NUTRITION IN SPORT

VOLUME VII OF THE ENCYCLOPAEDIA OF SPORTS MEDICINE

AN IOC MEDICAL COMMISSION PUBLICATION

IN COLLABORATION WITH THE

INTERNATIONAL FEDERATION OF SPORTS MEDICINE

EDITED BY

RONALD J. MAUGHAN

NUTRITION IN SPORT

IOC MEDICAL COMMISSION

SUB-COMMISSION ON PUBLICATIONS IN THE SPORT SCIENCES

Howard G. Knuttgen PhD (Co-ordinator)Boston, Massachusetts, USA

Francesco Conconi MDFerrara, Italy

Harm Kuipers MD, PhDMaastricht, The Netherlands

Per A.F.H. Renström MD, PhDStockholm, Sweden

Richard H. Strauss MDLos Angeles, California, USA

NUTRITION IN SPORT

VOLUME VII OF THE ENCYCLOPAEDIA OF SPORTS MEDICINE

AN IOC MEDICAL COMMISSION PUBLICATION

IN COLLABORATION WITH THE

INTERNATIONAL FEDERATION OF SPORTS MEDICINE

EDITED BY

RONALD J. MAUGHAN

© 2000 byBlackwell Science LtdEditorial Offices:Osney Mead, Oxford OX2 0EL25 John Street, London, WC1N 2BL23 Ainslie Place, Edinburgh EH3 6AJ350 Main Street, Malden

MA 02148 5018, USA54 University Street, Carlton

Victoria 3053, Australia10, rue Casimir Delavigne

75006 Paris, France

Other Editorial Offices:Blackwell Wissenschafts-Verlag GmbHKurfürstendamm 5710707 Berlin, Germany

Blackwell Science KKMG Kodenmacho Building7–10 Kodenmacho NihombashiChuo-ku, Tokyo 104, Japan

The right of the Author to beidentified as the Author of this Workhas been asserted in accordancewith the Copyright, Designs andPatents Act 1988.

All rights reserved. No part ofthis publication may be reproduced,stored in a retrieval system, ortransmitted, in any form or by anymeans, electronic, mechanical,photocopying, recording or otherwise,except as permitted by the UKCopyright, Designs and Patents Act1988, without the prior permissionof the copyright owner.

First published 2000

Set by Excel Typesetters Co., Hong KongPrinted and bound in Great Britainat MPG Books Ltd, Bodmin, Cornwall

The Blackwell Science logo is atrade mark of Blackwell Science Ltd,registered at the United KingdomTrade Marks Registry

Part title illustrations by Grahame Baker

distributors

Marston Book Services LtdPO Box 269Abingdon, Oxon OX14 4YN(Orders: Tel: 01235 465500

Fax: 01235 465555)

USABlackwell Science, Inc.Commerce Place350 Main StreetMalden, MA 02148 5018(Orders: Tel: 800 759 6102

781 388 8250Fax: 781 388 8255)

CanadaLogin Brothers Book Company324 Saulteaux CrescentWinnipeg, Manitoba R3J 3T2(Orders: Tel: 204 837-2987)

AustraliaBlackwell Science Pty Ltd54 University StreetCarlton, Victoria 3053(Orders: Tel: 3 9347 0300

Fax: 3 9347 5001)

A catalogue record for this titleis available from the British Library

ISBN 0-632-05094-2

Library of CongressCataloging-in-publication Data

Nutrition in sport/edited by Ronald J. Maughan.p. cm. — (Encyclopedia of sports medicine; ISSN

v .7)‘An IOC Medical Commission publication in collabora-

tion with the International Federation of Sports Medicine.’ISBN 0-632-05094-21. Nutrition. 2. Energy metabolism. 3. Exercise —

Physiological aspects. 4. Athletes — Nutrition.I. Maughan, Ronald J. II. IOC Medical Commission.III. International Federation of Sports Medicine.IV. Series.QP141.N793 1999616.3¢9¢0088796 — dc21 99-12066

CIP

For further information onBlackwell Science, visit our website:www.blackwell-science.com

Contents

9 Amino Acid Metabolism in Exercise, 119a.j.m. wagenmakers

10 Effects of Exercise on Protein Metabolism, 133p.w.r. lemon

11 Amino Acids, Fatigue and Immunodepression in Exercise, 153e.a. newsholme and l.m. castell

12 Nutrition, Neurotransmitters and CentralNervous System Fatigue, 171j.m. davis

13 Fat Metabolism during Exercise, 184j.a. hawley, a.e. jeukendrup andf. brouns

14 Adaptations to a High Fat Diet, 192b. kiens and j.w. helge

15 Temperature Regulation and Fluid andElectrolyte Balance, 203r.j. maughan and e.r. nadel

16 Effects of Dehydration and Rehydration onPerformance, 216m.n. sawka, w.a. latzkaand s.j. montain

17 Water and Electrolyte Loss and Replacement in Exercise, 226r.j. maughan

List of Contributors, ix

Forewords, xiii

Preface, xv

Part 1: Nutrition and Exercise

1 Basic Exercise Physiology, 3h.g. knuttgen

2 Biochemistry of Exercise, 17m. gleeson

3 Exercise, Nutrition and Health, 39a.e. hardman

4 Energy Costs of Exercise and Sport, 53h.j. montoye

5 Dietary Carbohydrates, 73l.m. burke

6 Carbohydrate Metabolism in Exercise, 85e. hultman and p.l. greenhaff

7 Optimization of Glycogen Stores, 97j.l . ivy

8 Carbohydrate Replacement during Exercise, 112m. hargreaves

v

18 Gastrointestinal Function and Exercise, 241n.j. rehrer and d.f. gerrard

19 Rehydration and Recovery after Exercise, 256s.m. shirreffs

20 Vitamins: Metabolic Functions, 266m. fogelholm

21 Vitamins: Effects of Exercise on Requirements, 281j. chen

22 Exercise-induced Oxidative Stress andAntioxidant Nutrients, 292c.k. sen, s. roy and l. packer

23 Minerals: Calcium, 318k.p. aulin

24 Minerals: Iron, 326e.r. eichner

25 Trace Minerals, 339p.m. clarkson

26 Nutritional Ergogenic Aids, 356m.h. williams andb.c. leutholtz

27 Creatine, 367p.l. greenhaff

28 Caffeine, 379l.l. spriet and r.a. howlett

29 Bicarbonate and Citrate, 393l.r. mcnaughton

30 Alcohol in Sport, 405l.m. burke and r.j. maughan

Part 2: Special Considerations

31 The Female Athlete, 417k.a. gabel

vi contents

32 The Young Athlete, 429v.b. unnithan anda.d.g. baxter-jones

33 The Vegetarian Athlete, 442j.r. berning

34 The Diabetic Athlete, 457j. jensen and b. leighton

Part 3: Practical Issues

35 The Overweight Athlete, 469m.m. manore

36 The Travelling Athlete, 484a.c. grandjean and j.s . ruud

37 Overtraining: Nutritional Intervention, 492h. kuipers

38 Exercise at Climatic Extremes, 497m.a. febbraio

39 Eating Disorders in Athletes, 510j. sundgot-borgen

40 Sports Nutrition Products, 523r. murray

Part 4: Sport-specific Nutrition

41 Sprinting, 535c.w. nicholas

42 Distance Running, 550j.a. hawley, e.-j. schabortand t.d. noakes

43 Cycling, 562a.e. jeukendrup

44 Team Sports, 574j. bangsbo

45 Gymnastics, 588d. benardot

46 Swimming, 609r.l. sharp

47 Weightlifting and Power Events, 621v.a. rogozkin

48 Racquet Sports, 632m. hargreaves

49 Weight Category Sports, 637j.h. wilmore

50 Skating, 646a.c. snyder and c. foster

51 Cross-country Skiing, 656b. ekblom and u. bergh

Index, 663

contents vii

List of Contributors

P.M. CLARKSON PhD, Department of ExerciseScience, University of Massachusetts, Amherst, Mass-achusetts 01003, USA

J .M. DAVIS PhD, Department of Exercise Science,University of South Carolina, Columbia, South Carolina29209, USA

E.R. EICHNER MD, Section of Hematology (EB-271), University of Oklahoma, Health Sciences Center,Oklahoma City, Oklahoma 73190, USA

B. EKBLOM MD, Department of Physiology andPharmacology, Karolinska Institute, Stockholm, Sweden

M.A. FEBBRAIO PhD, Exercise Physiology and Metabolism Laboratory, Department of Physiology, University of Melbourne, Parkville 3052,Australia

M. FOGELHOLM ScD, University of Helsinki,Lahti Research and Training Centre, Saimaankatu 11,15140 Lahti, Finland

C. FOSTER PhD, Department of Exercise and SportScience, University of Wisconsin-La Crosse, La Crosse,Wisconsin 54601, USA

K.A. GABEL PhD, RD, School of Family and Consumer Sciences, College of Agriculture, University ofIdaho, Moscow, Idaho 8344-3183, USA

D.F. GERRARD MB, ChB, Dunedin School ofMedicine, PO Box 913, University of Otago, Dunedin,New Zealand

M. GLEESON PhD, School of Sport and Exercise

K.P. AULIN MD, PhD, Department of Medical Sciences, University of Uppsala; Institute of Sport Sciences, Dalarna University, S-79188 Falun, Sweden

J . BANGSBO PhD, Department of Human Physiology, August Krogh Institute, University ofCopenhagen, 13 Universitetsparken, DK-2100 Copenhagen, Denmark

A.D.G. BAXTER-JONES PhD, Departmentof Child Health, University of Aberdeen, Foresterhill,Aberdeen AB25 2ZD, UK

D. BENARDOT PhD, Center for Sports MedicineScience and Technology, Georgia State University,Atlanta, Georgia 30303, USA

U. BERGH PhD, Defence Research Establishment,17290 Stockholm, Sweden

J .R. BERNING PhD, Department of Biology, Uni-versity of Colorado at Colorado Springs, 1420 AustinBluffs Parkway, Colorado Springs, Colorado 80933, USA

F. BROUNS PhD, Department of Human Biology,Maastricht University, 6200 MD Maastricht, TheNetherlands

L.M. BURKE PhD, Australian Institute of Sport,PO Box 176, Belconnen, Australian Capital Territory2616, Australia

L.M. CASTELL MSc, University Department ofBiochemistry, South Parks Road, Oxford OX1 3QU, UK

J. CHEN MD, Institute of Sports Medicine, BeijingMedical University, Beijing 100083, China

ix

Sciences, University of Birmingham, Birmingham B152TT, UK

A.C. GRANDJEAN Ed.D, International Centerfor Sports Nutrition, Center for Human Nutrition, 502 South 44th Street, Omaha, Nebraska 68105-1065,USA

P.L. GREENHAFF PhD, School of BiomedicalSciences, Queens Medical Centre, Nottingham NG72UH, UK

A.E. HARDMAN PhD, Department of PhysicalEducation, Sports Science and Recreation Management,Loughborough University, Loughborough LE11 3TU, UK

M. HARGREAVES PhD, School of Health Sci-ences, Deakin University, Burwood 3125, Australia

J .A. HAWLEY PhD, Department of HumanBiology and Movement Science, Faculty of Biomedicaland Health Science, RMIT University, PO Box 71, Bundoora, Victoria 3083, Australia

J .W. HELGE PhD, Copenhagen Muscle ResearchCentre, August Krogh Institute, University of Copen-hagen, 13 Universitetsparken, DK-2100 Copenhagen,Denmark

R.A. HOWLETT PhD, Department of Medicine,University of California-San Diego, La Jolla, California92093-0623, USA

E. HULTMAN MD, Department of Medical Labora-tory, Science and Technology, Division of Clinical Chem-istry, Hiddinge University Hospital, KarolinskaInstitute, S-14186 Huddinge, Sweden

J .L. IVY PhD, Exercise Physiology and MetabolismLaboratory, University of Texas at Austin, Belmont Hall, Austin, Texas 78712, USA

J . JENSEN PhD, Department of Physiology, NationalInstitute of Occupational Health, PO Box 8149 Dep, N-0033 Oslo, Norway

A.E. JEUKENDRUP PhD, School of Sport andExercise Sciences, University of Birmingham, Birmingham B15 2TT, UK

x list of contributors

B. KIENS PhD, Copenhagen Muscle Research Centre,August Krogh Institute, University of Copenhagen, 13Universitetsparken, DK-2100 Copenhagen, Denmark

H.G. KNUTTGEN PhD, Department of PhysicalMedicine and Rehabilitation, Harvard University andSpaulding Rehabilitation Hospital, 125 Nashua Street,Boston, Massachusetts 02114-1198, USA

H. KUIPERS MD, Department of Movement Sci-ences, Maastricht University, PO Box 616, Maastricht6200 MD, The Netherlands

W.A. LATZKA ScD, US Army Research Instituteof Environmental Medicine, Kansas Street, Natick, Mass-achusetts 01760, USA

B. LEIGHTON PhD, Zeneca Pharmaceuticals,Alderley Park, Macclesfield SK10 4TG, UK

P.W.R. LEMON PhD, 3M Centre, University of Western Ontario, London, Ontario N6A 3K7, Canada

B.C. LEUTHOLTZ PhD, Department of ExerciseScience, Physical Education and Recreation, Old Dominion University, Norfolk, Virginia 23529-0196,USA

L.R. McNAUGHTON PhD, Department of LifeScience, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey KT1 2EE, UK

M.M. MANORE PhD, Food and Nutrition Labora-tory, Department of Family Resources, Arizona StateUniversity, Tempe, Arizona 85287-2502, USA

R.J . MAUGHAN PhD, Department of Biochemi-cal Sciences, University Medical School, Foresterhill,Aberdeen AB25 2ZD, UK

S.J . MONTAIN PhD, US Army Research Instituteof Environmental Medicine, Kansas Street, Natick, Mass-achusetts 01760, USA

H.J. MONTOYE PhD, Department of Kinesiology,College of Education, Michigan State University, EastLansig, Michigan 48824-1049, USA

R. MURRAY PhD, Exercise Physiology Laboratory,

Quaker Oats Company, 617 West Main Street, Barrington, Illinois 60010, USA

E.R. NADEL PhD, John B. Pierce Foundation Lab-oratory, Yale University School of Medicine, 290 Con-gress Avenue, New Haven, Connecticut 06519, USA (DrE.R. Nadel unfortunately passed away during publica-tion of this volume)

E.A. NEWSHOLME MA, PhD, DSc, University Department of Biochemistry, South ParksRoad, Oxford OX1 3QU, UK

C.W. NICHOLAS PhD, Department of PhysicalEducation and Sports Science, University of Lough-borough, Loughborough, Leicestershire LE11 3TU, UK

T.D. NOAKES MB, ChB, Sports Science Instituteof South Africa, Newlands, 7800 South Africa

L. PACKER PhD, Department of Molecular and CellBiology, University of California at Berkeley, 251 LifeScience Addition, Berkeley, California 94720-3200, USA

N.J. REHRER PhD, School of Physical Education,PO Box 56, Otago University, Dunedin, New Zealand

V.A. ROGOZKIN PhD, Research Institute ofPhysical Culture, Pr Dinamo 2, St Petersburg 197110,Russia

S. ROY PhD, Department of Molecular and CellBiology, University of California at Berkeley, 251 LifeScience Addition, Berkeley, California 94720-3200, USA

J .S . RUUD MS, RD, Center for Human Nutrition,502 South 44th Street, Omaha, Nebraska 68105-1065,USA

M.N. SAWKA PhD, US Army Research Institute ofEnvironmental Medicine, Kansas Street, Natick, Mass-achusetts 10760, USA

E.-J . SCHABORT MSc, Sports Science Institute ofSouth Africa, Newlands, 7800 South Africa

C.K. SEN PhD, Department of Molecular and CellBiology, University of California at Berkeley, 251 LifeScience Addition, Berkeley, California 94720-3200, USA

R.L. SHARP PhD, Department of Health andHuman Performance, Iowa State University, Ames, Iowa50011-1160, USA

S.M. SHIRREFFS PhD, Department of BiomedicalSciences, University Medical School, Foresterhill,Aberdeen AB25 2ZD, UK

A.C. SNYDER PhD, Department of Human Kinet-ics, University of Wisconsin-Milwaukee, PO Box 413,Milwaukee, Wisconsin 53201, USA

L.L. SPRIET PhD, Department of Human Biologyand Nutritional Sciences, University of Guelph, Guelph,Ontario N1G 2W1, Canada

J . SUNDGOT-BORGEN PhD, Department ofBiology and Sports Medicine, Norwegian University ofSport and Physical Education, Oslo, Norway

V.B. UNNITHAN PhD, Department of Exerciseand Sport Science, University of San Francisco, 2130Fulton Street, San Francisco, California 94117-1080,USA

A.J.M. WAGENMAKERS PhD, Departmentof Human Biology, Maastricht University, PO Box 616,6200 MD Maastricht, The Netherlands

M.H. WILLIAMS PhD, Human PerformanceLaboratory, Old Dominion University, Norfolk, Virginia23529-0196, USA

J .H. WILMORE PhD, Department of Health andKinesiology, Texas A&M University, 158 Read Building,College Station, Texas 77843-2443, USA

list of contributors xi

Forewords

xiii

On behalf of the International Olympic Com-mittee, I should like to welcome Volume VII of the Encyclopaedia of Sports Medicine series.This new volume addresses nutrition in sport.Emphasis is given to the role of proper nutri-tion in enhancing good health, well being and the performance capacity of men and women athletes.

I should like to thank all those involved in thepreparation of this volume whose work is highlyrespected and appreciated by the whole OlympicFamily.Juan Antonio SamaranchMarqués de Samaranch

In planning the year-round conditioning pro-gramme and making the final preparations forcompetition, each athlete must carefully considerfood intake in order to ensure that all tissues andbody systems have available the essential ele-ments for the provision of energy and properfunction. Proper nutrition is also essential for

maintenance of a body mass and compositionappropriate to each sport event.

The new volume, Nutrition in Sport, provides awealth of information on the relationship of themetabolism of carbohydrates, fats and proteinsas well as the important involvement of vitaminsand minerals to success in sports performance.Special consideration is given to optimal per-formance in specific sports events. Emphasis isgiven to the role of proper nutrition in enhanc-ing good health, well being and the performancecapacity of men and women athletes. The editor,Professor Ronald J. Maughan, has recruited over60 of the world’s leading nutritionists and physi-ologists to participate in this project. On behalf of the International Olympic Committee and itsMedical Commission I should like to extend oursincere appreciation to the members of our Sub-commission on Publications in the Sport Sciencesand to Blackwell Science, who have made thepublication of this book possible.Prince Alexandre de MerodeChairman, IOC Medical Commission

Preface

xv

At an international Consensus Conference heldin 1991 at the offices of the International OlympicCommittee in Lausanne, a small group of expertsconducted a comprehensive review of the avail-able information and concluded that ‘Diet sig-nificantly influences athletic performance’. Thisstatement is unequivocal: what we eat and drink,how much we consume and when it is consumedcan all have positive or negative effects on per-formance in training and in competition. For the athlete striving to succeed at the highest level and training to the limits of what can be tolerated, this offers an avenue that cannot beignored. Choosing the right foods will not makethe mediocre performer into a world beater, but apoor choice of diet will certainly prevent all ath-letes from realizing their full potential. This maynot be a major concern for the recreational ath-lete or for the ‘weekend warrior’ who train andcompete for enjoyment and for the health bene-fits that exercise participation confers. For thecommitted athlete, however, there seems littlepoint in taking other aspects of performance seri-ously and neglecting diet.

In spite of the importance of diet for health aswell as for athletic performance, there are manypopular misconceptions, and this reflects in partthe limited availability of reliable information.Until recently, there were few books on sportsnutrition available to the coach and athlete or to the scientist with an interest in this area, butseveral have been published in the last decade.Few of these, however, have encompassed thewhole breadth of the subject from the basic

science to the practical issues that affect trainingand competition. In keeping with the format ofthe previous volumes in this series and with theconcept that is implied by the term encyclopae-dia, this volume has attempted to do that. Itbrings together sports nutrition—the underlyingscience that allows identification of nutritionalgoals—and sports dietetics—the practical appli-cation of that science on an individual basis todefine the eating strategies that will allow athletes to achieve those goals. This aim has been made possible by the enthusiastic participa-tion in the preparation of this book by leadingexperts, including both scientists and practi-tioners, from around the world who have con-tributed to the 51 chapters of this book. In manycases, individual chapters are the result of a col-laborative effort involving authors from morethan one country, bringing a true internationalperspective. This reflects the internationaldimension of science and the sense of sharedpurpose among those who work in this field.Although there is an element of competition inscience, it is not parochial and the knowledge it generates is available to all. The depth andbreadth of the expertise of these authors makesthat knowledge available and serves to empha-size those areas where there is a broad consensusof opinion, and to pinpoint areas of uncertaintywhere more information is required.

The contents of this book are divided into foursections, each emphasizing different aspects ofthe art and science of sports nutrition. The first,and largest, section covers the basic science that

underpins the practice of sports nutrition; thesechapters provide definitive information in theform of comprehensive reviews of specific topics.In the second section, a variety of special situa-tions are considered: this begins the move fromthe underlying science to practical application bybringing together information from differentsources to focus on specific issues that affect per-formance. The second section of the book dealswith the nutritional needs of special populationsand the strategies that must be developed tomeet those needs. The third section focuses on some of the practical issues encountered inworking with élite-level athletes. The finalsection of the book provides a detailed coverageof the specific issues relating to preparing for,and competing in, a wide range of differentsports: this section highlights the diversity ofsport and reminds the reader that the generali-zations that are inevitably made in the pre-

ceding sections must be applied with caution when dealing with individuals competing insports that place very different demands on participants.

The sheer size of this book reflects the breadthand depth of the field of sports nutrition. It is atestimony to the expertise of the authors that theinformation this volume contains is presented in a way that will be useful to those engaged inresearch and teaching as well as being accessibleto those who can benefit most from its practicalapplication. These include exercise scientists andsports physicians, nutritionists and dietitians.Some background knowledge is necessary for a full appreciation of the contents, but theinformed and educated coach and athlete shouldfind much of interest.

Ron Maughan1999

xvi preface

PART 1

NUTRITION AND EXERCISE

Introduction

The performance of sport, as with all physicalexercise, is dependent upon the coordinated acti-vation of the athlete’s skeletal muscles. Themuscles constitute the sources of the forces andpower required for skilled movement. Unfortu-nately, the description and quantification of exer-cise is frequently made awkward, if not difficult,by a variety of terms, some of which are confus-ing or inaccurate. Through the years, terms havebeen regularly misused and units of measure-ment inappropriately applied.

Exercise

The term exercise, itself, has been defined in dif-ferent ways by different sources in the literature.For the Encyclopaedia of Sports Medicine series ofpublications, the definition has been accepted as‘any and all activity involving generation of forceby activated skeletal muscle’ (Komi 1992). Thiswould include activities of daily living, activitiesof labour, activities for physical conditioning andphysical recreation, as well as participation insport competition. In the Encyclopaedia of SportsMedicine series, a sport will be considered as any organized activity that involves exercise,rules governing the event and the element ofcompetition.

To bring about movement of the body partsand coordinate the skills of a sport, the centralnervous system activates the striated, voluntarymuscle cells which are the principal constituents

of the various structures called skeletal muscles.The response of muscle cells to neural stimula-tion is to produce force.

In order to develop force, skeletal muscle cellsare activated by electrochemical impulses arriv-ing via efferent neurones, the cell bodies of whichare located in the anterior horn of the gray matterof the spinal cord. When the threshold of excita-tion of the muscle cells of a motor unit has beenattained, electrochemical events within eachmuscle cell (fibre) result in the cylindrical fibregenerating force along its longitudinal axis inorder to draw the ends of the cylinder towards its midsection. In this way, the activated fibresdevelop force between the attachments of themuscle in which they are contained. It has beenproposed that this process be referred to as amuscle ‘action’ (Cavanagh 1988) rather than‘contraction’ due to the fact that any activatedindividual fibre and, indeed, an entire musclemay: (i) shorten the distance along its longitudi-nal axis, (ii) be held at the same length by anopposing force, or (iii) be forcibly stretched inlength by an opposing force. The term action hasthe advantage of being independent of a changein length or of direction. By definition, contractionmeans shortening only.

The terminology employed to identify thethree actions thus deserves discussion and expla-nation. The interaction of muscle force develop-ment and the external forces will result in actionsthat produce static exercise (no movement aboutthe related joints) or in dynamic exercise (result-ing in a change in joint angles). Static exercise of

Chapter 1

Basic Exercise Physiology

HOWARD G. KNUTTGEN

3

activated muscle is traditionally referred to asisometric. Force is developed but, as there is nomovement, no work is performed. All othermuscle actions involve movement and aretermed dynamic. The term concentric is tradition-ally used to identify a shortening action and theterm eccentric is used to identify a lengtheningaction, although the origin of these terms isobscure (Table 1.1) (Knuttgen & Kraemer 1987).

The International System

Some years ago, the world of science adopted anInternational System of Measurement (BureauInternational des Poids et Mésures 1977; LeSystème International, abbreviated as SI) to quan-tify all physical entities and processes. The unitof force in the SI is the newton (N). One newton isquantified as the force which imparts to a mass of1 kilogram an acceleration of 1 metre per secondper second. To develop force, a muscle cellrequires energy, and the SI unit for energy is thejoule (J).

When force is expressed through a displace-ment (i.e. movement of body parts is occurring),work is measured as force (N) multiplied by thedistance (m) of the displacement, and work canbe calculated as force¥ distance: 1N¥ 1m= 1J.During movement, the performance of workinvolves conversion of one form of energy (J) toanother. The SI unit for energy is the same unitused to quantify work. One joule is the energy of1 newton acting through a distance of 1 metre.

Any energy used by the muscle for force devel-opment that does not result in work becomesheat, the SI unit for heat also being the joule.Obviously, direct relationships exist amongenergy, work and heat and they are quantified

4 nutrition and exercise

with the same unit, the joule. Throughout thispublication, the term energy will most often referto metabolic energy.

When time [SI unit, the second (s)] becomes afactor in quantifying energy release, the perfor-mance of work or the generation of heat, then therate of energy release, work performance or heatgeneration is presented as power, the SI unit forwhich is the watt (W) (1 J¥1 s–1 =1 W). In exercisein which 150 W of external power is produced ata metabolic cost of 750 W, then the rate of heatproduction is 600W.

Attention should be called at this point to thefact that, when describing exercise and sport,physiologists and nutritionists can be interestedin the available energy content that can bemetabolized from the food ingested (J), the totalstored energy available for the muscle cells (J),the total energy utilized during a conditioningsession or sports performance (J), or the rate atwhich muscle cells are called upon to producepower (W).

The joule and the calorie

As described above, the joule is the SI unit usedto quantify energy, work and heat. This providesa simple and efficient basis for describing therelationship among nutrition, exercise perfor-mance, body heat generation and heat dissipa-tion, both in terms of total amounts (in joules) oras power (in watts). Unfortunately, the calorieand its multiple, the kilocalorie (kcal), have beenutilized for so long in nutritional circles that achange to the description of the energy content offoods in joules is being implemented very slowly.Instead of utilizing the convenient relationshipsamong newtons, joules, seconds and watts, conversion factors need to be employed. Forexample, 1cal=4.186 J and 1kcal= 4.186kJ.

When a mechanically braked cycle ergometeris used for an exercise bout, one method ofobtaining the desired power production wouldbe to have the subject cycle at a pace that wouldproduce a ‘velocity’ of the flywheel rim of 5 m·s–1

and provide an opposing force (sometimestermed ‘resistance’) of 60 N. The simplest way of

Table 1.1 Classification of exercise and muscle actiontypes.

Exercise Muscle action Muscle length

Dynamic Concentric DecreasesDynamic Eccentric IncreasesStatic Isometric No change

quantifying exercise is with SI units. The bout ofexercise can be described as follows:

Power developed on the ergometer: 300W

Duration of exercise: 600 s (10 min)

Metabolic power (derived from oxygen uptake):1500W

Total metabolic energy utilized =1500 W¥ 600s= 900000 J=900 kJ

Mechanical efficiency =300 W/1500 W¥ 100=20%

If work is calculated by using a ‘kilogram offorce’ (an improper unit of measurement!), akilogram-metre can be utilized as an unsanc-tioned unit to quantify work. Conversion factorswould be utilized to convert kilogram-metresper unit of time into the correct unit for power,the watt. If the calorie is used to quantify meta-bolic energy, conversion factors must be utilizedto obtain a measurement of metabolic power thatcan be compared to the power transferred to thecycle ergometer. It is far easier to utilize SI unitsthroughout all research activity and scientificwriting: the newton, the metre, the second, thejoule and the watt. (It is important to call atten-tion to the fact that a kilogram-metre [kg-m] inthe SI is actually the correct unit of measurementfor torque.)

There are an infinite number of configurationsof force and velocity (determined by cadence onthe ergometer) that can produce the desiredexternal power produced and therefore meta-bolic power desired.

In this volume, the editorial decision wasmade to acknowledge the continued and exten-sive use of the kilocalorie (kcal) in much of thescientific literature for the quantification of theenergy content of foods and therefore to permitthe use of this unit of measurement in the variouschapters where considered expedient.

Energy for muscle activity

The mechanical and biochemical events associ-ated with muscle cell force development are

described in detail in Chapter 2. However, it isworth making the following general commentsand observations as related to nutrition for sport.

The immediate source of energy for muscleforce and power production is adenosinetriphosphate (ATP). ATP is the final biochemicalcarrier of energy to the myofilaments for the gen-eration of force. The breakdown of phosphocrea-tine (PCr) serves to reconstitute ATP when othersources contribute little or no energy. Eachmuscle cell then becomes dependent on fat (fattyacids), carbohydrate (glucose and glycogen) and,to a very limited extent, protein (amino acids) asthe sources of energy to resynthesize ATP andPCr during exercise. All persons concerned withthe nutrition of the athlete must consider thenutritional demands of the long-term condition-ing programme, the preparation for competitionand the competitive event itself, when planningindividual meals as well as the weekly andmonthly dietary programmes.

It is generally accepted that the muscle cellsobtain all the energy needed for short-term sportperformance of a few seconds (as in the throwingand jumping events of track and field, weight-lifting and springboard and platform diving)from ATP and PCr (Fig. 1.1). These compoundsare then resynthesized during recovery. When asport performance lasts approximately 10 s (e.g.the 100-m run), other energy sources, includingespecially anaerobic glycolysis (resulting in lacticacid formation in the muscle), must also con-tribute to the resynthesis of ATP. The lower theintensity and the longer the event, the better ableis aerobic glycolysis to contribute energy. It isalso assumed that, during events that are stillconsidered ‘sprints’ but that last longer than afew seconds, aerobic metabolism begins to makea contribution to ATP resynthesis.

As the duration of the exercise periodincreases still further, the energy from the oxida-tion of a combination of fat and carbohydratebecomes a significant source of energy. If exerciselasts 15min or longer, such intensities demand asteady-state of aerobic metabolism (i.e. lowerthan maximum aerobic metabolism) except forany final effort that calls forth all the power the

basic exercise physiology 5

athlete can generate. The final burst of power (or‘kick’) results from a combination of high utiliza-tion of both anaerobic glycolysis and aerobicpower. In the range of events that last between 30s and 12min, a combination of anaerobic gly-colysis and oxidative metabolism provides mostof the energy necessary to resynthesize ATP andpermit the athlete to continue. The lower thedemand for power, the better the oxidativemetabolism can provide the energy for ATPresynthesis. Anaerobic glycolysis involves onlycarbohydrate and, at these high intensities, evenaerobic metabolism draws upon carbohydrate inpreference to fat.

An athlete who performs to exhaustion in approximately 3–12 min challenges the car-diorespiratory and metabolic mechanisms sothat aerobic metabolism eventually attains itshighest level. When this occurs, the oxygenuptake is identified as either ‘maximum oxygenuptake’ (V

.o2max.) or ‘maximum aerobic power’.

It is not uncommon to read and hear the term‘maximum exercise’ used to refer to intensitiesthat result in maximum oxygen uptake. The termis completely misleading, given the fact that theathlete can produce power anaerobically forshort periods of time that is four to five times asgreat as that which can be developed utilizingmaximum aerobic power.

Fat is stored to a limited extent inside the

6 nutrition and exercise

muscle cells but can be mobilized during exercisefrom depots around the body for transport by thecirculatory system to active muscle cells. Carbo-hydrate is stored inside the muscle cells as glyco-gen but can also be mobilized as glucose fromglycogen stored in the liver.

Power, energy and endurance

The information presented in the three panels ofFig. 1.2 provides vivid examples of the relation-ships among human metabolic power produc-tion, the sources of energy and the ability toendure at specific exercise intensities. In panel A,the relationship between endurance (or time toexhaustion) is plotted vs. metabolic power. Forthe sample athlete, power production of about5000W can be assumed to come solely fromenergy stored in skeletal muscle ATP and PCr.

In the range of 2000–4000W, anaerobic glyco-lysis assumes major responsibility for the provi-sion of energy. This results in the production oflarge amounts of lactic acid and lowered pH inthe sarcoplasm, which are believed to eventuallyhinder force and power development by themuscle fibres. Lactic acid values in the blood risecommensurate with muscle concentrations.

For the athlete in the example, oxidativemetabolism begins to make a major contributionof energy for ATP and PCr resynthesis once the

Fig. 1.1 Olympic weightlifting isan example of a sport in which thecompetitive performance is soshort that all of the energy for thelift is provided by the high-energyphosphates, ATP and PCr. Photo© Allsport.

power output falls to approximately 2000W. It is at power productions of 1500–1800W thatthe maximum oxygen uptake (V

.o2max. of 2.7

mmol · s–1) is elicited for this athlete during thefinal stage of an exercise bout. At 1500 W, theathlete could sustain exercise for approximately8min but at 1800W, for less than 5min.

Below 1500W (Fig. 1.2b), the athlete is able tosustain exercise for extended periods with com-pletely or nearly completely aerobic metabolism,utilizing fat and carbohydrate to resynthesizeATP and PCr. The letter ‘M’ is placed on the

abscissa to indicate the power production corre-sponding to about 75–80% V

.o2max. that the

athlete could sustain for a marathon (42.2 km). Atany higher level, the athlete would enlist anaero-bic glycolysis, accumulate lactate and lower pHvalues in the skeletal muscle cells, and be forced,eventually, to reduce power or stop.

Note the relatively narrow range of power pro-duction that can be produced completely aerobi-cally by comparing Fig. 1.2b with Fig. 1.2a.Marathon pace in this example would constituteapproximately 24% of maximum power produc-

basic exercise physiology 7

*

*

***

*

* *

40

30

20

10

0

End

ura

nce

tim

e to

exh

aust

ion

(m

in)

0 2000 4000 6000

Metabolic power (W)

3

2

1

1.0

0.9

0.8

0.7

100

75

50

25

0

0

25

50

75

100

Rest 500 1000 1500 2000 6000 Rest 500 1000 1500 2000 6000

Metabolic power (W) Metabolic power (W)

M

VO

2 (m

mo

l. s–1

).

RQ

%CHO

%Fat

(a)

(b) (c)

Fig. 1.2 The relationships of (a) endurance time, (b) oxygen uptake in steady state, and (c) respiratory quotient(RQ) and percentage substrate utilization to human metabolic power production. Values presented for power arerepresentative for an 80-kg athlete.

tion and the range for maximum aerobic powerwould constitute approximately 30% of maxi-mum power production (Fig. 1.3).

In Fig. 1.2c, the relationship of respiratory quo-tient (RQ) as determined from steady-state respi-ratory exchange ratio (RER) to metabolic poweris presented. RER, which compares oxygenuptake to carbon dioxide removal in the lungs,attains steady state at lower levels of power pro-duction (in this example, less than 1500 W). Thevalues for RQ vs. power production are modifiedfrom Åstrand and Rodahl (1986). A range is pre-sented to accommodate different values thatmight be obtained during different days as aresult of variations in the athlete’s diet. Utilizingboth the left-side and the right-side ordinates, theobserved RQs indicate a high utilization of car-bohydrate from approximately 75% of maximumaerobic power and upwards. The higher the intensity, the greater is the contribution ofcarbohydrate.

An athlete maintaining a diet high in carbohy-drate will maintain a higher RQ at all levels ofaerobic exercise, whereas the RQ of an athletewith a low intake of carbohydrate will remainremarkably lower. During long-lasting eventsand training bouts, the RQ will become lower atany chosen intensity the longer the exercise lasts,as it is related to increasing free fatty acid avail-

8 nutrition and exercise

ability and falling levels of glycogen in the activemuscles. RQ can also be affected by the ingestionof a substance such as caffeine which results in anenhanced utilization of fatty acids for the energydemands of exercise.

Skeletal muscle

A skeletal muscle is made up predominantly ofextrafusal skeletal muscle fibres, long cylindricalcells which run the length of the muscle, be itshort or long (e.g. 1–300mm). Intrafusal fibresare the small skeletal muscle cells found in themuscle spindles which assist in controlling thebody’s coordinated movement. The muscle alsoincludes connective tissue which provides someorganization to the muscle’s internal structure(white connective tissue) and elasticity (yellowconnective tissue). Arteries, veins and capillariesmade up of smooth muscle, connective tissueand epithelial cells are found throughout eachmuscle, serving as the combination delivery/removal system. Afferent and efferent neuronesconnect each muscle to the central nervoussystem to provide the muscle with motor controland send sensory information to the centralnervous system. Fat is found within and betweenmuscle cells in quantities that become reflected inthe person’s total body composition and percent-

Fig. 1.3 Marathon pace for arunner requires approximately75–80% of maximal aerobic powerand approximately 24% of theanaerobic power the samemuscles could produce for astrength exercise. Photo © NOPP / Larry Bessel.

age body fat. Therefore, each muscle is made upof cells representing the four basic tissue groups:muscle, connective, nervous and epithelial.

Extrafusal fibres can be further divided amonggroups based upon the interrelated twitch char-acteristics and metabolic capabilities. Fibres of a particular motor unit (defined as a motorneurone together with the extrafusal fibres itinnervates) that attain peak force developmentrelatively slowly are routinely termed ‘slowtwitch’ or type I fibres. Fibres that attain peakforce relatively more rapidly are termed ‘fasttwitch’ or type II fibres and further subdividedinto type IIa, type IIab and type IIb groups, asbased on myosin ATPase staining (Fig. 1.4).

Type I fibres are characterized by high mito-chondrial density, high myoglobin content, highaerobic metabolism and modest glycolytic capac-ity. Early anatomists described muscles withwhat we now identify as high type I fibre popula-tion as ‘red muscle’ because of the darker colourcaused by the high myoglobin content. Type IIfibres have high glycolytic capability, low mito-chondrial density and low capacity for aerobicmetabolism. Types IIa, IIab and IIb fibres are lowin myoglobin content, the reason for their beingidentified many decades ago as white musclefibres.

The total number of muscle fibres in a particu-

lar muscle and the proportion identified as type Iand type II appear to be genetically dominated,with small changes occurring through condition-ing, injury, ageing, etc. It should also be men-tioned that, while type II motor units are termedfast twitch and type I motor units are termedslow twitch, the comparison is on relative termsand all extrafusal muscle fibres attain peak forceand shorten extremely fast. The differencesamong them are great, however, and the shorten-ing velocity is generally considered to be 4–10times faster for the type II fibres than for type Ifibres.

The maximum force that can be developed byan activated muscle is directly related to thephysiological cross-section of the muscle, a termthat describes the collective cross-sectional areaof the muscle cells, excluding the connectivetissue (including fat), nervous tissue and bloodvessels. The larger the physiological cross-section of muscle, the greater is the muscle’sability to generate peak force (strength). Consid-erable evidence exists to confirm the importanceof the type II fibre population of a muscle to itsability to develop high force and power.

A high type I fibre population and the accom-panying increased capillarization to supplyoxygen has been shown to be important for sus-tained, rhythmic exercise which depends on

basic exercise physiology 9

Fig. 1.4 Cross-section of humanmuscle showing the mosaicpattern of fibres: darkest stain =type I; lightest stain = type IIa;medium light stain = type IIab;medium dark stain = type IIb.Photo courtesy of William J.Kraemer.

aerobic metabolism. For example, a marathonrunner can utilize over 12000 repeated muscleactions of each leg in completing the 42.2-kmcourse.

The characteristics and capabilities of themuscle fibres can be substantially modified byspecific training programmes. Athletes engagingin sports which involve wide ranges of powerand continuously varying amounts of aerobicand anaerobic metabolism must utilize a pro-gramme of conditioning that raises both theanaerobic and aerobic capabilities of the threefibre types. Examples of such sports are soccer,basketball and tennis.

Physiological support systems

While muscle cells may obtain energy for forceand power production from both anaerobicsources (the breakdown of ATP and PCr; anaero-bic glycolysis) and aerobic sources (aerobic gly-colysis and b-oxidation of fatty acids, bothleading to the provision of electrons to the elec-tron transport system in the mitochondria), theentire human organism and all of its componentcells are fundamentally aerobic. Exercise per-formed at low enough intensities can be per-formed entirely with energy from aerobicmetabolism. The provision of significantamounts of energy for muscular activity by theanaerobic mechanisms, however, is limited inamount and therefore in time. Most importantly,the return to the pre-exercise or resting state following any amount of anaerobic energyrelease is accomplished exclusively by aerobicmetabolism.

Therefore, the essential features in the provi-sion of oxygen for metabolism during aerobicexercise and recovery following anaerobic exer-cise become pulmonary ventilation (air move-ment into and out of the lungs), externalrespiration (exchange of O2 and CO2 betweenalveoli and pulmonary capillary blood), bloodcirculation and internal respiration (exchange ofO2 and CO2 between systemic capillary bloodand interstitial fluid). The essential elements asregards these processes are cardiac output, blood

10 nutrition and exercise

volume, blood composition and skeletal musclecapillarization.

Pulmonary ventilation and external respiration

Movement of air into and out of the lungs isaccomplished by the diaphragm and variousmuscles of the neck and trunk. Pulmonary venti-lation is usually accomplished as a subconsciousactivity under the influence of chemical stimuliprovided by the systemic arterial blood to anervous centre in the brain stem. While thiscentre serves the sole function of controlling theminute volume of pulmonary ventilation (byinteraction of frequency of ventilation and mag-nitude of tidal volume), it is interesting to notethat it is identified anatomically and physiologi-cally as the ‘respiratory centre.’

For continuous aerobic activity that wouldinvolve attainment of a ‘steady state’ of oxygenuptake (and carbon dioxide elimination) via the lungs, pulmonary ventilation correspondsdirectly to oxygen uptake by an approximate 20 : 1 ratio (litres per minute are used in the presentation of both variables). Starting at rest,an 80-kg athlete would expect the values pre-sented in Table 1.2 for oxygen uptake and pul-monary ventilation.

The increase in the ratio for the highest level ofactivity reflects the increased acidity of the blooddue to the production in the muscle and appear-

Table 1.2 Representative data for steady-state oxygenuptake and ventilatory minute volume at rest andduring various intensities of constant-intensityexercise (for an 80-kg athlete). The maximum aerobicpower is 4.5 l · min-1.

V.

o2 V.

E(l · min-1) (l · min-1)

Rest 0.25 5-- 1.00 20-- 2.00 40-- 3.00 60Intense aerobic exercise 3.50 70Intense aerobic exercise with 4.00 100

anaerobic contribution

ance in the blood of lactic acid, as related to theanaerobic metabolism.

For the athlete performing aerobic exerciseunder most conditions, it is considered that theindividual’s capacity for ventilation is adequateto provide O2 from the atmosphere to the alveoliand to carry CO2 from the alveoli to the atmos-phere. In elite endurance athletes who are highlyconditioned for aerobic metabolism and are per-forming near their capacities for aerobic powerproduction, it can be frequently observed thatblood leaving the lungs via the pulmonary veinsis not as saturated with oxygen as it is under theconditions of rest and submaximal aerobic exer-cise. It can thus be concluded that, under the veryspecial conditions where a very highly condi-tioned athlete is performing high-intensityaerobic exercise, pulmonary ventilation serves asa limiting factor for external respiration andtherefore oxygen uptake.

Circulation

For the delivery of oxygen, the removal of carbondioxide and the transport of anabolites andcatabolites to and from the body cells, the organ-ism is dependent upon the circulation of theblood. With regard to the aerobic metabolismrelated to exercise and recovery, the most impor-tant factors are: the oxygen-carrying capacity ofthe blood, the blood volume available, the abilityof the heart to pump blood (cardiac output) andthe capillarization of the skeletal muscles.

The term cardiac output can actually refer to theamount of blood ejected through the aorta or thepulmonary arteries per minute (‘minute volume’or Q

.) or the amount of blood ejected per sys-

tole (‘stroke volume’ or SV). The relationshipbetween minute volume and stroke volumeincludes the contraction frequency of the heart(fH) as follows: Q

.= fH ·SV.

The relationship of these variables withoxygen uptake includes the unloading factor ofoxygen in the tissues as determined from thecontent of oxygen in systemic arterial blood(Cao2) and the content in systemic mixed venousblood (Cvo2). It is:

V.o2 = fH · SV ·a-vo2diff.

Representative values for an 80-kg athlete arepresented in Table 1.3. It can be observed that therelationship between aerobic power (oxygenuptake) and heart rate is essentially rectilinear.Stroke volume increases from a resting value of104ml to near maximum values even duringlow-intensity aerobic exercise. The increase incardiac minute volume as higher levels ofoxygen uptake are attained is accounted for bythe increase in heart rate.

Meanwhile, the arteriovenous oxygen differ-ence continues to increase due solely to thelowered concentration of oxygen in systemicmixed venous blood leaving the active tissues.The arterial concentration remains constant at avalue of approximately 20 ml · l–1 blood, indicat-ing that pulmonary capillary blood becomes

basic exercise physiology 11

Table 1.3 Representative data for steady-state oxygen uptake and circulatory variables at rest and during variousintensities of constant-intensity exercise (for an 80-kg athlete). The maximum aerobic power for the athlete is 4.5 l · min-1 and maximum fH is 195.

V.

o2 Q.

fH a-vo2diff.(l · min-1) (l · min-1) (beats · min-1) SV (ml) (ml O2 · l-1)

Rest 0.25 6.4 60 104 40-- 1.00 12.3 100 123 81-- 2.00 14.8 120 123 136-- 3.00 17.2 140 123 174Intense aerobic exercise 3.50 19.7 160 123 178Intense aerobic exercise with 4.00 22.1 180 123 180

anaerobic contribution

completely saturated with O2 obtained from the alveoli. It should be noted that, at the high-est levels of oxygen uptake, highly trainedendurance athletes (e.g. distance runners andcross-country skiers) show a lowered oxygensaturation in arterial blood. This is taken to indi-cate that the blood flow through the lungs duringsuch intense aerobic exercise for these athletesexceeds the capacity of the ventilatory system toprovide oxygen to the lungs.

As will be discussed, maximum aerobic power(V

.o2max.) can be increased mainly by increasing

the stroke volume capability of the heart, which increases the minute volume capability.Maximum heart rate does not increase withaerobic conditioning but, actually, it eitherremains the same or decreases.

The V.o2max. of 4.5 l · min–1 corresponds to a

metabolic power production of 1500 W. As theathlete in the example is capable of power pro-duction for short periods (e.g. 1–20s) in the rangeof 3000–6000W, the question could be raised as towhat values for the circulatory variables wouldbe expected during such exercise performance.The answer is that these values, if measured,would be irrelevant. The athlete would be per-forming in the range of power production whereoxidative (aerobic) metabolism contributes littleor no energy and the muscles will rely on ATP,PCr and anaerobic glycolysis.

Adaptations to conditioning

The adaptations of the human organism to pro-grammes of exercise conditioning are highly spe-cific to the exercise programme (i.e. the stimulus)provided. Adaptations to resistance training forstrength, to anaerobic training (as in sprinting)and to endurance (aerobic) training are very dif-ferent and, if used inappropriately, can actuallyserve to be counterproductive.

Aerobic conditioning

For athletes engaged in events lasting approxi-mately 3min or longer, aerobic conditioning is acrucial factor in preparing for competition (Fig.

12 nutrition and exercise

1.5). For events lasting between 1 and 3 min,aerobic conditioning is important but anaerobicsources of energy for the power demandsbecome more important the higher the exerciseintensity and the shorter the accompanying per-formance time. It also makes a great differencewhether or not the athlete performs to exhaus-tion (such as in the 10-km run) or is involved inone half of a soccer match (45min) whichinvolves a wide range of aerobic/anaerobicintensities and intermittent activity. Also, skillmay be more important than any other perfor-mance consideration.

If an increase in aerobic power is required, theathlete must follow a programme designed toincrease the cardiac output capability (SV and

Fig. 1.5 A sport such as road cycling dependspredominantly upon aerobic metabolism. Photo ©Allsport / M. Powell.