Introduction to Sport Nutrition

1

Sport Nutrition

Introduction to Sport Nutrition

NCSF

Sport Nutrition

Chapter

1

Introduction to Sports Nutrition

The idea of nutrition for sports is by no means novel. Arguably, it dates

back to at least 400 B.C., when Hippocrates linked diet, activity, and human

well-being. In fact, early Olympians consumed a high quantity of meat,

believing that certain foods fueled performance. In addition, Roman

legionaries were fed planned diets in preparation for traveling long distance

or when engaging in specific combat situations as dictated by battle plans.

With this history in mind, however, modern nutritional science dates back

less than 100 years, beginning with the isolation of the first vitamin, thi-

amine (B1) in 1926. The following decades focused on the discovery of the

micronutrient deficiencies associated with certain medical conditions. This

progress was followed by single-nutrient focused (e.g., saturated fat, low fat,

sugar) investigations, the introduction of fortified foods, and malnutrition

research, which eventually evolved to our contemporary emphasis on diet

quality (7). Thus, the current knowledge supporting elite athletes’ dietary practices stems from

the information collected and analyzed in the last century.

Interestingly, the consumption of various alcoholic beverages during and before competi-

tion was believed to enhance performance, and early Olympians, even in the early 20th century,

used alcohol as an “ergogenic aid” (4, 14). Today, we know its negative effects on performance,

recovery, protein synthesis, metabolism, and the nervous system (11, 12). During the 20th century,

novel investigations analyzed macronutrients relations to performance. One of the first studies

in the era of modern nutritional science analyzed the roles of carbohydrates and fats in pro-

viding energy during exercise, examining the concept of the energy continuum. Today, scientists

still seek to elucidate the effects of the same macronutrients on sports performance by

manipulating the impact of timing, quantity, and nutrient types on different aspects of sports

performance and recovery.

Modern technology and methodology have provided a much better understanding of

biochemistry and the important relationships between nutrients and health, and fitness and

performance; however, much of current practices today do not originate in the lab but arise

from the experimentation of athletes and coaches. Diet modification, competition-specific

practices, and even supplements and ergogenic aids have historical links with sports. However,

with all the modern advancements in science and technology, a definitive diet for sport, fitness,

or health has proved elusive. Genetic diversity, cultural differences, and daily experiences all

present variables to a single dietary strategy for all humans in a homogenous group, athletes

or otherwise.

Even the definition of diet has nuances: does it signify a habitual intake of nutrients or

an acute adjustment to those habits? Do special reasons for specific intakes exist, or are they

associated with a seasonal occurrence, inclusive of nutritional periodization? Seemingly, numer-

ous factors influence the food and drink a given person consumes at a given time. The idea of

sports nutrition includes this concept, as the diet of an athlete or fitness enthusiast may require

adjustments specific to the environment he or she is exposed to and the subsequent internal

Chapter 1 NCSF Sport Nutrition

2

DEFINITIONS

Ergogenic aid –

Any ingested or employed element used for the specific purpose of improving performance.

Supplements –

Dietary product used to supplement a deficiency in the diet (e.g., multi-mineral/vitamin pills).

Introduction to Sport Nutrition

responses that occur with the exposure. But nutrition differs from diet. A diet con-

sists of nutrient and non-nutrient intakes, consumed by the mouth. Nutrition

involves all physiological processes that happen after the food or drink enters

the body to nourish cells and tissues, including responses of the digestive,

endocrine, circulatory, and excretory systems and the resultant metabolism.

Definitions of DIET

a: food and drink regularly provided or consumed

• a diet of fruits and vegetables

• a vegetarian diet

b: habitual nourishment

• links between diet and disease

c: the kind and amount of food prescribed for a person or

animal for a special reason

• was put on a low-sodium diet

d: a regimen of eating and drinking sparingly so as to reduce one’s weight

• going on a diet

A nutrient is a substance that nourishes an organism and

performs one or more functions. Nutrients are classified into two

primary categories: energy-yielding nutrients (EYN) and non-

energy yielding nutrients (NEYN). EYN and NEYN are further

broken down by chemical specificity into carbohydrates, fats, and

proteins, and vitamins, minerals, and water. All humans need

these nutrients for homeostasis; if any nutrient is missing, prob-

lems will exist in one or more of the life pathways. These pathways

tend to be divided into nutrients that promote growth and devel-

opment, provide energy, and regulate metabolic function.

3

NCSF Sport Nutrition Chapter 1


1 Ingestion

2 Digestion

3 Absorption

4 Circulation

5 Assimilation

6 Elimination

Stages ofNutrition

Vitamins Minerals

ENERGY-YIELDING NUTRIENTS NON-ENERGY YIELDING NUTRIENTS

Proteins – amino acids

Fats – fatty acids and glycerol

DEFINITIONS

Nutrient –

Any substance that provides nourishment to the body and helps maintain homeostasis of all bodily systems.

Energy-yielding nutrients –

Nutrients which yield usable energy in the form of calories; in -cludes carbohydrates, protein, and fat (non-nutrient alcohol contains 7 kcal).

Non-energy yielding nutrients –

Nutrients which do not contain calories but are still essential to bodily functions; includes water, minerals and vitamins.

Water

Carbohydrates – glucose, (preferred energy

source) fructose and galactose

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Therefore, a nutritious diet would be defined as one that regularly meets all of the body’s

macronutrient and micronutrient demands. Based on this definition, it would seem easy to

compose a nutritious diet for all humans. However, no single perfect diet exists for everyone.

Whereas domestic animals often eat the same foods every day, humans are omnivorous and

present diverse factors that affect nutritional needs. Certainly, some proposed diets suggest

everyone follow a particular nutrient prescription to attain optimal nutrition and body weight,

but if that were the case, only one diet book and diet would exist. Basic logic would suggest a

250 lb. NFL player would not have the same needs as a 142 lb. Olympic marathoner, even though

they would both qualify as athletes. Correspondingly, dietary strategies for weight loss do not

reflect the same nutrient makeup used for weight gain; even if, broadly speaking, both concern

themselves with the same areas of focus. Therefore, any diet’s nutrient composition should

reflect the goals of the diet as they pertain to health, fitness, and performance.

Eating for health should be simple: consume a variety of nutrients to establish a balance in

nutrition that provides for sufficiency without excess, relative to daily caloric expenditure.

Nonetheless, most people fail to satisfy this basic obligation. Part of the issue lies in the fact that

most people do not know how to put together a balanced diet, and many people are already

overweight and physically inactive, with just as many having one or more diseases. Including

these propositions exposes the complications in what seemed to be a simplistic strategy for all.

Developing a fitness-related diet may represent part of the solution to being overweight and

physically inactive, but additional goals tend to present additional nuances. Is the goal to be

lean, muscular, strong, or to attain high levels of cardiorespiratory fitness? Each chosen aim

presents a change in the energy composition and nutrient balance needed for success. Addi-

tionally, the targets in many fitness-related programs are associated with caloric expenditure,

but this is the opposite of the goals of sports nutrition. Whereas fitness programs are written

to maximize expended energy, in sports, the emphasis may be placed on sparing energy to make

it through a competition or tolerate a higher training volume. Therefore, the first step in estab-

lishing a nutritional strategy is identifying the diet’s ultimate ambitions.

Factors that Affect Nutrition A variety of factors determine the nutritional make-up of a diet and

influence the timing of nutrient consumption. These can be divided into

primary and secondary factors. Primary factors affect resting and activity

(metabolic) homeostasis. Secondary factors tend to be those associated

with culture, experience, and education.

To identify relevant primary factors, a process of evaluation must occur

in order to detect any health-related issues, such as the presence of genetic

tendency to disease or medical conditions, current deficiencies, and disordered

eating patterns. In addition, the assessment should evaluate anthropometrics,

family history, current behaviors, and activity status. Lastly, the fitness or

performance-related goals need to be evaluated for caloric demands, energy-

system specificity, and recovery needs of the athlete or fitness enthusiast.

Secondary factors include those that affect choices and influence behav-

iors. These tend to be more difficult to measure, as they are rooted in

established habits associated with interpersonal development. Socio economic Culture, experience, and education can all have an impact on nutritional adequacy for health or performance.

DEFINITIONS

Macronutrient –

Nutrients that are consumed in relatively greater quantities to prevent deficiencies and maintain optimal bodily function; includes carbo -hydrates, protein, fat and water.

Micronutrient –

Nutrients that are consumed in relatively small quantities to prevent deficiencies and maintain optimal bodily function; includes vitamins and minerals.

status, where one was raised geographically, who and what a person was exposed to, cultural

and family traditions, and personal efficacy all contribute as dietary influencers. Whereas

primary factors seem to be most relevant, secondary factors should not be disregarded. Rather,

identifying and understanding the influence they present makes it easier to manage them. A

very important concept in sports and fitness nutrition is that food plays a part in the body’s

pleasure system. Therefore, food and drink must be palatable, meet the daily demands of

stress, and also contribute to an acceptable quality of life.

Future Direction of Nutrition Science Individuals respond differently to diets due

to genetic variations that influence how dietary

components are absorbed, metabolized, and

utilized. Nutrigenetics and nutrigenomics

represent emerging areas in nutrition

science and shed light into the interactions

between diets and genetic and genomic varia-

tions. These fields are poised to be essential

tools of sports nutrition, set to improve evi-

dence-based, precise nutritional strategies in

the near future. While these two terms tend to

be used interchangeably, they represent distinct branches of nutrition science. Nutrigenetics

investigates the action of genetic variation, particularly single nucleotide polymorphism (SNP),

on nutrients and diets. Nutrigenomics on the other hand, studies the way nutrients affect

genome-wide expressions, metabolic pathways, and homeostatic control (8). Completion

of the Human Genome Project in 2003 revealed the genetic blueprint of human

beings, marking the turning point for nutrition science and optimization of sports

nutrition, in terms of personalizing and predicting what individual athletes need

to reach peak performance goals. The identification of obesity-associated gene

variants exemplifies this work. People who carry these genes are 22-30%

more likely to be obese than people who do not. Moreover, certain

food/drink choices may exacerbate the obesity risk of individuals carrying

fat-mass and obesity-associated gene markers (9,10); however, healthy lifelong

nutritional strategies and an active lifestyle can significantly attenuate the

obesity risk for the same population (3, 4, 6). Along with the personalized pre-

cision-nutrition concept, the effects of phytochemicals, newly engineered

processed foods, specialized dietary supplements, and diet-microbiota interac-

tions represent some of the hot topics occupying nutrition science.

Precision nutrition integrates the primary factors that compose the person’s current

genotypic/phenotypic status (e.g. anthropometry, RMR, metabolic homeostasis, biochemical

5



Primary factors that impact nutrition:

Geneticsand family

history

Diseaseor medicalconditions

DeficienciesCurrent

dailybehaviors

Activitystatus

Disorderedeating

patterns

Anthropometry Restingmetabolicrate

Metabolichomeostasis

Biochemicalinformation

Medicalconditions

CurrentdeficienciesCaloric

demands

Energysystemsused

Recovery

Demographics

Socioeconomiclevel

Dailybehaviors

PrecisionNutrition

DEFINITIONS

Nutrigenetics –

Study of the interaction between genetics and nutrient intake or dietary practices; seeks to elucidate optimal nutrient intake levels and strategies based on genetic variables.

Nutrigenomics –

Study of the means by which nutrients affect human genetic expressions, metabolic pathways and homeostatic control; seeks to elucidate how differences in dietary intake within ethnical or cultural subgroups have an impact on genetics over time.

Phytochemicals –

Specific active compounds found in plants shown to provide health benefits, but are not essential; not associated with a deficiency when lacking in the diet (e.g., lycopene in tomatoes).

information, medical conditions, current deficiencies, physical activity, caloric demands, energy

systems utilized, recovery) and secondary factors that affect nutrition with reference to general

nutritional guidelines (e.g. demographics, socioeconomic level, culture, food preference,

behavior) in order to provide comprehensive and dynamic nutrition optimization (1, 2).

Nutrition for Sports vs. Fitness All physical activities present a demand above resting homeostasis. Thus,

nutrition for sport must satisfy these energy demands of competition and

training without allowing premature fatigue. But the different aspects

of the activities humans engage in for pleasure and competition present an

assortment of considerations for nutritional support. Most physical activities

are classified as anaerobic or aerobic. From a sports-science perspective, this

concept is somewhat rudimentary, as all metabolism may be sourced during

a practice or competition; however, from a pragmatic perspective, this

model’s simplicity is easier to understand and helps manage nutritional fac-

tors. Anaerobic activities are high-powered, require exertional bursts and

rapid movement velocities, and include tennis, baseball, and hockey. On the

other hand, endurance-based activities are labeled aerobic, such as cross-

country running and triathlon training. Aerobic sports tend to require

sustained lower force outputs for longer durations but are often very

demanding at the competitive level. The nutritional needs of each player or

participant will be specific to the sport’s demands, participation frequency,

and input from all other stressors, including those of psycho-emotional

origin. This scenario suggests that nutritional planning must consider all aspects of being

human, not just the physical ones.

Training programs designed for athletes are based on specific sport analysis. Activities are

selected to align with the desired physiological adaptations and are applied in a planned

sequence by specific dosage. Similarly, the dietary strategy must comply with the athlete’s needs

in a manner specific to the physiological demands of his or her sport. This includes volume and

intensity, which will often vary by season. Identifying the actual demands of

a sport, along with the added challenges of practice and training, is the first

step in developing a nutritional plan for athletic performance.

While similarities exist, eating for fitness differs from eating for per-

formance because the former focuses more on isolated outcomes. Both diet

modes require nutrient specificity to support variations in activity type, inten-

sity, and duration while maintaining desirable levels of body fatness.

Nutrition for fitness emphasizes food intakes that optimize one or more com-

ponents of health-related fitness, often for physique competitions and

single-day events, such as a 10K or adventure race. A diet of this nature must

be well-planned, tends to be more restrictive, and is much more sensitive to

daily variations. On the other hand, athletes need nutrient and caloric density

for performance, so they can be less concerned with calorie counting or even

being visually lean. Athletes never want to run out of energy during a sporting

event, whereas fitness competitors go into contests with low energy provisions

on purpose as the goal is aesthetics. Eating for sports performance also differs

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Nutritional intake for sport must satisfy the energy demands of competition/training and thwart premature fatigue.

Eating for fitness and performance is quite different. Fitness competitors often focus on aesthetics while athletes must make sure they do not run out of energy and can properly recover.

from many fitness goals because of the ideal size and weight specifications associated with each

sport. Whereas fitness nutrition may be employed to add or maintain muscle, athletes may not

have that same desire, as more body weight equates to more work and greater energy demands

during competition.

Regardless of the population, individuals who routinely exert efforts above the adaptation

threshold require more calories than those that do not. Routinely participating in resistance

training and aerobic exercise requires additional levels of both EYN and NEYN beyond that

needed for basic health, and these levels are further increased for sports. The total number

of calories expended each day should be monitored and accounted for to ensure proper

recovery and the presence of suitable glycogen and water in the system for the next bout of

exercise or activity.

Goals of Sports Nutrition Historically, guidelines have suggested consuming a calorie-controlled diet, composed

primarily of a variety of fruits and vegetables, complex carbohydrates, and lean protein, while

limiting the consumption of unhealthy fats, processed carbohydrates, and simple sugars. These

guidelines form the basis of the recommended daily allowances (DRI-RDAs) as presented by

the United States Department of Agriculture and intend to cover the nutrient needs for more

than 90% of the population. And while sound in foundation, these recommendations lack the

specificity to account for those who routinely engage in higher levels of activity. Often,

nutritional adjustments must be made to manage the additional requirements of both EYN

and NEYN. Individuals who participate in fitness training will often burn 1,500 to 2,500

calories a week. Competitive athletes on the other hand, may burn more than 1,000 calories

in a single day.

The first goal depends heavily on carbohydrates to ensure adequate glycogen stores are

preserved in the muscle and liver, and to maintain an appropriate blood-glucose level. Addi-

tionally, healthy fats aid importantly in caloric balance. A key element to this goal is timing

nutrition around physical activity to fuel muscle and liver cells using hormonal advantages.

Fluid and electrolytes are also crucial to facilitate work and recovery demands during and

following activity.

The second goal depends more upon protein and minerals to ensure tissues have specific

nutrients in appropriate quantities to enable repair. Protein and minerals make up soft and hard

tissues and function in the process of catabolism and anabolism in response to external stim-

ulus and the internal environment. While food timing also aids in this goal, precise protein

content and specific nutrient-dense foods rich in calcium, phosphorus, and magnesium should

be included in the diet.

The final goal is rather encompassing, but speaks to the need to treat the body as a complete

organism, so all systems remain efficient. The body uses nutrients for simple to complex tasks

across the metabolic pathways. Amino acids derived from proteins play an important role in

metabolic function and support enzyme and hemoglobin formation. Proteins are further com-

plemented by NEYN, forming structures and serving roles in metabolic and regulatory

operations. This aspect of sports nutrition warrants dietary evaluation for nutrient balance and

sufficiency. Dietary support of the immune system is of key importance to this goal as it is a

primary contributor to recovery.

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To attenuate the stresses associated with training, sports nutrition strives to accomplish three primary goals:

• Providing adequate energy to

support work and recovery.

• Ensuring nutrient balance

supports cellular demands for

growth, maintenance, and repair.

• Providing adequate support for

efficient metabolic and immune

function.

DEFINITIONS

Catabolism –

Metabolic activity associated with the breakdown of tissues or energy reserves within the body.

Anabolism –

Metabolic activity associated with the building of tissues or storage of energy reserves within the body.

The Demands of Sport

8



Table 1. Total Mean Nutritional Intake Among Male Athletes

Energy (Kcal)

Energy (MJ)

CHO (g)

PRO (g)

FAT (g)

Fluid (mL)

Fiber (g) CHO * PRO FAT

2994 ± 556 ★

12.6 ± 2.3 ★

390 ± 76 ★

117 ± 28 ★

96 ± 20 ★

2915 ± 788 ★

34 ± 7 ★

55.1 16.1 ◆

28.8Endurance (n = 157)

3784 ± 593

15.9 ± 2.5

489 ± 76

156 ± 31

119 ± 19

3628 ± 839

45 ± 6 54.8 17.4 27.8Rowing

(n = 34)

2275 ± 211

9.6 ± 0.9

303 ± 32

82 ± 8

76 ± 13

1805 ± 232

23 ± 2 56.0 14.7 29.3Soccer youth

(n = 63)

2700 ± 300

11.4 ± 1.3

361 ± 66

114 ± 13

83 ± 3

2692 ± 464

252 ± 2 55.1 17.3 27.6Soccer talent

(n = 26)

2841 ± 398

11.9 ± 1.7

341 ± 51

135 ± 13

95 ± 14

3550 ± 743

262 ± 5 50.2 19.4 30.4Soccer prof

(n = 30)

3055 ± 542

12.8 ± 2.3

373 ± 86

120 ± 20

104 ± 20

2825 ± 715

265 ± 8 52.5 16.9 30.7Water polo

(n = 12)

2566 ± 138

10.8 ± 0.6

274 ± 25

109 ± 10

105 ± 14

2102 ± 361

218 ± 1 46.0 17.0 37.0Hockey

(n = 7)

3076 ± 638

12.9 ± 2.7

413 ± 84

130 ± 16

92 ± 26

2624 ± 518

36 ± 7 56.2 17.2 26.6Swimming

(n = 11)

2904 ± 481

12.2 ± 2.0

381 ± 77

113 ± 21

98 ± 14

2480 ± 533

31 ± 3 54.2 15.8 30.0Ice skating

(n = 15)

2735 ± 444

11.5 ± 1.9

363 ± 55

111 ± 18

85 ± 18

2389 ± 733

31 ± 6 56.4 16.4 27.1Road cycling

(n = 34)

2946 ± 317

12.4 ± 1.3

419 ± 87

110 ± 11

82 ± 10

3160 ± 735

39 ± 9 59.3 15.4 25.3Running

(n = 8)

2681 ± 239

11.3 ± 1.0

337 ± 35

95 ± 11

90 ± 18

2941 ± 643

29 ± 3 54.6 15.0 30.4

Ultra endurance (n = 55)

2561 ± 395 ★

10.8 ± 1.7 ★

327 ± 56 ★

104 ± 21 ★■

85 ± 14 ★

2455 ± 791 ★

24 ± 4 ★■

53.8 16.5 29.7Team (n = 138)

3212 ± 225

13.5 ± 0.9

400 ± 21

150 ± 29

99 ± 9

2759 ± 398

32 ± 1 52.2 19.0 28.8Track cycling

(n = 5)

2739 ± 696

11.5 ± 2.9

383 ± 85

109 ± 27

76 ± 38

2599 ± 783

35 ± 10 59.4 16.0 24.6BMX

(n = 12)

2969 ± 127

12.5 ± 0.5

369 ± 15

132 ± 3

99 ± 12

3352 ± 110

35 ± 2 52.5 17.6 29.9Sprint/bobsled

(n = 4)

3308 ± 172

13.9 ± 0.7

300 ± 53

161 ± 12

144 ± 17

3314 ± 290

29 ± 5 40.6 19.8 39.6CrossFit

(n = 5)

2291 ± 288

9.6 ± 1.2

263 ± 59

111 ± 17

81 ± 3

2519 ± 556

25 ± 7 47.7 19.7 32.6Archery

(n = 6)

2846 ± 395

12.0 ± 1.7

348 ± 61

127 ± 24 ■

94 ± 28

2815 ± 475

32 ± 6 ■ 52.3 18.0

◆29.8Strength

(n = 32)

Absolute Mean Intake

Macronutrient Contribution for Total Energy (TE%)

Intake values are expressed as mean intake ± SD; Differences between categories are indicated by symbols (one-way ANOVA: p < 0.05, with post-hoc Bonferroni correction), each comparison between groups has its own symbol; ★ Endurance vs. Team, ◆ Endurance vs. Strength and ■ Team vs. Strength; No analysis was performed for testing differences between sports within the categories for endurance, team, and strength sports; * TE% for CHO includes estimated TE% of dietary fiber.

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Table 2. Total Mean Nutritional Intake Among Female Athletes

Energy (Kcal)

Energy (MJ)

CHO (g)

PRO (g)

FAT (g)

Fluid (mL)

Fiber (g) CHO * PRO FAT

2459 ± 520 ★◆

10.3 ± 2.2 ★◆

312 ± 58 ★◆

97 ± 19 ★

81 ± 28 ★

2842 ± 930 ★

32 ± 8 ★◆

54.2 16.4 ★◆

29.5Endurance (n = 83)

2909 ± 662

12.2 ± 2.8

362 ± 50

112 ± 23

99 ± 45

3228 ± 657

39 ± 10 54.2 16.1 29.7Rowing

(n = 26)

1965 ± 293

8.3 ± 1.2

256 ± 31

76 ± 4

66 ± 13

1695 ± 255

20 ± 5 54.2 15.8 30.0Soccer youth

(n = 16)

1998 ± 86

8.4 ± 0.4

260 ± 12

87 ± 5

59 ± 9

2585 ± 485

27 ± 3 55.6 17.8 26.6Volleyball

(n = 18)

1873 ± 111

7.9 ± 0.5

245 ± 29

75 ± 7

58 ± 12

2087 ± 389

24 ± 7 55.6 16.4 28.0Water polo

(n = 12)

2056 ± 207

8.6 ± 0.9

244 ± 44

93 ± 0

71 ± 10

2794 ± 594

23 ± 3 49.9 18.5 31.6Rugby Sevens

(n = 29)

2091 ± 373

8.8 ± 1.6

259 ± 37

89 ± 10

70 ± 20

2216 ± 562

26 ± 3 52.9 17.5 29.6Hockey

(n = 11)

1955 ± 224

8.2 ± 1.0

222 ± 21

92 ± 27

69 ± 3

2767 ± 617

24 ± 8 48.0 19.4 32.6Handball

(n = 18)

2495 ± 335

10.5 ± 1.4

341 ± 41

105 ± 13

70 ± 7

2429 ± 652

32 ± 3 56.8 17.2 26.0Swimming

(n = 9)

2224 ± 424

9.3 ± 1.8

283 ± 61

85 ± 11

78 ± 12

2209 ± 468

26 ± 3 53.2 15.8 31.0Ice skating

(n = 11)

2127 ± 363

8.9 ± 1.5

264 ± 53

92 ± 14

69 ± 13

3121 ± 1324

30 ± 9 53.1 17.9 29.0Road cycling

(n = 14)

2299 ± 102

9.7 ± 0.4

297 ± 25

96 ± 5

73 ± 10

2429 ± 977

30 ± 6 53.7 17.3 29.0Running

(n = 11)

2205 ± 288

9.3 ± 1.2

280 ± 61

76 ± 15

75 ± 12

2949 ± 1080

29 ± 8 54.6 14.3 31.1

Ultra endurance (n = 12)

1997 ± 201 ★

8.4 ± 0.9 ★

247 ± 32 ★

87 ± 10 ★

66 ± 11 ★

2441 ± 631 ★

24 ± 5 ★

52.2 17.8 ★

30.0Team (n = 104)

2202 ± 46

9.3 ± 0.2

285 ± 13

97 ± 18

67 ± 2

2385 ± 885

26 ± 4 54.0 17.9 28.1Track cycling/BMX

(n = 6)

2269 ± 401

9.5 ± 1.7

297 ± 58

88 ± 16

75 ± 19

2514 ± 778

24 ± 6 54.4 16.4 29.2Sprint/bobsled

(n = 8)

2609 ± 329

10.9 ± 1.4

240 ± 27

130 ± 37

108 ± 26

2834 ± 645

33 ± 9 41.2 20.3 38.5CrossFit

(n = 6)

2244 ± 296

9.4 ± 1.2

278 ± 58

101 ± 7

72 ± 5

3670 ± 788

30 ± 2 53.1 18.5 28.4Sailing

(n = 6)

1566 ± 92

6.6 ± 0.4

199 ± 29

72 ± 8

48 ± 6

1691 ± 136

20 ± 1 53.6 18.9 27.5Gymnastics

(n = 13)

2073 ± 417 ◆

8.7 ± 1.7 ◆

251 ± 46 ◆

92 ± 23

69 ± 21

2447 ± 866

25 ± 6 ◆ 51.8 18.4

◆29.8Strength

(n = 39)

Absolute Mean Intake

Macronutrient Contribution for Total Energy (TE%)

Intake values are expressed as mean intake ± SD. Differences between categories are indicated by symbols (one-way ANOVA: p < 0.05, with post-hoc Bonferroni correction), each comparison between groups has its own symbol, ★ Endurance vs. Team, ◆ Endurance vs. Strength and ■ Team vs. Strength. No analysis was performed for testing differences between sports within the categories for endurance, team, and strength sports * TE% for CHO includes estimated TE% of dietary fiber (13).

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Table 3. Energy Intake of Endurance Athletes in the Preparation and Competition Phases (5)

Preparation Competition

Endurance discipline n Energy intake [kcal/day] Energy intake [kcal/kg.day] n Energy intake [kcal/day] Energy intake [kcal/kg.day] Cyclists Total 46 3789 ± 765d,e,f 52.3 ± 13.3d,e 133 3600 ± 1102d 46.9 ± 17.7d,f Male 46 3789 ± 764d,e 52.3 ± 13.3d,e 125 3603 ± 1137 45.9 ± 18.0 Female – – – – – – Runners Total 278 2489 ±425a 38.2 ± 7.8a 272 3042 ±788 42.7 ± 4.7 Male 207 2640 ± 366a,b,f 38.3 ± 8.6a 203 3298 ± 713b 43.8 ± 3.2b Female 71 2046 ± 230a 38.0 ± 4.6c 69 2291 ± 443 39.4 ± 6.4 Swimmers Total 73 3366 ± 902a,d,e,g 48.7 ± 9.6a,d,e 55 2769 ± 681g,h 40.1 ± 7.7g Male 39 3963 ± 762a,b 53.2 ± 9.5a,b,d,e 24 3462 ± 341b 46.2 ± 6.5b Female 34 2683 ± 450a,d,e 43.6 ± 6.9a,e 31 2234 ± 256 35.4 ± 4.7 Rowers Total 70 2426 ± 448a 33.9 ± 4.5a 15 3633 ± 1097 46.8 ± 10.9 Male 24 2921 ± 326b,f 36.0 ± 0.1b – – – Female 46 2168 ± 330 32.8 ± 5.2c – – – Cross-country skiers Total 138 3224 ± 917a,d,e,g 48.3 ± 12.7a,d,e 33 2091 ± 53.2d,e,f,g 32.7 ± 2.9c Male 124 3287 ± 876d,f,g 48.3 ± 11.6d,e – – – Female 14 2663 ± 1107d,e 49.1 ± 20.3 – – – Triathletes Total 16 3162 ± 159d,e 45.7 ± 2.6e – – – Male 16 3162 ± 159d,e 45.7 ± 2.6e – – – Female – – – – – – Other endurance athletes Total 96 3261 ± 282a,d,e,g 46.5 ± 5.1a,d,e 14 4656 ± 1070 – Male 90 3274 ± 286a,d,f,g 46.3 ± 5.2a,d,e,f 14 4656 ± 1070c,d,f,g,h – Female – – – – – – Total Total 717 2915 ± 761a 42.8 ± 10.5 531 3156 ± 967 43.5 ± 11.3 Male 546 3111 ± 717a,b 44.0 ± 10.6b 407 3405 ± 940b 44.8 ± 11.9b Female 171 2291 ± 525 39.0 ± 9.1 124 2337 ± 483 39.3 ± 7.9 Note. Data are shown in weighted mean and standard deviation of the weighted mean (Xw ± SDw) n = cumulative number of subjects, – = insufficient data a Significantly different from athletes of the same endurance discipline and sex during competition phase (p<0.01) b Significantly different from females of the same endurance discipline and seasonal training phase (p<0.01) c Significantly different from all other endurance disciplines of the same sex and seasonal training phase (p<0.05) d Significantly different to runners of the same sex and seasonal training phase (p<0.05) e Significantly different to rowers of the same sex and seasonal training phase (p<0.05) f Significantly different to swimmers of the same sex and seasonal training phase (p<0.05) g Significantly different to cyclists of the same sex and seasonal training phase (p<0.05) h Significantly different to cross-country skiers of the same sex and seasonal training phase (p<0.05)

Specialized nutrition for sports or taxing physical activity implies that

athletes and fitness competitors must consume a diet that supports the meta-

bolic demands of training and competition while accounting for recovery.

Individual sports have been evaluated for specific nutritional require-

ments, and not surprisingly, research suggests that energy is the primary

predictor of success. Energy produces force, transfers and breaks down

nutrients, buffers nutrient byproducts, and regulates temperature. Not sur-

prisingly, the demand’s magnitude depends on the movement’s intensity and

duration.

Nutritional needs can be categorized by comparing different sports and

fitness activities. While no single diet is appropriate for all sports, nutrient

commonalities exist that can be categorically applied for appropriate recom-

mendations. Essentially, certain activities align nutritionally due to energy

system specificity and the similar caloric expenditure required at the compet-

itive level.

Historically, it has been thought that endurance athletes need more carbohydrates and

strength athletes more protein, but this is not necessarily accurate. Since endurance athletes

have a higher energy intake, they consume higher quantities of all nutrients, inclusive of carbo-

hydrates and protein. While protein is important for recovery, the idea that strength athletes

consume more protein than other athletes has not been confirmed. In fact, across a sample of

endurance, team, and strength-based sport athletes, consumption of energy-yielding nutrients

has a high level of consistency when expressed as percentage of the diet. That said, the current

consensus on carbohydrate and protein intake suggests that, while predictive, it is better not to

specify nutrient intake as a percentage of the total dietary energy intake. Rather, the need by

grams per kilogram of body weight (g·kg−1) should be determined to ensure relative require-

ments are being met. Part of the reason intake must be expressed in this manner is that the

current recommendations for energy intake demonstrate a considerable degree of variation.

The recommended intake range for carbohydrates and protein is rather broad, 3 to 12 g·kg−1 per

day for CHO and 1.2 to 2.0 g·kg−1 per day for protein, respectively. When expressed as a per-

centage, the information becomes specific to the quantity of calories and may or may not

address the needs of the body when adjusted for weight.

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Research suggests the primary nutritional predictor for success in sport is energy. Energy is needed to produce force, transfer and break down nutrients, buffer nutrient byproducts, and regulate temperature.

Consider the following for a 70 kg male athlete: 70 kg x 1.5 g/kg = 105 g of protein per day = 420 kcal

15% of 2,400 kcal diet = 360 kcal

If this individual followed the RDA for protein, he would not meet his daily need of 1.5

g/kg/day. Individually breaking energy nutrients down by grams per weight and assigning

desirable endocrine-timing relationships should be of primary consideration for athletes and

physique competitors.

Additionally, these recommendations have a historical foundation, which may not be as

accurate today given the advancing understanding of training methods for high-level athletes.

Endurance and team-sports athletes for instance, also perform intense weight training. So, the

question now exists as to whether the significant differentiation in dietary intake between sport

disciplines is as appropriate as once thought given the multiple, overlapping stress demands.

Consider tables 1-3.

Each sport’s nuances provide the opportunity for fine-tuning via adjustments in energy-

nutrient recommendations, particularly for specific training and performance needs at different

times of the year. Additionally, males and females will demonstrate differences in nutritional

need particularly in total calories and specific micronutrients. That said, these differences are

not overly pronounced. When all sport athletes were compared, the mean estimated energy

intake, including nutritional supplements, for males was between 2,561 and 2,994 kcal per day,

whereas the mean energy intake for females ranged from 1,997 and 2,457 kcal per day. Not sur-

prisingly, the highest average intakes for males and females across all nutrients manifested in

the endurance sports categories. On the other hand, consider a systematic review of 48 studies

that analyzed the energy intake fluctuations of 717 highly trained endurance athletes across a

training season: it was found that relative energy intake during competition phases did not differ

from the preparation phase among either male or female endurance athletes (Table 3); however,

endurance athletes’ energy expenditure remained significantly higher than energy intake in both

preparation and competition phases (5). The same table also reflects the significant variations

in athletes’ energy consumption across different disciplines, even if all the events are classified

as endurance sports.

When dietary assessments are performed, most athletes seem to meet the requirements for

protein, based on minimum recommendations of 1.2 g·kg−1 but fail to ingest carbo hydrates at

the recommended level. This suggests one of two things: either the current recommendations

for carbohydrates are too high, or most athletes could benefit from additional carbohydrates in

their diet. The obvious premise behind elevated carbohydrate consumption is that sport-based

activities are performed at intensities that cannot be supported by the aerobic metabolism of

fats and proteins. This means carbohydrates serve as the primary fuel for energy metabolism

in sports. Even “aerobic” activities like distance running, cycling, and long-distance swimming

all use carbohydrates to fuel the faster speeds used at the competitive level. The need for protein

is well justified, but most dietary recommendations aimed at athletic performance attempt to

reach a proportion of 55-70% carbohydrates and 25-35% fat with protein only supplying

between 10-15% of calories. Interestingly, when successful athletes are analyzed, they all con-

sume more than 15% protein, with the exception of female ultra-endurance athletes. When

categorical activities are analyzed (e.g., endurance, team sports, strength) no group exceeds 60%

of calories from carbo hydrates. Certainly, endurance athletes consume the most carbohydrates,

but even their diets are at the bottom of the recommended range with a mean of 55%.

These findings seem to be consistent with non-elite athletes of varied endurance sports,

inclusive of winter triathlon (e.g., snowshoeing, skating, and cross-country skiing), winter pen-

tathlon (e.g., winter triathlon sports, cycling, and running), Ironman (IM: swimming, cycling,

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running), and half-distance Ironman (IM 70.3). Nutritional analysis of these athletes identified

only 45.7% of all athletes reported consuming the recommended intake for carbohydrates, with

the highest proportion (66.7%) being those who competed in the half-ironman event. Equally

consistent with the elite athletes, the vast majority, (87.1%) reported consuming at least 1.2 g·kg-

1·day−1 of protein, and the majority of those who demonstrated sufficiency reported consuming

more than 1.6 g·kg−1·day−1. There was no difference in the proportion of athletes achieving the

recommended carbohydrate and protein intakes between men and women. These findings sug-

gest that among athletic populations, most do not meet the current recommendations for

carbohydrates, and many report total caloric intakes below more favorable estimates.

Energy though, is not the only limiting factor in human performance.

Athletes must not only fuel properly but should engage in training, practice, and

competition in a well-hydrated state to limit water and electrolyte deficits.

When an athlete is not properly hydrated, he or she loses extracellular fluid

stores and experiences shifts in electrolyte balance. This causes further detri-

ment to cellular function and a fairly linear decline in performance. To prevent

this problem, athletes must consume adequate energy in the form of carbo -

hydrates and manage fluid intake before, during, and after activity. Available

evidence suggests that many athletes enter physical activity with non-optimal

hydration levels and some experience some degree of dehydration even before

they start activity. Additionally, during training and practice, many fail to

drink enough to match sweat losses, whereas others drink too much, risking

hyponatremia. Athletes must learn a personalized hydration strategy balanced

with micronutrient intake that meets the needs of exercise, environmental

factors, and specific individual differences, as well as competition regulations.

Whereas nutrition before and during an event is relevant, recovery from activity requires

the most attention. Restoring liver and muscle glycogen stores is extremely important because

the metabolic opportunity to maximize stores has a limited window. Basic recommendations

have included consumption of up to 1.2 g⋅kg−1⋅h−1 of carbohydrate and 40 g of protein to aug-

ment protein synthesis. Consumption of appropriate nutrient sources should be prioritized

within 20-30 min following activity. Additionally, fluid and micronutrient needs should be

addressed within this time frame as well. A common recommendation is that 150% of body mass

lost during exercise should be consumed within 1 hour, with matched electrolytes. This measure

readies the body for recovery and for future muscle-tissue activity. An under-fueled and dehy-

drated athlete cannot compete optimally and experiences a much higher risk for injury. The

following text will review peak performance strategies across a broad range of activities.

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Athletes are not only supposed to be properly fueled, but also need to engage training, practice, and competition in a well-hydrated state to limit water and electrolyte deficits.

DEFINITIONS

Hyponatremia –

A dangerous condition associated with abnormally low sodium levels in the blood (<135 mmol/L).

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REFERENCES:

Introduction to Sport Nutrition

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