Download Energy Systems for Exercise

Welcome to FCSN/PE 446
Sports Nutrition and Weight
Control
David L. Gee, PhD
www.cwu.edu/~geed
Energy Systems for
Exercise
FCSN/PE 446
Dr. David L. Gee
Professor of Food Science and Nutrition
Human Energy Systems
 ATP-PC
System
• adenosine triphosphate
• phosphocreatine
 Lactic
Acid System
• anaerobic glycolytic pathway
 Oxygen
System
• aerobic metabolic pathways
ATP-PC Energy System
ATP – Energy for muscle contraction
ATP-PC System
ATP
 highest
rate of energy
production
 lowest total energy capacity
 all energy for muscle
contraction must flow through
ATP
ATP-PC System
Phosphocreatine
 Rapid
equilibrium with ATP/ADP
 Highest rate of energy
production
 Lowest total energy production
Creatine as an Ergogenic Aid

Claims for creatine
(monohydrate)
• EAS web page
(2002)

“...may boost muscle size and
strength, increase lean body
mass, delay fatigue, and
speed muscle recovery after
exercise.”
Creatine as an Ergogenic Aid
Creatine
Loading Protocol
25-30 grams/day for 3-5 days
 3-5 grams/day for maintenance
 or 3-5 grams/day for gradual loading
 typical dietary creatine = 1g/d
 cost (EAS Phosphagen, 3/02)

• $16 for loading
• $36 per month for maintenance ($432/yr)
Is Creatine an Erogenic Aid?
 Levels
of evidence for
ergogenic effects
 1.
Is there a sound hypothetical
mechanism explaining potential
ergogenic effects?
Levels of evidence for
ergogenic effects
 2.
Are there biochemical
indicators that suggest
ergogenic effects?
 3. Are there studies that
demonstrate improvement of
physical performance?
Creatine as an Ergogenic Aid
 Theoretical
 creatine
Basis
phosphate levels limit ATP
production during maximal exercise
 Therefore, supplementation will
increase cellular CP levels and
increase high intensity performance
Creatine as an Ergogenic Aid
 Biochemical
evidence
 supplementation
of creatine does
result in increased muscle creatine
concentration
• 16% increase in muscle creatine after
6 day @ 20g/d
–Hultman et al, JAP 81:232-237 (1996)
Creatine as an Ergogenic Aid
 Scientific

Performance Evidence
Ideal investigation:
• RCT: Randomized Controlled Trials
– double blind - placebo trials


typically increases muscle Cr
typically results in increased LBM
• 0.7-1.6kg
• water or protein ?
• may impair performance
Creatine supplementation enhances muscular
performance during high-intensity resistant exercise.
JADA 97:765-770 (1997)

14 active men
• randomized, double blind w/ placebo
• 25g Cr/day for 6 days
• Tested on three occasions
– Before supplementation
– After 6 days of placebo capsule supplementation
– After 6 days of either placebo or creatine capsule
supplementation
• bench press (5 sets of 10 reps to failure)
• squat exercise (5 sets of 10 reps to failure)
A.
The placebo effect:
by set 4 & 5, athletes
taking placebo after
T2 and T3 have more
repetitions.
B.
The creatine effect:
by set 3, 4, & 5, athletes
consuming Cr perform
better than pre-supp (T1)
or placebo (T2)
A.
Placebo effect only seen
in set 2
B.
Creatine improves jumpsquat peak power output
in all sets over pre-supp
period (T1) and over
placebo (T2) in sets 1, 2,
3, & 4
Creatine supplementation enhances muscular
performance during high-intensity resistant exercise.
JADA 97:765-770 (1997)

Conclusion:
• One week of creatine supplementation
(25g/d) enhances muscular performance
during repeated sets of bench press and
jump squat exercise.
Creatine supplementation does not improve sprint
performance in competitive swimmers.
MSSE 28:1435-1441(1996)

28 trained competitive swimmers
• randomized, double-blind placebo trials
• 5 days 20g creatine/day or placebo
• 25, 50, 100 meter trials, best stroke

Results
• no significant differences in performance
times between trials or groups
• no effect of Cr on post-exercise blood
lactate
Creatine as an Ergogenic Aid
 Many,
but not all studies
show increases in power
output
 generally seen in high power,
repetitive exercise tests
Creatine as an Ergogenic Aid
 No
(?) long term safety tests
• No consistent reports of
adverse affects
 Few
studies with
adolescents
 Recommendations?
ACSN Consensus Statement
Creatine Supplementation
MSSE March 2000
 Oral Cr increases muscle C~P
 3g/d over time = 20g/d loading
 “Exercise performance involving short
periods of extremely powerful activity
can be enhanced, especially during
repeated bouts of activity.”

ACSN Consensus Statement
Creatine Supplementation



“There is no definitive evidence that Cr
supplementation causes GI, renal, and/or
muscle cramping”
“…Cr exhibits small but significant
physiological and performances
changes…are realized during very specific
exercise conditions”
“”…apparent high expectations…are
inordinant.”
Creatine as an Ergogenic Aid
Miscellaneous information

Creatine kinase
• ineffective as oral supplement
• blood levels indicate muscle damage

Creatinine
• waste product of creatine metabolism
• blood levels reflect renal function
• urine levels reflect
– Total muscle mass
– Dietary intake of creatine
CK
Dietary Supplements as Ergogenic Aids:
Let the Buyer Beware!


Dietary Supplement Health Education Act
(DSHEA)
Labeling of dietary supplements follow same
laws as for foods (NLEA).
• Only approved health claims allowed
• “structure/function” claims allowed

Unlike pharmaceutical drug regulations
• No proof of safety required
• No proof of effectiveness required
• No effective regulation of product contents or
purity
Dietary Supplements:
The NFL Player’s Association Recommendation
http://www.nflpa.org/members/main.asp?subPage=Steroid+Policy

As the Policy clearly warns, supplements are not regulated or
monitored by the government. This means that, even if they
are bought over-the-counter from a known establishment, there
is simply no way to be sure that they:
• (a) contain the ingredients listed on the packaging;
(b) have not been tainted with prohibited substances; or
(c) have the properties or effects claimed by the manufacturer or
salesperson.

Therefore, if you take these products, you do so AT YOUR
OWN RISK! The risk is at least a 4-game suspension without
pay if a prohibited substance is detected in your system. For
your own health and success in the League, we strongly
encourage you to avoid the use of supplements altogether, or at
the very least to be extremely careful about what you choose to
take.
NCAA: Permissible Nutritional Supplements
NCAA Bylaw 16.5.2.2 (2000) (web page link)

Supplements NCAA institutions can provide
to athletes
• Non-muscle building nutritional supplements
–
–
–
–

Vitamins and minerals
Energy bars
Calorie replacement drinks (Ensure, Boost)
Electrolyte replacement drinks (Gatorade, Powerade)
Non-Permissible
•
•
•
•
creatine
Amino acids
Carnitine
Protein-powders and others
Lactic Acid System
Anaerobic
 Uses
glycolysis
muscle glycogen, blood
glucose, liver glycogen as
substrates (not FAT or PRO)
 High rate of ATP energy production
 Primary fuel in sprint-type activities
(a few seconds - few minutes)
Lactic Acid System
 Important

when:
Activity longer than a few seconds
• creatine-P depleted/limited

Activity too intense for aerobic
metabolism
• oxygen delivery limited
– limited rate of O2 :
• uptake in lung
• transport and delivery to muscle cell
• transport and delivery to mitochondria
Lactic Acid System
Lactic acid is the end product
 Low total energy capacity

• lactic acidosis
• Inhibits glycolytic enzymes

Training effects
• improved aerobic capacity reducing lactate
production
• improved removal of lactate

Ergogenic aids
• bicarbonate loading
Oxygen Energy System
Oxygen Energy Systems
 Aerobic
carbohydrate
metabolism
• glycolysis, Krebs cycle, electron transport
system
lower rate of ATP energy production
 high total energy capacity
 primary source of energy for higher
intensity endurance events (~< 30 min)

09.06 Aerobic Respiration Overview
Slide number: 2
Glucose
Plasma
membrane
Mitochondrion
Cytoplasm
Extracellular fluid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
09.06 Aerobic Respiration Overview
Slide number: 4
Glucose
Glycolysis
Pyruvate
ATP
NADH
Acetyl-CoA
NADH
Plasma
membrane
Mitochondrion
Cytoplasm
Extracellular fluid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
09.06 Aerobic Respiration Overview
Slide number: 6
Glucose
Glycolysis
Pyruvate
ATP
NADH
Acetyl-CoA
Krebs
cycle
NADH
H2O
ATP
NADH
Plasma
membrane
Mitochondrion
Cytoplasm
ATP
Extracellular fluid
CO2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
O2
Oxygen Energy Systems
 Fat
oxidation
• Beta-oxidation, Krebs cycle, Electron
transport system
Lowest rate of ATP-energy production
 Highest total energy capacity
 Primary source of energy during lower
intensity endurance events (~>30 min)

Oxygen Energy Systems
 Protein
oxidation
• Amino acid oxidation, Krebs cycle, Electron
transport system
Low rate of ATP-energy production
 Limited total energy capacity
 significant source of energy during long
endurance events

% Contribution of Aerobic and
Anaerobic Energy Sources
Human Energy Stores
Sources of energy for energy systems
ATP-PC
Carbohydrates
• Muscle glycogen
• Blood glucose
• Liver glycogen
Human Energy Stores
Fats
- Triglycerides
• Adipose triglycerides
• Muscle triglyceride

Hormone sensitive lipase
• Activity enhanced with caffeine

Ketone bodies
• partially oxidized fatty acids
• produced in liver, burned in muscle
• significant source of energy during prolonged
endurance exercise
Human Energy Stores
Proteins
 direct muscle oxidation
(branched chain amino
acids)
 gluconeogenesis in liver from
amino acids
Exercise Energy Metabolism:
 Examples
data
of experimental
Exercise Energy Metabolism:
Examples of
experimental data
Example 1:
Metabolic Fuels During
Intense Exhaustive Exercise
3
one minute sprints with one
minute rest
 muscle needle biopsy
• prior to
• 15 sec post-exhaustion (exhaustion)
• 30 minutes post-exhaustion
(recovery)
Example 1:
Metabolic Fuels During
Intense Exhaustive Exercise
initial
ATP
(umol/g)
4.6
PC
(umol/g)
17
exhaustion
3.4
3.7
recovery
4.0
18.8
Example 1:
Metabolic Fuels During
Intense Exhaustive Exercise
Glycogen
Lactate
initial
88 ug/g
1.1 umol/g
exhausted
58
30.5
recovery
70
6.5
Key Points

In repeated one minute sprints
• Lactic acid system primary source of fuel
• [lactic acid] increases 30-fold resulting in
lactic acidosis
• ATP & C~P are regenerated quickly after
exercise
• Elevated lactate seen 30 minutes after
exercise
Example 2:
Glycogen Utilization During
Endurance Exercise

Protocol
•
•
•
•
Trained and untrained runners
Treadmill running at ~ 70% VO2 max
Run to exhaustion
Measure muscle glycogen content every
20 minutes until exhaustion
Example 2:
Glycogen Utilization During
Endurance Exercise
Minutes
exercise
0
20
40
60
80
90
Glycogen
(untrained)
94 (umol/g)
39
22
11
0.6 (exhausted)
Glycogen
(trained)
100 (umol/g)
55
39
14
11
0.2 (exhausted)
Key Points
Glycogen primary source of fuel in
exercise lasting 60-90 minutes
Glycogen depletion associated with
fatigue
Rate of glycogen utilization rate higher
early in exercise, lower late in exercise
Utilization of glycogen lower in trained
athletes
Example 3:
Glycogen Degradation Rate During
Exercise

Protocol
• Trained and untrained subjects
• Treadmill running at different % VO2 max
• Muscle biopsies to determine rate of
muscle glycogen utilization
Example 3:
Glycogen Degradation Rate During
Exercise
80
70
glycogen degradation rate
60
50
Trained
40
Untrained
30
20
10
0
0
10
20
30
40
50
% VO2 max
60
70
80
90
Key Points
Rate of glycogen utilization directly
related to intensity of exercise
 Trained athletes utilize glycogen at
lower rates than untrained subjects at
same relative %VO2

• More efficient delivery of oxygen and
mobilization/oxidation of stored fats.
Example 4:
Effect of Glycogen Level on Rating of
Perceived Exertion

Protocol
•
•
•
•
Trained runners
Treadmill test at %70% of VO2max
Muscle biopsies for glycogen determination
RPE evaluation
Key Points
Glycogen utilization rate highest early in
exercise
 Muscle glycogen concentration
inversely related to rating of perceived
exertion

Example 5:
Effect of Initial Muscle Glycogen Levels
and Endurance
 Protocol
• Fed trained athletes diets for 4 days
either
–Low (10%)
–Moderate (50%)
–high carbohydrate (85%)diets
• Treadmill running at 65% VO2max
• Muscle biopsy for glycogen analysis
prior to treadmill run
Example 5:
Effect of Initial Muscle Glycogen Levels and
Endurance
200
180
High carb diet
Time to exhaustion (min)
160
140
120
Moderate carb diet
100
80
60
Low carb diet
40
20
0
0
0.5
1
1.5
2
2.5
initial muscle glycogen (g/100g)
3
3.5
4
Key Points
Initial Glycogen Levels and Endurance
During treadmill running, time to
exhaustion is correlated with initial
muscle glycogen content
 Muscle glycogen content is affected by
diet

• High carb diets promote glycogen storage
Example 6a:
Muscle Glycogen and Soccer Performance
(Agnevik, 1970)
1.2
1
mg glycogen/100g
0.8
0.6
0.4
0.2
0
Pre-game
Half-time
Post-game
Example 6b:
Muscle Glycogen and Soccer Performance
Saltin, 1973
14000
12000
time (seconds)
10000
8000
Walking
Running
Total
6000
4000
2000
0
High Glycogen
Low Glycogen
Key Points
Diet and Soccer Performance
Glycogen depletion is possible during
soccer play
 Initial glycogen content affects time
spent running and total active time

• High glycogen allows for more running and
total activity during soccer games
Example 7:
Effect of Successive Days of Intense Training on
Glycogen Content
Costill & Miller (1980)
Trained endurance runners
 3 successive days of running 10 miles
at 80% of VO2 max
 Dietary intake of CHO

• 58% of Calories
• 70% of Calories
Example 7:
Effect of Successive Days of Intense Training on
Glycogen Content
Costill & Miller (1980)
140
Muscle glycogen (mmol/kg ww)
120
100
80
High CHO
Low CHO
60
40
20
0
0
10
20
30
40
Time (hours)
50
60
70
80
Key Points:
Effect of Successive Days of Intense Training on
Glycogen Content

Glycogen depletion can occur with
successive days of intense training
• Even when individual training day is not
glycogen depleting

High carbohydrate diets promote
replacement of glycogen used during
exercise
• Helps prevent glycogen depletion during
successive days of training
Metabolic Causes of Fatigue During
Exercise.
Table 3.9 (Williams)
 Decreased
Levels of Energy
Substrates
 decreased
phosphocreatine levels
 decreased muscle glycogen
 decreased blood glucose
• hypoglycemia
Metabolic Causes of Fatigue During
Exercise.
Table 3.9 (Williams)

Decreased Levels of Energy Substrates
(cont.)

decreased blood branch-chain amino acids
• Significant source of energy for muscle during endurance
exercise
• Central Fatigue Hypothesis (increased formation of
depressant neurotransmitters)
–
–
–
–
–
–
Decreased blood BCAA during exercise
Increase blood tryptophan:BCAA ratio
Shared blood:brain barrier transport system
Increased brain tryptophan
Increased synthesis of serotonin from tryptophan
Increased feeling of fatigue
Metabolic Causes of Fatigue
During Exercise.
 Disturbed
Acid-Base Balance
• lactic acidosis
 Decreased
Oxygen Transport
• decreased blood volume due to
dehydration
• High altitudes
• Nutritional anemias
Metabolic Causes of Fatigue
During Exercise.
 Increased
Core Body
Temperature
• dehydration
• environmental conditions
 Disturbed
Electrolyte Balance
• high sweat loss
• no electrolyte replacement