“Aside from the limits imposed by heredity and the physical improvements associated with training, no factor plays a bigger role in exercise performance than does nutrition.”
Dr. David Costill, 1988
Energy Balance
Hypothetical daily energy needs of an Ironman triathlete in training.
Activity METS Duration (h)
Energy Expenditure (kcal)
Sleep 0.9 8.0 540
Office work 1.5 8.0 900
Running (7.5 mph)* 13.5 0.8* 810
Swimming (2 mph)* 8.0 0.5* 318
Bicycling (18.6 mph)* 12.0 1.7* 1,530
Home activities (e.g. cooking, washing dishes, etc.)
2.5 3.0 563
Miscellaneous activities (reading newspaper, talking on phone, etc.)
1.3 2.0 195
4,856
*Based on data from O’Toole, 1989. Energy expenditure calculated as: (METS 75 kg body weight hours of activity = kcal)
Daily Energy Intakes of Elite AthletesSport Energy Intake (kcal/d) Reference
Tour de France 5,972 Van Erp-Baart, 1989
Triathlon 4,778 Van Erp-Baart, 1989
Cycling 4,300 Van Erp-Baart, 1989
Swimming 4,018 Grandjean, 1989
Football (U.S.) 3,826 Grandjean, 1989
Soccer 3,583 Van Erp-Baart, 1989
Body Building 3,344 Van Erp-Baart, 1989
Running 3,105 Van Erp-Baart, 1989
U.S. Males (19-34) 2,667 Grandjean, 1989
Map of the Trek
Torry Larsen Rune Gjeldnes
WR 2,928 km Unsupported Ski Trek March - June, 1996
WR 2,928 km Ski Trek
Details
• 2,928 km (1,815 miles) in 83 days• 9 hrs/d of trekking (~22 miles/d)• Each pulling 150 kg (330 lb sled)• Average energy intake was 6,000 kcal/d• Average weight loss was only 5.3 kg (~12 lbs) and
4% reduction in body fat (DEXA)• Average weight loss of Army Rangers during 64
days of training is 10 – 20 kg (22 – 44 lbs)!
Macronutrients
60 -70% of kcal350-600g/d5-10g/kg/d
CHOPRO
FAT
15-25% of kcal
15% of kcal1.2-1.8g/kg/d
Macronutrient Composition and Performance:Overview
Dietary Protein
0.3 0.5 0.7 0.9 1.1 1.3 1.5 Protein Intake (g/kg/d)
80
60
40
20
0
-20
-40
-60
-80
Nitr
oge
n B
ala
nce
(m
g/k
g/d
)
RDA
Meredith et al., 1989
Mean = .94g/kg/d
300
250
200
150
100
50
Wh
ole
Bo
dy
Pro
tein
Syn
thes
is (
mg/
kg/h
r)
0.9 1.4 2.4 Protein Intake (g/kg/d)
Sedentary
Strength Athletes
Tarnopolsky et al., 1992
* *
Current Protein Intake Recommendations
Adult RDA (1989) 0.8g/kg/d
ADA/CDA Recommendations for Active People(1993)
1.0-1.5g/kg/d
Foods, Nutrition, and Sports PerformanceInternational Scientific Consensus (1992) Strength Athletes Endurance Athletes
1.2-1.8g/kg/d1.2-1.4g/kg/d
Current U.S. Intake Data, NHANES II (1991) ~1.6g/kg/d
Nationwide Survey on Nutritional Habits of EliteAthletes (van Erp-Baart et al., 1989) Strength Athletes Endurance Athletes
1.4-2.5g/kg/d1.3-3.0g/kg/d
Protein and Amino Acid Contents of Common Foods and Popular
Supplements
Food or Supplement Amount Equal to 24g Protein Price/serving
Skim Milk 3 cups (24 fl oz) $0.55
Liquid Gainer’s Fuel 1 bottle (also ~ 24 fl oz) $2.79
Dry milk powder 1 cup $0.17
Gainer’s Fuel powder 3 scoops $0.86
Amount Equal to 7g AA’s
Chicken breast 1 oz $0.10
Amino Fuel AA’s 13 tablets $1.62
Dietary Carbohydrate
Why Are Carbohydrates So Important?
Carbohydrates are the primary muscular fuel source for intense exercise
0
10
20
30
40
50
60
Rest 20% 40% 60% 80% 100%
AEROBIC POWER
FA
T (
%)
40
50
60
70
80
90
100
CH
O (%
)FAT
CHO
Adapted from: Brooks and Mercier, 1994The “Crossover Concept”
0
50
100
150
200
250
300
350
25 65 85
% VO2max
kca
l/k
g/m
inMuscle Glycogen
Muscle Triglycerides
Plasma FFA
Plasma Glucose
Adapted from: Romijn et al., 1993
Why Are Carbohydrates So Important?
Carbohydrates are the primary muscular fuel source for intense exercise
Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue
0
0.5
1
1.5
0 15 30 45 60
Work Time (min)
Mus
cle
G ly
coge
n(g
/100
g w
et m
uscl
e)
Adapted from: Bergstrom and Hultman, 1967
0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 90 100 110 120
Time (min)
Mus
cle
Gly
coge
n (m
mol
/kg
ww
)
150% VO2max
120% VO2max83% VO2max 64% VO2max
Adapted from: Gollnick, 1974
Adapted from: Bergstrom et al., 1967
0
1
2
3
4
5
0 50 100 150 200 250 300
Time to Exhaustion (m in) at 75% VO2max
In it
ial M
uscl
e G
lyco
gen
(g/1
00g
m u
scle
)
r = 0.92
Low CHO Diet Normal Diet High CHO Diet
Why Are Carbohydrates So Important?
Carbohydrates are the primary muscular fuel source for intense exercise
Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue
Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used
0
20
40
60
80
100
120
140
0 2 12 24 26 36 48 50 60 72
Time (hrs)
Mus
cle
Gly
coge
n (m
mol
/kg
wet
wt.
)High CHO Diet
(~575 g/d)
Low CHO Diet(~250 g/d)
Training Bouts (2 hrs)
Adapted from: Costill, 1985
Are athletes eating enough carbohydrates?
Recommendations for Training
Absolute CHO intakes should approach 350-600g/d or 5-10g/kg/d
The % of calories coming from CHO is not as important as long as absolute needs are met
16.3 16.6 16.5 15.8
52.745.451.844.5
3237.230.937.6
0
20
40
60
80
100
GeneralPopulation (M)
MarathonRunners (M)
GeneralPopulation (F)
MarathonRunners (F)
Per
cent
of
Tot
al E
nerg
y In
tak
eCHO FAT PRO
Adapted from: Nieman et al., 1989
Making Sense of CHO Recommendations
Body Wt. (kg) Kcal
CHO (%) CHO (g/d) CHO (g/kg)
70 4200 45 473 6.8
70 3700 60 560 8.0
70 2000 70 350 5.0
0
200
400
600
800
1000
1200
80% CHO Diet 43% CHO Diet
Tot
al C
HO
(g/
d)
12.1g/kg 6.5g/kg
4,675 kcal /d
4,675 kcal /d
Data from: Lamb et al., 1990
Typical CHO Intakes of Endurance Athletes
Subjects n CHO (g/d) CHO (%) Study
Distance Runners 10 396 49 Grandjean(1989)
Marathon Runners 19 487 52 Burke et al.,1991
Distance Runners 50 417 53 Williams,1992
Triathletes 25 627 60 Burke et al.,1991
Why Are Carbohydrates So Important?
Carbohydrates are the primary muscular fuel source for intense exercise
Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue
Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used
Carbohydrates consumed before, during, and after exercise maximize performance
Effect of CHO Feedings 2-4 hrs Before Exercise
Studies Exercise (+) Effect No Effect ( - ) Effect
7 (1987 –1999)
Cycling / Running at52 – 100% VO2max
4 2 1
Effect of CHO Feedings 30-60 min Before Exercise
Studies Exercise (+) Effect No Effect ( - ) Effect
11 (1979 –1994)
Cycling / Running at60 – 80% VO2max
3 4 3
Glycemic Index of Common Foods
High Moderate Low
Potato Banana Raisins Glucose Sucrose Bagel
Spaghetti Oatmeal Orange Grapes Potato Chips Sponge Cake
Apples Lentils Baked Beans Fructose Milk Tomato Soup
During & Early After Exercise
Before and Late After Exercise
Before and Late After Exercise
Effect of CHO Feedings During Exercise
Studies Exercise (+) Effect No Effect ( - ) Effect
19 (1984 –1998)
Cycling / Running at50 – 90% VO2max
17 1 1
Sports Drinks
Sports Drink CHO Type Concentration Calories (8 fl.oz.)
All Sport Sucrose,Fructose
8% 70
Exceed Glucose poly-mer, Fructose
7% 70
Gatorade Sucrose,Glucose
6% 50
PowerAde Fructose,Sucrose
8% 67
3
3.5
4
4.5
5
5.5
6
6.5
7
0 30 60 90 120 150 180 200
Time (min)
Pla
sma
Glu
cose
(m
mol
/L)
8% CHO
Placebo*
** * *
FATIGUE
Adapted from: McConell et al., 1999
3.4
3.6
3.8
4
4.2
5 10 15 20 25 30
Distance (km)
Ru
nnin
g S
pee
d (
m/s
ec)
CHO Trial (5% CHO drink)
Control Trial (water only)
Adapted from: Tsintzas et al., 1993
0
50
100
150
200
250
300
Placebo Pre-CHO Ex-CHO Both
Tim
e to
Exh
aust
ion
(min
) 18%
32%44%
Adapted from: Wright et al., 1991
Dorando Pietri, 1908 Olympic Marathon
Carbohydrates and Performance
Carbohydrates in the post-exercise period: Glycogen Resynthesis
82
91
86
70
40
50
60
70
80
90
100
Day 1 Day 2
Run
Tim
e (m
in)
at 7
0% V
O2m
axHigh CHO (9g/kg) Moderate CHO (6g/kg)
*
Adapted from: Fallowfield et al., 1993
Practical Recommendations
Time Period Carbohydrate Comments
Daily Training 5-10g/kg/d Dependent on intensity andduration of training
CHO Loading 5g/kg 3d, then>8g/kg 3d
For events > 90 min; depletingexercise then taper
Pre-Exercise 1-2g/kg 1-2 hr4-5g/kg 3-4 hr
Consume familiar foods
During Exercise .5-1g/kg/hr For events > 90 min; up to10% CHO solution
After Exercise .75-1.5g/kg/hr Begin as soon as possible forup to 4 hrs
Nutrition and Athletic Performance:Summary
• Number one nutritional priority is maintaining energy balance
• Athlete protein needs are higher than the RDA, but athletes* already consume even more than the upper scientific recommendations
• Carbohydrate needs are best expressed on a g/kg/d basis (or in absolute terms: 350-600g/d)
• Carbohydrates improve athletic performance for endurance exercise (> 90 continuous minutes)