14 Body Composition and Nutrition for Sport chapter
Slide 2
Body Build, Size, and Composition Body build is the form or
structure of the body. Muscularity Linearity Fatness Body size is
determined by height and weight. Body composition refers to the
chemical composition of the body Fat mass Fat-free mass
Slide 3
Three Models of Body Composition Adapted, by permission, from
J.H. Wilmore, 1992, Body weight and body composition. In Fasting,
body weight, and performance in athletes: Disorders of modern
society, edited by R. Brownell and J.H. Wilmore (Baltimore, MD:
Lippincott, Williams, and Wilkins), 77-93.
Slide 4
Did You Know... ? Fat-free mass is composed of all of the bodys
nonfat tissue, including bone, muscle, organs, and connective
tissue. Lean body mass includes all fat- free mass along with
essential fat. Lean body mass is difficult to measure, so the fat
mass/fat-free mass model is most often used.
Slide 5
Did You Know... ? Body composition is a better indicator of
fitness than body size and weight. Being overfat (not necessarily
overweight) has a negative impact on athletic performance. Standard
heightweight tables do not provide accurate estimates of what an
athlete should weigh because they do not take into account the
composition of the weight. An athlete can be overweight according
to those tables yet have very little body fat.
Densitometry Body density = Body mass Body volume Body mass =
measured on a regular scale Body volume = measured using
hydrostatic (underwater) weighing accounting for water density and
air trapped in the lungs % body fat = (495 body density) 450
Slide 8
Underwater Weighing Technique to Determine Density of the Body
Tom Pantages
Slide 9
UNDERWATER WEIGHING TECHNIQUE
Slide 10
Dual-Energy X-Ray Absorptiometry Machine Photo courtesy of
Hologic, Inc.
Slide 11
Bod Pod device Photo courtesy of Life Measurement, Inc.
Slide 12
Measuring Skinfold Fat Thickness at the Triceps Skinfold Site
Human Kinetics
Slide 13
Bioelectric Impedance Technique for Assessing Relative Body Fat
Human Kinetics
Slide 14
Did You Know... ? Inaccuracies in densitometry are due to the
variation in the density of the fat-free mass from one individual
to another. Age, sex, and race affect the density of fat- free
mass.
Slide 15
Body Composition and Performance Maximizing Fat-Free Mass
Desirable for strength, power, and muscular endurance Undesirable
for endurance or jumping sports if the result is weight gain
Minimizing Relative Body Fat Desirable, especially in sports in
which the body weight is moved through space Improves speed,
endurance, balance, agility, and jumping ability
Slide 16
Relative Body Fat in Elite Female Track and Field Athletes Data
from J.H. Wilmore et al., 1977, Body physique and composition of
the female distance runner, Annals of the New York Academy of
Sciences 301: 764-776.
Slide 17
Risks With Severe Weight Loss Dehydration Chronic fatigue
Disordered eating and eating disorders Menstrual dysfunction Bone
mineral disorders
Slide 18
COMPOSITION OF WEIGHT LOSS
Slide 19
Appropriate Weight Guidelines Maximize performance within the
specific sport (See table 14.1, page 327) Are based on body
composition Emphasize relative body fat rather than total body mass
Use a range of relative fat values that are considered acceptable
for the athletes age and sex
Slide 20
Achieving Optimal Weight Combine proper diet with exercise.
Lose no more than 1.0 kg (2 lb) per week. Reduce caloric intake to
200 to 500 kcal less than daily energy expenditure. Use moderate
resistance and endurance training.
Slide 21
Six Nutrient Classes Carbohydrate Fat Protein Vitamins Minerals
Water
Slide 22
Recommended Balance of Nutrients 55% to 60% carbohydrate Less
than 30% fat (less than 10% saturated) 10% to 15% protein
Slide 23
Carbohydrate (CHO) Provides energy, particularly during
high-intensity exercise Regulates fat and protein metabolism
Exclusive energy source for the nervous system Synthesized into
muscle and liver glycogen Sources include grains, fruit,
vegetables, milk, and sweets Glycemic index influences performance
and health
Slide 24
Influence of Dietary Carbohydrate (CHO) on Muscle Glycogen
Stores During Repeated Days of Training D.L. Costill and J.M.
Miller, "Nutrition for endurance sport: Carbohydrate and fluid
balance," 1980, International Journal of Sports Medicine 1: 2-14.
Reprinted by permission.
Slide 25
Relationship Between Preexercise Muscle Glycogen Content and
Exercise Time to Exhaustion D.L. Costill and J.M. Miller,
"Nutrition for endurance sport: Carbohydrate and fluid balance,"
1980, International Journal of Sports Medicine 1: 2-14. Reprinted
by permission.
Slide 26
CHO Types Simple Sugar Elevates blood glucose levels Relies on
insulin to move it to cells When intake exceeds usage, stored
within the cells as fat Complex CHO Requires more time to break
down Produces a smaller and slower rise in blood glucose Has less
impact on blood lipid levels
Slide 27
Key Points Ergogenic Properties of CHO Muscle glycogen loading
may delay onset of fatigue. Maintaining normal blood glucose levels
may allow the muscles to obtain more energy from blood glucose,
sparing liver and muscle glycogen reserves. Activities over 1 hour
can be enhanced when carbohydrate is consumed within 5 minutes of,
over 2 hours before, and at frequent intervals during the
activity.
Slide 28
Influence of Exercise Intensity (%VO2) on Muscle Glycogen
Stores Adapted, by permission, from A. Jeukendrup and M. Gleeson,
2004, Sport nutrition: An introduction to energy production and
performance (Champaign, IL: Human Kinetics). Original data from
Gollnick, Piehl, and Saltin.
Slide 29
CHO INTAKE AND PERFORMANCE
Slide 30
Effects of Preexercise Carbohydrate Feeding on Blood Glucose
Levels During Exercise Adapted, by permission, from D.L. Costill et
al., 1977, "Effects of elevated plasma FFA and insulin on muscle
glycogen usage during exercise," Journal of Applied Physiology
43(4): 695-699.
Slide 31
Replenishment of Muscle Glycogen Stores Using Two Different
Regimens of Carbohydrate Replacement Adapted, by permission, from
J.L. Ivy et al., 1988, "Muscle glycogen synthesis after exercise:
Effect of time of carbohydrate ingestion," Journal of Applied
Physiology 64: 1480-1485.
Slide 32
Did You Know... ? Carbohydrate intake during exercise does not
produce the same hypoglycemic effects as preexercise intake. This
difference may be caused by increased muscle fiber permeability
that decreases the need for insulin during exercise, or
insulin-binding sites may be altered during muscular activity.
Slide 33
Fat Makes up cell membranes and nerve fibers Provides up to 70%
energy at rest Cushions vital organs Produces all steroid hormones
Transports and stores fat-soluble vitamins Preserves body heat
Slide 34
Key Points Ergogenic Properties of Fat Use of FFAs for energy
production can delay exhaustion. Chronic endurance training results
in more reliance on fat for energy. For some individuals, caffeine
promotes fat use and improves performance.
Slide 35
Protein Makes up cell structure Provides up to 10% energy
during exercise Produces hemoglobin, enzymes, and many hormones
Maintains normal blood osmotic pressure Forms antibodies Can be
energy source Breaks down into amino acids to be used by the
body
Slide 36
Key Points Ergogenic Properties of Protein Builds fat-free
muscle mass. Strength athletes need 1.4 to 1.8 g per kg body
weight. Endurance athletes need 1.2 to 1.4 g per kg body weight.
Diets exceeding 2.0 g per kg body weight per day have not been
proven to provide additional benefits and may damage kidney
function.
Slide 37
Vitamins Fat Soluble A, D, E, and K Absorbed from digestive
tract and bound to lipids Excessive intake can cause toxic
accumulations Water Soluble B-complex and C Absorbed from digestive
tract with water Excess is excreted
Slide 38
B-Complex Vitamins Include more than 1 dozen vitamins Involved
in energy production If deficiency, supplementation may facilitate
performance
Slide 39
Vitamin C Formulates and maintains collagen in connective
tissue Helps metabolize amino acids Helps synthesize epinephrine,
norepinephrine, and corticoids Promotes iron absorption May help
fight infection and function as antioxidant Supplementation does
not appear to improve performance if no deficiency exists
Slide 40
Vitamin E Stored in muscle and fat Prevents oxidation of
vitamins A and C Acts as antioxidant to disarm free radicals May
decrease risk of coronary artery disease Supplementation has not
been proven to improve performance
Slide 41
Minerals Electrolytes are mineral compounds that can dissociate
into ions in the body. Macrominerals are minerals that your body
needs 100 g of per day. Microminerals are minerals that your body
needs less than 100 g of per day.
Slide 42
Calcium Most abundant mineral in the body Stored in the bones
Facilitates bone growth and maintenance Essential in nerve impulse
transmission Activates enzymes and regulates cell membrane
permeability Essential for normal muscle function
Slide 43
Phosphorus Commonly linked to calcium in form of calcium
phosphate Provides strength and rigidity to bones Essential to
metabolism and component of ATP Part of cell membrane structure
Helps maintain constant blood pH
Slide 44
Iron Helps form hemoglobin and myoglobin Deficiency is
relatively common, more so in women If deficiency, supplementation
can improve aerobic capacity
Slide 45
Sodium, Potassium, and Chloride Separate electrical charge
across neuron and muscle cell membranes Maintain bodys water
balance and distribution Maintain normal osmotic equilibrium and pH
Maintain normal cardiac rhythm
Slide 46
Did You Know... ? Vitamins and minerals do not appear to have
any ergogenic value in amounts beyond the RDA. Taking them in
amounts greater than RDA will not improve performance and may be
dangerous.
Slide 47
Water Makes up blood plasma, which transports and delivers
nutrients to tissues Makes up body fluids that regulate pH
Dissipates excess body heat during exercise Maintains blood
pressure
Slide 48
BODY WATER AT REST
Slide 49
Key Points Water Balance During Exercise Metabolic water
production increases as body heat increases. Water loss increases
during exercise due to sweating. Blood flow to the kidneys
decreases to prevent dehydration. If dehydration exceeds 2% body
weight, physical performance is impaired.
Slide 50
Decline in Running Velocity With Dehydration of About 2% of
Body Weight Reprinted, by permission, from L.E. Armstrong, D.L.
Costill, and W.J. Fink, 1985, "Influence of diuretic- induced
dehydration on competitive running performance," Medicine and
Science in Sports and Exercise 17: 456-461.
Slide 51
Key Points Electrolyte Balance During Exercise Loss of water
via sweating disrupts electrolyte balance. Sodium and chloride are
the most abundant electrolytes in sweat. Excess electrolytes are
excreted in the urine during rest, but less so during exercise.
Dehydration causes aldosterone to promote renal retention of sodium
and chloride ions, raising their concentrations in the blood. This,
in turn, triggers thirst.
Slide 52
Effects of 6 h of Treadmill Running in the Heat on Heart Rate
Data from S.I. Barr, D.L. Costill, and W.J. Fink, 1991, "Fluid
replacement during prolonged exercise: Effects of water, saline or
no fluid," Medicine and Science in Sports and Exercise 23:
811-817.
Slide 53
Key Points Replacing Fluid Losses The need to replace body
fluids is greater than the need to replace electrolytes. The thirst
mechanism does not match the hydration state, so it is best to
consume more fluid than thirst dictates. Water intake during
prolonged exercise reduces the risk of dehydration and optimizes
performance. Drinking too much fluid can result in hyponatremia
(low levels of plasma sodium), which can cause confusion,
disorientation, and seizures. (continued)
Slide 54
Key Points (continued) The Athletes Diet There is no one
typical diet of an athlete; but it is important that athletes and
active people alike meet their RDA of nutrients. Athletes can get
the nutrition they need with a strictly vegetarian diet as long as
the foods they select include a balance of essential nutrients and
calories. The precompetition meal can ensure a normal blood glucose
level and prevent hunger; it should include 200 to 500 kcal of
foods that are easily digestible and are eaten no less than 2 hours
before competition.
Slide 55
strands Glycogen Loading 1.Complete an exhaustive training bout
7 days before event. 2.Eat fat and protein for next 3 days and
reduce training load; this increases glycogen synthesis. 3.Eat a
carbohydrate-rich diet for remaining 3 days before event and reduce
training load; because of increased glycogen synthesis, more
glycogen is stored.
Slide 56
Shermans Glycogen Loading 7 Days Before Competition Reduce
training intensity. Eat a normal, healthy mixed diet with 55%
carbohydrate. 3 Days Before Competition Reduce training to daily
warm-up of 10 to 15 minutes. Eat a carbohydrate-rich diet.
Slide 57
Two Regimens for Muscle Glycogen Loading Data from P.-O.
Astrand, 1979, Nutrition and physical performance. In Nutrition and
the world food problem, edited by M. Rechcigl et al. (Basel,
Switzerland: S. Karger).
Slide 58
Muscle Glycogen Resynthesis
Slide 59
Effects of Solution Characteristics on the Rate of Gastric
Emptying Volume of the solutionIncreases with larger volumes
Caloric contentDecreases as the caloric density increases
OsmolarityDecreases with hyperosmolar solutions TemperatureFaster
for cooler fluids than warm solutions pHDecreases with more acidic
solutions Solution characteristicRate of emptying
Slide 60
Gastric Emptying Slows at exercise intensities above 70% VO
2max Is the same rate at rest as it is at exercise intensities
below 70% VO 2max Affected by an individuals fitnessthe more fit,
the less exercise affects it Not affected by exercise duration
Affected differently by different types of activities..
Slide 61
CHO AND RATE OF GASTRIC EMPTYING
Slide 62
Key Points Designing Sport Drinks Fructose, glucose, and
maltodextrin may empty fastest from digestive tract. Concentrations
less than 11 g of CHO per 100 ml empty faster but dont supply the
full energy needed for prolonged exercise. Athletes prefer a drink
with a light flavor and no strong aftertaste. During prolonged
exercise, water intake is primary, but drinking 4 g to 8 g of CHO
per 100 ml solution every 10 to 15 minutes reduces dehydration and
provides a partial energy supplement.