Download Chap 84 - Exercise Physiology

Exercise Physiology
Physiology III, Tri 4
Mrs. Brashear
Objectives: The student should learn:
1. The response of skeletal muscle to acute and chronic exercise
2. The types of muscle contraction
3. The types of training
4. The response and adaptation of the respiratory system to exercise
References:
Guyton & Hall, chapter 84
Resource Manual, American College of Sports Medicine
I. Introduction
A. Differences between male and female athletes
1. Strength per square centimeter of muscle cross-sectional area
2. Differences in total muscle performance
B. Muscle metabolism - 3 major energy systems
1. Phosphagen system
a. ATP basic source of energy for muscle contraction
b. 3 second supply- constant need for ATP production from
1. creatine phosphate – 5 – 10 second supply
2. glycogen
c. fuel:
1. glucose
2. fatty acids
3. amino acids
d. Used for: 100 meter dash, diving, weight lifting, etc.
2. Glycogen-Lactic acid system
a. anaerobic
b. production of lactic acid from stored glycogen
c. energy production fast
d. lasts short time 1.3 – 1.6 minutes of max. muscle activity
3. Aerobic system
a. unlimited at submaximal levels of exercise
b. slower ATP production from oxidative processes
c. fuel:
1. glucose
2. fatty acids
3. amino acids
C. Recovery of muscle metabolism after exercise
1. Removal of lactic acid
a. cells convert to pyruvic acid
b. liver converts lactic acid to glucose
2. Recovery of aerobic systems
a. oxygen debt – repay oxygen used during exercise
.5 L –lungs, 1 L – hemoglobin, .25 L dissolved, .3 L –myoglobin
9 L to replenish phosphagen and lactic acid system
b. Muscle glycogen
What kind of diet is needed to replace glycogen?
c. Nutrients used during exercise
1. initially CHO
2. at point of fatigue almost all lipids
II. Responses and Adaptations of Skeletal Muscle to Exercise
Type I or Slow Oxidative
Contract slowly
Fatigue resistant
Aerobic
Small diameter
Small force
IIa or Fast Oxidative-Glycolytic
Intermediate contraction
Intermediate fatigue resistant
Aerobic/anaerobic
Large diameter
Large force
II b or Fast Glycolytic
Fast Contraction
Marked fatigue
Anaerobic
Large diameter
Large force
A. Review of Muscle types – “fast” vs. “slow”
1. force/x-section almost the same for type I and II fibers
2. proportion of fast and slow fibers determined genetically
3. can alter some biochemical and structural properties of both fiber types
with
training
B. Taxonomy of Contraction
Training procedures are classified according to the type of muscle contraction.
Three variables characterize contraction of muscle:
a. time and duration of contraction (velocity)
b. displacement of muscle (length change)
c. force produced or mass or object moved
1. Isometric – static exercise force development – no displacement
a. degree of displacement of limb or rotation of joint = 0
b. isometric training – develops strength in a particular movement
c. strength is highly specific to joint angle exercise is performed
d. important to counteract strength loss and atrophy from
immobilization.
Bone loss & lean body mass during dieting, osteoporosis
e. negative – anaerobic, high afterload, concentric hypertrophy of the
heart, no aerobic benefits
2. Isotonic – dynamic exercise force development + displacement
a. force production is constant experimentally
b. used to gain strength and endurance
c. can be aerobic and anaerobic
d. types of contractions
1) concentric – force development during muscle shortening
2) eccentric – force development during muscle lengthening
3. Isokinetic
a. rate of displacement is constant – constant velocity of lengthening or
shortening
b. rarely occurs in the human body
c. use special equipment that allows muscles to develop maximum
tension as it shortens at a constant speed through a complete range
of motion
d. combines features of isometric and isotonic muscle overload at
preset speed
e. can achieve max tension development or force output at any point in
the range of motion
f. same type of training as isotonic ( 3 sets, 5 –10 reps, 3-5
times/week)
g. used in rehab
Isotonic and isokinetic can be maintained at an aerobic pace and build
strength and endurance, maintain bone density and lean body mass.
C. Effects of Training – skeletal muscle adapts to an increase in load
* Major objective to training is to cause biological adaptations to improve
performance in a specific task
* Specific adaptation is determined by the mode (type of training), frequency
of the exercise, intensity and duration of the exercise
* Skeletal muscle adaptations are characterized by morphological,
biochemical and molecular variable that alter fibers in specific motor units
* Adaptations are readily reversible when the exercise stimulus is removed –
detraining
* Specificity of training – specific to motor units
1. Endurance training – prolonged work of moderate intensity (submaximal)
dependent on oxidative capacity of muscles
a. Endurance training produces an increase in aerobic capacity
(Vo2 max), increase in the number and size of mitochondria.
Increases the
oxidative capacity for all fuel types
1) slow oxidative fibers – greatest increase in oxidative
capacity
2) fast glycolytic-oxidative – medium increase
3) fast glycolytic – least oxidative adaptation, little or no
increase in mitochondria
b. Increase in fatty acid utilization – spares glycogen as a fuel
source in prolonged exercise
1) 20 minutes to mobilize fats from adipose tissue
2) severe levels of exercise – use CHO
c. increase capillarity and increase in the diameter of blood vessels
in muscles
d. increase in VO2 max = increase in aerobic capacity
* Endurance training leads to the ability to perform a higher level of work
for extended period and delay fatigue during submaximal work
2. Sprint Training
* Object is to recruit fast glycolytic-oxidative fibers to do high intensity
anaerobic work at or near the level of fast glycolytic fibers
* Increase rate through the glycolytic pathway by increasing the
performance of enzymes
* May increase glycogen storage
* May increase oxidative enzymes, # and size of mitochondria in slow and
fast glycolytic-oxidative fibers
a. slow oxidative – least change in glycolytic flux
b. fast glycolytic-oxidative – medium changes
c. fast glycolytic increase in enzymes and increase in flux
* Increases CHO utilization from glycogen
* Muscle hypertrophy in legs
3. Strength Training
Object: increase maximal force development capacity in skeletal muscle
a. increase in muscle size and strength
b. new sarcomeres in parallel in existing myofibrils
c. increase in strength is related to increase in X-section of muscle
d. X-section and strength of connective tissue also increases
e. hypertrophy primarily in fast glycolytic fibers. Moderately in
FG-O fibers
f. increase in glycolytic enzymes and flux through glycolysis
1) slow oxidative – least adaptation
2) fast glycolytic-oxidative – moderate increase in glycolytic
abilities, decrease in mitochondria
3) fast glycolytic - significant glycolytic changes, sig. decrease
in mitochondria
g. increase CHO utilization from glycogen stores
h. muscle hypertrophy
i. decrease vascularity relative to surface area of muscle fibers
III. Respiratory Response to Exercise
Introduction : Stresses on Respiration
A. Mechanics of Breathing
1. Work of Breathing
a. inc. in tidal volume = inc. in compliance work
b. inc. airway resistance work
c. inc. resistance to air movement through nasal passages
B. Changes in Ventilation
1. inc. rate and depth of breathing
a. mild to moderate levels of exercise
b. above the anaerobic threshold
2. inc. to 40-50 breaths/minute
3. tidal volume inc. to about 50-60% of VC
4. arterial oxygen and carbon dioxide conc. remain stable until anaerobic
threshold is exceeded
C. Pulmonary Blood Flow
1. Passive inc. in C.O. = inc. in pulmonary flow
slight inc. in PMAP
2. VA/Q - becomes more uniform and nearer to ideal
D. Diffusing Capacity of Alveoli
1. inc. surface area
2. inc. flow & velocity of flow
3. conc. gradient for diffusion changes
E. Oxygen and Carbon Dioxide Transport
1. HbO2 dissociation curve shift to the right
2. conc. gradient changes
3. exhaustive exercise -- maintain 93-94% Hb saturation
IV. Respiratory Adaptations to Exercise
A. Ventilation
1. resting unchanged
2. total lung capacity unchanged
3. VC may or may not change
4. inc. in respiration linked to the effect of training
V. Introduction to Cardiovascular Responses and Adaptation to Exercise
A. Increase in cardiac output
1. metabolic needs
2. prevent hyperthermia
3. protection of flow to essential organs
B. CV response to different types of exercise is not the same
C. Control of CV changes during exercise
1. Neural control
a. Central command – cerebrocortical activation
initial response to exercise
b. Reflexes originating in the muscle – peripheral control
Exercise pressor reflex – mechanoreceptors for stretch and tension
1) Group III myelinated fibers
2) Group IV unmyelinated fibers
c. Baroreceptors – regulation of blood pressure
2. Local control – metabolic control
a. coronary circulation
b. skeletal muscle
D. Determinates of Cardiac Ventricular Function
1. Preload
2. Afterload
3. Contractility
4. Heart rate
VI. Cardiovascular Responses and Adaptations to Dynamic or Isotonic Exercise
A. Cardiac output
1. Heart rate – maximum is age dependent
2. Stroke volume
B. Peripheral changes
1. distribution of blood – see chart
2. TPR
3. Arterial blood pressure changes
a. systolic pressure
b. diastolic pressure
c. pulse pressure and MAP
4. Arterio-venous oxygen difference (A-Vo2 diff)
Rest = 4-5 ml. oxygen/dl of blood
max. intensity exercise = 13 –16 ml. oxygen/dl of blood
5. Thermoregulation
a. moderate level exercise
b. severe level exercise
C. Cardiovascular Adaptations to Chronic or Endurance Isotonic Exercise
1. VO2 max
2. Blood
a. volume
b. hemoglobin
c. viscosity
3. Heart
a. vasculature
b. musculature
c. heart rate
d. stroke volume
e. oxygen demands
4. Peripheral vasculature
D. Effects of Endurance training on Cardiovascular Function
1. Atherosclerosis
2. HDL-LDL
3. Hypertension
4. Obesity
VII. Cardiovascular Responses to Isometric Exercise
A. Blood flow during exercise
1. muscle
2. periphery
B. CV effects
1. blood pressure
2. systolic
3. diastolic
4. afterload - cardiac muscle hypertrophy
5. TPR
VIII. Responses of Other Systems to Exercise
A. GI tract
1. acute
2. Chronic
B. Renal
1. acute
2. chronic
C. Skeletal
1. acute
2. chronic
D. Endocrine
1. Changes in GH, cortisol, glucagon, insulin, estrogen and testosterone based
on the level of exercise
2. Endocrine effects on metabolism during exercise
E. Immune Response
1. acute
2. chronic
EXERCISE PHYSIOLOGY CHARTS
Energy Utilization
100
% Energy
Contribution
Creatine phosphate
75
Mitochondrial
Respiration
Glycolytic
50
25
0
.05
1
1.5
2
2.5
3
3.5
The relationship between exercise duration and energy usage.
Oxygen Debt
5
4
Rate of O2
Uptake (L/min)
Exercise
3
2
Alactacid oxygen debt = 3.5 L
1
Lactic acid oxygen debt = 8 L
0
0
4
8
12
16
20 24 28
TIME (min)
32
36
40
44
Oxygen uptake for four minutes of exercise and then for almost an hour after
exercise is over.
Effect of diet on exercise
100
75
%CHO
CHO diet
EXHAUSTION
0
25
%Fat
usage

50
50
usage

25
75

0
0
10
20
Seconds
40
2 4
Minutes
100
1 2 3 4
Hours
The effect that diet has on the type of energy used for exercise and the duration of
exercise.
Muscle glycogen replinishment
2 hours of exercise
24
20
Muscle
glycogen
content


High CHO diet

16

12
(gm/kg)

8
4
No Food
0
0
10
20
30
40
50
Effect of diet on muscle glycogen replenishment.
Effect of Exercise on Respiration
EXERCISE

 oxygen consumption
 carbon dioxide production
5 days
 ventilation
Arterial Blood
No change PO2
No change PCO2
No change or  in pH
Venous Blood
 PCO2
Pulmonary Blood
Flow
CO
Shifts to the right
 Pulmonary flow affinity for O2
V/Q more even
in lungs
 in dead space
Effect of Exercise on Respiration
Alveolar Ventilation
L/min
Arterial PO2
mm Hg
100 Anaerobic Threshold
80
60
40
20
0
100
90
80
40
O2-Hemoglobin
Curve
Arterial PCO2
mm Hg
30
Total [H+]
(mM/L)
60
48
36
Rest
Work Maximal
Changes in Respiratory Volumes
6
90
5
IRV
70
4
Volume
(liters)
% of Vital
50 Capacity
3
Tidal Volume
30
2
10
1
FRC
RV
0
0
10
20
30
40
50
60
Regulation of CV function during exercise
Exercise
Central Command
Local Responses
 Sympathetic Outflow
 Metabolites
Heart
HR
 contractility
CO
Vessels
Constriction of arterioles
(splanchnic and renal)
Constriction of veins
Dilation of skeletal muscle
arterioles
TPR
Blood flow to all Skeletal Muscle
Blood flow in skeletal muscle during isotonic exercise
40
Blood Flow
100 ml/min
20
0
isotonic exercise
0
10
20
Time (min.)
30
Effect of Exercise on Cardiac Output
•
•
•
•
Heart Rate
•
•
•
•
•
Stroke Volume
•
•
•
•
Cardiac Output
•
•
Watts
0
50
100
150
200
Vo2 max
20

40

60

80

100

Changes in Arterial Blood Pressure-Isotonic Exercise
Systolic BP
Pressure
MAP
Diastolic BP
Rest
Moderate
Severe
Effect of Isotonic Exercise on Arterial Blood Pressure
Blood flow in skeletal muscle during isometric exercise
40
Blood Flow
100 ml/min
20
Isometric Exercise
0
0
10
20
30
Time (min.)
Effect of Isometeric Exercise on Arterial Blood Pressure
Systolic BP
MAP
Pressure
Diastolic BP
Rest
Moderate
Severe
Effect of Isometric Exercise on Arterial Blood Pressure
Effect of Isometric Exercise on Arterial Blood Pressure
Untrained
60
40
Glucagon
20
Trained
0
75%
60%
45%
Level of Exercise
30%
Effects of graded exercise on hormone concentrations showing untrained subjects
and trained subjects.
Effects of Exercise on Growth Hormone
60
40
Untrained
GH
20
0
Trained
75%
60%
45%
Level of Exercise
30%
Effects of graded exercise on hormone concentrations showing untrained subjects
and trained subjects.
Effect of Exercise on Insulin Secretion
20
Untrained
Insulin
10
Trained
0
75%
60%
45%
Level of Exercise
30%
Effects of graded exercise on hormone concentrations showing untrained subjects
and trained subjects.
Effect of exercise on Cortisol, Epinephrine and Norepinephrine
Norepinephrine
Cortisol
Epinephrine
75%
60%
45%
Level of Exercise
30%
Effects of graded exercise on hormone concentrations.