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Exercise Physiology MPB 326. David Wasserman, PhD Light Hall Rm 823 3-7336. The Remarkable Thing about Exercise. The Great Debate. Top-down Feedback control. Energy Metabolism and the Three Principles of Fuel Utilization.

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exercise physiology mpb 326

Exercise PhysiologyMPB 326

David Wasserman, PhD

Light Hall Rm 823

3-7336

the great debate
The Great Debate
  • Top-down
  • Feedback control
slide5
The need for energy starts when calcium is released from the sarcoplasmic reticulum of contracting muscle
sources of atp
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

slide11

ATP-PCr (Phosphagen system)

Stored in the muscle cells (PCr > 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

glycolysis
Glycolysis

Glucose + 2 ADP + 2 Pi + 2 NAD+

2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

lactate dehydrogenase
Lactate Dehydrogenase

Hypoxic conditions

Pyruvate + CoA + NADH + H+

Lactate + NAD+

pyruvate dehydrogenase
Pyruvate Dehydrogenase

Lots of Oxygen

Pyruvate + CoA + NADP+

Acetyl-CoA + CO2 + NADPH

pyruvate dehydrogenase1
Pyruvate Dehydrogenase

Pyruvate + CoA + NADP+

Acetyl-CoA + CO2 + NADPH

tca cycle
TCA Cycle

Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 2H20

CoASH + 3 NADH + 3H+ + FADH2 + GTP + 2CO2

beta oxidation of fatty acids
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+

summary of atp production via lipid oxidation
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

energy for burst and endurance activities
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 glycolysis…1.3 to 1.6 min
  • aerobic system.........unlimited time(as long as nutrients last)
aerobic energy
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
oxygen uptake and exercise domains

I

N

C

R

E

M

E

N

T

A

L

4

VO2 (l/min)

Severe

2

Heavy

Moderate

0

150

300

Work Rate (Watts)

Oxygen Uptake and Exercise Domains
anaerobic threshold concept

Heart

Disease

Onset of lactic acidosis

Athlete

Anaerobic Threshold Concept

Exercise

15

Blood

Lactate

mM

10

5

0

150

50

100

200

250

Rest Period

Exercise

(watts)

anaerobic threshold in some elite long distance athletes can be close to max

Bill

Rodgers

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

20

40

Basal

Oxygen

Uptake

80

100

Oxygen Uptake

(% maximum)

oxygen uptake and exercise domains1
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)

lactate and exercise
Lactate and Exercise

12

Blood Lactate

mM

6

0

12

24

0

Time (minutes)

three principles of fuel utilization during exercise
Three Principles of Fuel Utilization during Exercise
  • Maintaining glucose homeostasis
  • Using the fuel that is most efficient

Storage

Metabolic

  • Preserving muscle glycogen core
glucose homeostasis is usually maintained despite increased glucose uptake by the working muscle
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

)

carbohydrate stores after an overnight fast sedentary
Carbohydrate Stores after an Overnight FastSedentary

100

grams

Liver

Glycogen

Blood

Glucose

Muscle

Glycogen

400

grams

4 grams

carbohydrate stores after an overnight fast 1 hr of exercise
Carbohydrate Stores after an Overnight Fast 1 hr of Exercise

Liver

Glycogen

Blood

Glucose

Muscle

Glycogen

400

grams

4 grams

100

grams

carbohydrate stores after an overnight fast 2 hr of exercise
Carbohydrate Stores after an Overnight Fast 2 hr of Exercise

Liver

Glycogen

Blood

Glucose

Muscle

Glycogen

400

grams

4 grams

100

grams

carbohydrate stores after an overnight fast 3 hr of exercise
Carbohydrate Stores after an Overnight Fast 3 hr of Exercise

Liver

Glycogen

Blood

Glucose

Muscle

Glycogen

400

grams

4 grams

100

grams

carbohydrate stores after an overnight fast 4 hr of exercise
Carbohydrate Stores after an Overnight Fast 4 hr of Exercise

Liver

Glycogen

Blood

Glucose

Muscle

Glycogen

400

grams

4 grams

100

grams

!!!

contribution of different fuels to metabolism by the working muscle is determined by 3 objectives
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
the most efficient fuel depends on exercise intensity and duration
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 O2than fatmetabolism.

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.

effects of exercise intensity
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.

effects of exercise duration
Effects of Exercise Duration

From: Powers & Howley. (2007). Exercise Physiology. McGraw-Hill.

fuel selection
Fuel Selection
  • As intensity increases carbohydrate use increases, fat use decreases
  • As duration increase, fat use increases, carb use decreases

From: Powers & Howley. (2007). Exercise Physiology. McGraw-Hill.

contribution of different fuels to metabolism by the working muscle is determined by 3 objectives1
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
slide45
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.

contribution of different fuels to metabolism by the working muscle is determined by 3 objectives2
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
discussion question
Discussion Question

Can you accommodate all three principles of fuel utilization?

Why not?

What is the Consequence?

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