Exercise Physiology MPB 326

1
Exercise PhysiologyMPB 326

• David Wasserman, PhD
• Light Hall Rm 823
• 3-7336

2
The Remarkable Thing about Exercise
3
The Great Debate

• Top-down
• Feedback control

4
Energy Metabolism and the Three Principles of
Fuel Utilization
5
The need for energy starts when calcium is
released from the sarcoplasmic reticulum of
contracting muscle
6
The Working Muscle
7
Energy for Contraction
8
Muscle relaxation requires energy too!
9
Where does this ATP come from?
10
Sources of ATP

• Stored in muscle cell (limited)
• Synthesized from macronutrients
• Common Processes for ATP production
• Anaerobic System
• a. ATP-PC (Phosphagen system)  
• b. Anaerobic glycolysis (lactic acid system)
• Aerobic System
• a. Aerobic glycolysis
• b. Fatty acid oxidation
• c. TCA Cycle

11
ATP-PCr (Phosphagen system)

• Stored in the muscle cells (PCr gt ATP)
• ATP H2O ? ADP Pi E (ATPase hydrolysis)
• PCr ADP ? ATP Cr (creatine kinase reaction)
• ADP ADP ? ATP AMP (adenylate kinase)
• PCr represents the most rapidly available source
  of ATP
• a) Does not depend on long series of reactions
• b) No O2 transportation required
• c) Limited storage, readily depleted 10 s

12
Glycolysis
Glucose 2 ADP 2 Pi 2 NAD 2
Pyruvate 2 ATP 2 NADH 2 H 2 H2O
13
Lactate Dehydrogenase
Hypoxic conditions
Pyruvate CoA NADH H Lactate NAD
14
Pyruvate Dehydrogenase
Lots of Oxygen
Pyruvate CoA NADP Acetyl-CoA CO2 NADPH
15
Pyruvate Dehydrogenase
Pyruvate CoA NADP Acetyl-CoA CO2 NADPH
16
TCA Cycle
Acetyl-CoA 3 NAD FAD GDP Pi
2H20 CoASH 3 NADH 3H FADH2
GTP 2CO2
17
Beta Oxidation of Fatty Acids
7 FAD 7 NAD 7 CoASH 7 H2O
H(CH2CH2)7CH2CO-SCoA 8 CH3CO-SCoA 7 FADH2
7 NADH 7 H
18
Summary of ATP Production via Lipid Oxidation

• ATP Balance Sheet for Palmitic Acid (16
  carbon) ATP
• Activation of FA chain -1
• ß oxidation (16 Carbons / 2) 1 7 (at 5 ATP
  each) 35
• Acetyl-CoA (16 Carbons / 2) 8 (at 12 ATP
  each) 96
• Total per chain 130

19
Electrochemical Energy and ATP Synthesis
20
Energy for Burst and Endurance Activities

• Rate of ATP Production (M of ATP/min)
• phosphagen system ..............4
• anaerobic glycolysis..2.5
• aerobic system.......................1

• How long Can it Last?
• phosphagen system...8 to 10 sec
• anaerobic glycolysis1.3 to 1.6 min
• aerobic system.........unlimited time (as long as
  nutrients last)

21
(No Transcript)
22
Aerobic Energy

• During low intensity exercise, the majority of
  energy is provided aerobically
• Energy produced aerobically requires O2
• Therefore, O2 uptake can be used as a measure for
  energy use

23
Exercise Testing in Health and Disease
24
Oxygen Uptake and Exercise Domains
25
Anaerobic Threshold Concept
Exercise
15
Blood Lactate mM
10
5
0
150
100
50
250
200
Rest Period
Exercise
(watts)
26
Anaerobic Threshold in Some Elite Long Distance
Athletes can be close to Max
Exercise
15
Onset of lactic acidosis
Blood Lactate mM
10
5
0
60
40
20
100
80
Basal Oxygen Uptake
Oxygen Uptake
( maximum)
27
Oxygen Deficit and Debt
28
Oxygen Uptake and Exercise Domains
C
O
N
S
T
A
N
T

L
O
A
D
Severe
4
Heavy
2
Moderate
0
12
24

Time (minutes)
29
Lactate and Exercise
12
Blood Lactate mM
6
0
12
24
0
Time (minutes)
30
Three Principles of Fuel Utilization during
Exercise

• Maintaining glucose homeostasis
• Using the fuel that is most efficient
• Storage
• Metabolic
• Preserving muscle glycogen core

31
Glucose homeostasis is usually maintained despite
increased glucose uptake by the working muscle
Moderate
Exercise
1
0
0
8
0
Blood
6
0
Glucose
(
mg
/
dl
)
4
0
2
0
0
5
4
R
a
t
e
s

o
f

G
l
u
c
o
s
e
E
n
t
r
y

a
n
d
E
n
t
r
y
3
R
e
m
o
v
a
l

f
r
o
m
t
h
e

B
l
o
o
d
2
R
e
m
o
v
a
l
-
1
-
1
(
m
g

k
g

m
i
n
)
1
0
-
3
0
0
3
0
6
0
T
i
m
e

(
m
i
n
)
32
Carbohydrate Stores after an Overnight
FastSedentary
Liver Glycogen
Blood Glucose
Muscle Glycogen
400 grams
4 grams
33
Carbohydrate Stores after an Overnight Fast 1 hr
of Exercise
Liver Glycogen
Blood Glucose
Muscle Glycogen
400 grams
4 grams
100 grams
34
Carbohydrate Stores after an Overnight Fast 2 hr
of Exercise
Liver Glycogen
Blood Glucose
Muscle Glycogen
400 grams
4 grams
100 grams
35
Carbohydrate Stores after an Overnight Fast 3 hr
of Exercise
Liver Glycogen
Blood Glucose
Muscle Glycogen
400 grams
4 grams
100 grams
36
Carbohydrate Stores after an Overnight Fast 4 hr
of Exercise
Liver Glycogen
Blood Glucose
Muscle Glycogen
400 grams
4 grams
100 grams
!!!
37
Contribution of different fuels to metabolism by
the working muscle is determined by 3 objectives

• Maintaining glucose homeostasis
• Using the fuel that is most efficient
• Storage
• Metabolic
• Preserving muscle glycogen core

38
The Most Efficient Fuel depends on Exercise
Intensity and Duration

• Metabolic Efficiency
• CHO is preferred during high intensity exercise
  because its metabolism yields more energy per
  liter of O2 than fat metabolism.
• kcal/l of O2
• CHO 5.05
• Fat 4.74
• CHO can also produce energy without O2!!!
• Storage Efficiency
• Fat is preferred during prolonged exercise
  because its metabolism provides more energy per
  unit mass than CHO metabolism.
• kcal/g of fuel
• CHO 4.10
• Fat 9.45
• Fats are stored in the absence of H2O.

39
Effects of Exercise Intensity

• Plasma FFA (fat from fat cells) is the primary
  fuel source for low intensity exercise
• As intensity increases, the source shifts to
  muscle glycogen

From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
40
Effects of Exercise Duration
From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
41
Fuel Selection
From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.

• As intensity increases carbohydrate use
  increases, fat use decreases
• As duration increase, fat use increases, carb use
  decreases

42
Contribution of different fuels to metabolism by
the working muscle is determined by 3 objectives

• Maintaining glucose homeostasis
• Using the fuel that is most efficient
• Storage
• Metabolic
• Preserving muscle glycogen core

43
(No Transcript)
44
(No Transcript)
45
Other fuels are utilized to spare muscle glycogen
during prolonged exercise thereby delaying
exhaustion
Adipose
Lactate
NEFA
Pyruvate
Glycerol
Amino Acids
Muscle
NEFA
GLY
ATP
GNG
GLY
Glucose
Liver
As exercise duration increases
More energy is derived from fats and less from
glycogen.
Amino acid, glycerol, lactate and pyruvate
carbons are
recycled into glucose.
46
Contribution of different fuels to metabolism by
the working muscle is determined by 3 objectives

• Maintaining glucose homeostasis
• Using the fuel that is most efficient
• Storage
• Metabolic
• Preserving muscle glycogen core

47
Discussion Question

• Can you accommodate all three principles of fuel
  utilization?
• Why not?
• What is the Consequence?