, sports performance, and thmance of activities of daily living without undue fhas been estimated that gains in maximal aerobicafter endurance training are strongly influenced by[29].

Metabolic Adaptations in Skeletal M

Endurance training causes an increase in the nucapillaries per muscle fiber and in the number anmitochondria in skeletal muscles [30-32]. The newies that form in trained muscles result in an increaseflow to active muscles and provide a greater surfacethe exchange of gases during exercise. The increasechondrial content and concentration of enzymes incarbohydrate and lipid metabolism enhances theoxidative capacity and ability to extract and utilizfrom arterial blood. As a result, glycogen stores arand lactate production at a given exercise intensity isincrease in mitochondria in the subsarcolemmal regmuscle fibers shortens the diffusion distance for ox

Cardiovascular Adaptations

Endurance training increases plasma and total bloodOf importance is the fact that this effect is noted wfirst 7-10 days of training. The increase in plasmaalso results in relative hemodilution and a lower hemconcentration (runner’s pseudoanemia). The low bcosity enhances the movement of blood through theies and may improve oxygen delivery to the activeAt the level of the heart, the increase in plasma voluman increase in end-diastolic volume and in the elasticthe left ventricle [33]. Endurance training also leaincrease in left ventricular muscle mass and dilata

Table 3. Summary of cardiovascular and metabolictions with endurance training

PhysiologicalParameter Rest

SubmaximalExercise

Stroke volume 1 1Heart rate 2 2Cardiac output — —a-vO2 difference — 1VO2 — —Systolic blood pressure 2 2Diastolic blood pressure — 2Blood volume 1 1Capillary density 1 1Mitochondrial density 1 1

1 � increase;2 � decrease; — � no change; a-vO2 � (CaOVO2 � oxygen consumption.

results in a more forceful contraction. Both of these adap

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tions enhance the ejection fraction and stroke volumand during submaximal and maximal exercise.

Resting heart rate decreases after a few weeks of entraining due to an increase in parasympathetic activreduction in sympathetic activity [34]. A submaximrate at the same relative exercise intensity also decregenetics play a determinant role in this response to[35]. Maximal heart rate decreases or remains unchlower maximal heart rate allows for an increase intricular filling time so that maximal stroke volumediac output are optimized. Resting and submaximaoutput do not change significantly after endurancebut, because of the increase in maximal strokemaximal cardiac output increases significantly afterFinally, endurance training causes a reduction in ressubmaximal systolic and diastolic blood pressurehealthy individuals and in patients who are hyp[36]. The cardiovascular mechanism that leads to anin VO2 max is dependent on age, with adaptationspeople more dependent on changes in the a-vO2 dand less on cardiac output [37].

SUMMARY

Regular exercise is important to improve physiologition, physical fitness, and health. Physical activity anare associated with a lower prevalence of manydiseases such as heart disease, cancer, high blood pand diabetes. Exercise activities can be categorizedof the major metabolic pathway involved in energy ction: predominantly aerobic or predominantly anRepeated bouts of exercise result in significant adaptmany physiological systems of the body. Furtheraerobic exercise leads to an improvement in VO2

reflects several cardiovascular and metabolic adaAlthough the VO2 max has a significant genetic comand it is affected by the aging process, it can improvicantly with training at any age and in both genders.training should include exercises to increase strenendurance.

REFERENCES1. Behm DG. Neuromuscular implications and applications o

training. J Strength Cond Res 1995;9:264-274.2. Witvrouw E, Mahieu N, Roosen P, McNair P. The role of st

tendon injuries. Br J Sports Med 2007;41:224-226.3. MacDougall JD, Wenger HA, Green HJ. Physiological Tes

High-Performance Athlete. 2nd ed. Champaign, IL: Huma1991.

4. Canepari M, Pellegrino MA, D’Antona G, Bottinelli R. Sinfiber properties in aging and disuse. Scand J Med Sci Sport10-19.

5. Bogdanis GC, Nevill ME, Boobis LH, Lakomy HK. Contphosphocreatine and aerobic metabolism to energy sup

ta-

alise

—

2);

ta- repeated sprint exercise. J Appl Physiol 1996;80:876-884.

d Exerc

tion duin Exermance

ard Uni

nts of thly trai

Y: Oxf

or Exertt Willi

olume dports Ex

ic, andse to E

5-173.d coronCircula

f VO2mGE Fam

Physiolo2005.ysiol 19

Univer

, Blairports Ex

, BlairSci Sp

ging ampl Phy

s of aero

J, Stachen-e of Sports7-390.Effects onb DR, eds.

omeostasis.adolescentrts Physiol

d muscularand high-

ps. Muscle

cal Activityhealth.gov/2012.

r classifica-endurance-1496.g-induced

ences with. J Physiol

content of(Suppl 7):

se training.rgy Metab-

s following-460.xercise on.uchard C.

to exercise2;112:892-

A, Ray CA.icine posi-

ncreases inn. Med Sci

804 Rivera-Brown and Frontera PRINCIPLES OF EXERCISE PHYSIOLOGY

6. Kenney WL, Wilmore JH, Costill DL. Physiology of Sport an5th ed. Champaign, IL: Human Kinetics; 2011.

7. Spriet LL, Howlett RA. Metabolic control of energy producphysical activity. In: Lamb DR, Murray R, eds. PerspectivesScience and Sports Medicine: The Metabolic Basis of PerforSport. Vol 12. Carmel, IN: Cooper Publishing; 1999, 1-51.

8. Weibel ER. The Pathway for Oxygen. Cambridge, MA: Harvsity Press; 1984.

9. Jacobs RA, Rasmussen P, Siebenmann C, et al. Determinatrial performance and maximal incremental exercise in higendurance athletes. J Appl Physiol 2011;111:1422-1430.

10. Rowell LB. Human Cardiovascular Control. New York, NUniversity Press; 1993.

11. American College of Sports, Medicine. ACSM’s Guidelines fTesting and Prescription. 8th ed. Philadelphia, PA: Lippinco& Wilkins; 2008.

12. Gledhill N, Cox D, Jamnik R. Endurance athletes’ stroke vnot plateau: Major advantage is diastolic function. Med Sci S1994;26:1116-1121.

13. MacDougall JD. Blood pressure responses to resistive, statnamic exercise. In: Fletcher GF, ed. Cardiovascular Responcise. New York NY: American Heart Association; 1994, 15

14. Sesso HD, Paffenbarger RS Jr, Lee IM. Physical activity anheart disease in men: The Harvard Alumni Health Study.2000;102:975-980.

15. Bouchard C, An P, Rice T, et al. Familial aggregation oresponse to exercise training: Results from the HERITAStudy. J Appl Physiol 1999;87:1003-1008.

16. McArdle WD, Katch FI, Katch VL. Essentials of Exercise3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins;

17. Laughlin MH. Cardiovascular response to exercise. Am J Ph277:S244-259.

18. Rowell LB. Human Circulation. New York, NY: OxfordPress; 1986, 137-256.

19. Jackson AS, Beard EF, Wier LT, Ross RM, Stuteville JEChanges in aerobic power of men, ages 25-70 yr. Med Sci S1995;27:113-120.

20. Jackson AS, Wier LT, Ayers GW, Beard EF, Stuteville JEChanges in aerobic power of women, ages 20-64 yr. MedExerc 1996;28:884-891.

21. Trappe SW, Costill DL, Vukovich MD, Jones J, Melham T. Aelite distance runners: A 22-yr longitudinal study. J Ap1996;80:285-290.

22. Bouchard C, Dionne FT, Simoneau JA, Boulay MR. Genetic

and anaerobic performances. Exerc Sport Sci Rev 1992;20:27-58.

ise.

ringciseand

ver-

imened

ord

ciseams

oeserc

dy-xer-

arytion

axily

gy.

99;

sity

SN.erc

SN.orts

ongsiol

bic

23. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain Sfeld NS. Exercise and fluid replacement. American CollegMedicine position stand. Med Sci Sports Exerc 2007;39:37

24. Coyle EF, Hamilton M. Fluid replacement during exercise:physiological homeostasis and performance. In: Gisolfi CV, LamPerspectives in Exercise Science and Sports Medicine: Fluid HDuring Exercise. Vol 3. Carmel, IN: Cooper Publishing; 1990

25. Rivera-Brown AM, De Felix-Dávila RA. Hydration status injudo athletes before and after training in the heat. Int J SpoPerform 2012;7:39-46.

26. Judelson DA, Maresh CM, Anderson JM, et al. Hydration anperformance: Does fluid balance affect strength, powerintensity endurance? Sports Med 2007;37:907-921.

27. Layzer RB. The origin of muscle fasciculations and cramNerve 1994;17:1243-1249.

28. US Department of Health and Human Services. 2008 PhysiGuidelines for Americans; 2008. Available at http://www.paguidelines/guidelines/default.aspx. Accessed October 13,

29. Timmons JA, Knudsen S, Rankinen T, et al. Using moleculation to predict gains in maximal aerobic capacity followingexercise training in humans. J Appl Physiol 2010;108:1487

30. Laughlin MH, Roseguini B. Mechanisms for exercise traininincreases in skeletal muscle blood flow capacity: Differinterval sprint training versus aerobic endurance trainingPharmacol 2008;59(Suppl 7):71-88.

31. Holloszy JO. Regulation by exercise of skeletal musclemitochondria and GLUT4. J Physiol Pharmacol 2008;595-18.

32. Holloszy JO. Metabolic consequences of endurance exerciIn: Horton ES, Terjung RJ, eds. Exercise, Nutrition, and Eneolism. New York, NY: Macmillan; 1988.

33. Goodman JM, Liu PP, Green HJ. Left ventricular adaptationshort-term endurance training. J Appl Physiol 2005;98:454

34. Carter JB, Banister EW, Blaber AP. Effect of endurance eautonomic control of heart rate. Sports Med 2003;33:33-46

35. Rankinen T, Sung YJ, Sarzynski MA, Rice TK, Rao DC, BoHeritability of submaximal exercise heart rate responsetraining is accounted for by nine SNPs. J Appl Physiol 201897.

36. Pescatello LS, Franklin BA, Fagard R, Farquhar WB, Kelley GExercise and hypertension. American College of Sports Medtion stand. Med Sci Sports Exerc 2004;36:533-553.

37. Murias JM, Kowalchuk JM, Paterson DH. Mechanisms for iVO max with endurance training in older and young wome

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Sports Exerc 2010;42:1891-1898.