Download Chapter_05

Exercise Physiology
Chapter 5
Copyright © 2014 American College of Sports Medicine
Objectives
• Provide fundamental background about the biological
function of the human body
• Introduce the physiological mechanism of various
systems of the body and how they relate to exercise
training
• Identify key elements that the body reacts to and adapts
to exercise stimulus so that effective exercise training
can be prescribed
Copyright © 2014 American College of Sports Medicine
Overview of exercise physiology
• Effect of exercise on various body systems
• Interaction of body systems
• Nature of exercise stimulus given to body
• Knowledge of energy metabolism
• Rapid advances in technology and research
Copyright © 2014 American College of Sports Medicine
What is “exercise physiology”?
• The study of the body’s responses and its
adaptations to the stress of exercise
– Immediate (acute) effects
– Long-term (chronic) effects
• Systems interact to respond to exercise demands
Copyright © 2014 American College of Sports Medicine
Cardiovascular system
• Heart and blood vessels:
– Closed circuit
– Deliver nutrients to and remove metabolic
wastes from tissues
– Assist maintenance of normal function at rest
and during exercise
Copyright © 2014 American College of Sports Medicine
Cardiovascular system (cont.)
1. Transports deoxygenated blood from the heart to
the lungs and oxygenated blood from the lungs to
the heart
2. Transports oxygenated blood from the heart to
tissues and deoxygenated blood from the tissues to
the heart
3. Distributes nutrients (e.g., glucose, free fatty acids,
amino acids) to cells
Copyright © 2014 American College of Sports Medicine
Cardiovascular system (cont.)
4. Removes metabolic wastes (e.g., carbon dioxide,
urea, lactate) from the periphery for elimination or
reuse
5. Regulates pH to control acidosis and alkalosis
6. Transports hormones and enzymes to regulate
physiological function
7. Maintains fluid balance to prevent dehydration
8. Maintains body temperature by absorbing and
redistributing heat
Copyright © 2014 American College of Sports Medicine
Figure 5.1. Anatomy of the heart and direction of blood flow. From Smeltzer SCO, Bare BG. Brunner and
Suddarth's Textbook of Medical–Surgical Nursing. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins;
2002, with permission.
Copyright © 2014 American College of Sports Medicine
Tissue coverings and layers of the
heart
• Pericardium: membranous sac that covers the heart:
– Fibrous (tough) layer
– Serous (smooth) layer
• Epicardium: interior lining of heart
• Myocardium is cardiac muscle:
– Thickest layer of heart tissue
– Connective tissue fibers (fibrous skeleton) supports
myocardium and valves
Copyright © 2014 American College of Sports Medicine
Chambers and valves of the heart
• Chambers:
– Right atria and right ventricle (RV)
– Left atria and left ventricle (LV)
• Valves:
– Atrioventricular (AV) valves—tricuspid and
mitral (bicuspid)
– Semilunar valves—pulmonic and aortic
Copyright © 2014 American College of Sports Medicine
Blood flow and conduction system of
the heart
• Blood flow:
– Pulmonary circuit
– Systemic circuit
• Conduction system
Copyright © 2014 American College of Sports Medicine
The blood vessels
• Deliver blood to tissues
• Promote exchange of nutrients, metabolic
wastes, hormones, other substances with cells
• Return blood to heart
• Closed system:
– Arteries
– Arterioles
– Capillaries
– Venules
– Veins
Copyright © 2014 American College of Sports Medicine
Cardiac function: heart rate
• Heart rate (HR) = beats per minute (bpm)
• Average is 60 to 80 bpm
• Typically higher in women than in men
• Higher in children than adults
• Lower in the elderly
• Lower in fit individuals
Copyright © 2014 American College of Sports Medicine
Cardiac function: blood pressure
• Systolic pressure (SBP): pressure exerted on
arterial wall during contraction:
– Average is 120 mm Hg
• Diastolic pressure (DBP): pressure during relaxation
phase of ventricles:
– Average is 80 mm Hg
• SBP exceeding 140 mm Hg or DBP exceeding 90
mm Hg may indicate hypertension
Copyright © 2014 American College of Sports Medicine
Cardiac function: stroke volume
• Stroke volume (SV): amount of blood ejected from
left ventricle in a single contraction
• End-diastolic volume (EDV): total volume of blood
in ventricles at end of diastole
• End-systolic volume (ESV): total volume of blood in
ventricles at end of systole
• SV = difference between EDV and ESV
Copyright © 2014 American College of Sports Medicine
Cardiac function: cardiac output
.
• Cardiac output (Q)—volume of blood pumped by the
heart per minute
.
• Q = HR  SV
• Sensitive to body position
Copyright © 2014 American College of Sports Medicine
Acute responses to cardiovascular
exercise
• Mechanisms function collectively to support
increased aerobic requirements of physical activity
• As exercise intensity increases, oxygen
consumption and carbon dioxide production by
working muscles increase
• The cardiorespiratory system attempts to maintain
cellular homeostasis
• The central nervous system increases neural
ventilatory and cardiac drive
Copyright © 2014 American College of Sports Medicine
Acute responses: heart rate
• Heart rate (HR) increases linearly with work rate
and oxygen uptake during dynamic exercise.
• Maximum attainable HR decreases with age at
approximately HR = 220 – age
Copyright © 2014 American College of Sports Medicine
Acute responses: stroke volume
• SV increases curvilinearly with work rate until
reaching near-maximal level
• Maximal level = approximately 40% to 50% of
aerobic capacity
• At maximum SV, increase in oxygen demand is met
by increasing HR
Copyright © 2014 American College of Sports Medicine
Acute responses: cardiac output
.
• Q increases linearly with work rate
.
• Maximum Q depends on many factors:
– Age
– Posture
– Body size
– Presence of cardiovascular disease
– Physical conditioning level
.
• Increases in Q are facilitated by increases in HR and SV
Copyright © 2014 American College of Sports Medicine
Acute responses: arteriovenous
oxygen difference (a-vO2 Difference)
• Oxygen extraction of tissues at rest:
– Use coefficient approximately 25%
– 5 mL O2·dL–1
• Oxygen extraction of tissues during exercise to
exhaustion:
– Use coefficient approximately 75%
– 15 mL O2·dL–1
Copyright © 2014 American College of Sports Medicine
Acute responses: blood flow
.
• At rest, 15% to 20% of Q is distributed to skeletal muscles
.
• During exercise, 85% to 90% of Q is distributed to skeletal
muscles
• Myocardial blood flow increases
• Blood supply to brain maintained at resting levels
Copyright © 2014 American College of Sports Medicine
Acute responses: blood pressure
• SBP increases linearly with exercise
• Maximal values are typically 190 to 220 mm Hg
• Terminate exercise testing in persons with a
decreasing SBP
Copyright © 2014 American College of Sports Medicine
Acute responses: maximal oxygen
consumption
.
• VO2max (aerobic capacity) is measure of cardiopulmonary
fitness
• Measured in liters per minute
.
.
• Relative V O2max = VO2max divided by body weight in kilograms
Copyright © 2014 American College of Sports Medicine
Respiratory system
• Consists of nose, nasal cavity, pharynx, larynx,
trachea, bronchial tree, and lungs
• Filters air
• Allows for gas exchange within lungs
Copyright © 2014 American College of Sports Medicine
Figure 5.2. The structures of the respiratory
system (anterior view). From Stedman's Medical
Dictionary. 27th ed. Baltimore, MD: Lippincott
Williams & Wilkins; 2000, with permission.
Copyright © 2014 American College of Sports Medicine
Control of breathing
• Breathing control results from interplay of
brainstem and other respiratory pathways:
– Brainstem: autonomic control structures
– Cerebral cortex: voluntary control structures
Copyright © 2014 American College of Sports Medicine
Distribution of ventilation
• Ventilation of pulmonary system is accomplished in
two major divisions:
– Upper respiratory tract
– Lower respiratory tract
Copyright © 2014 American College of Sports Medicine
Upper respiratory tract
• Conduction pathway for air into lower respiratory
tract
• Purifies and humidifies air before it reaches gas
exchange units
• Nose
• Sinuses
• Pharynx
• Larynx
Copyright © 2014 American College of Sports Medicine
Lower respiratory tract
• 23 generations (divisions) of airways
• Trachea
• Bronchi
• Bronchioles
• Alveoli
Copyright © 2014 American College of Sports Medicine
Ventilatory pump
• Chest wall
• Respiratory muscles
• Pleural space
Copyright © 2014 American College of Sports Medicine
Ventilatory pump: chest wall
• Primary intercostal muscles
• Bones:
– Spine
– Ribs
– Sternum
• Inspiration: more negative pressure in pleural
space and lungs than in atmosphere
• Expiration: positive pressure generated by elastic
recoil of lungs
Copyright © 2014 American College of Sports Medicine
Ventilatory pump: respiratory muscles
• Only skeletal muscles essential to life
• Diaphragm
• Internal and external intercostals
• Abdominal muscles
Copyright © 2014 American College of Sports Medicine
Figure 5.3. Mechanics of normal — not deep, not shallow — inspiration (left) and expiration (right). From
Weber J, Kelley J. Health Assessment in Nursing. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins;
2003, with permission.
Copyright © 2014 American College of Sports Medicine
Ventilatory pump: pleura
• Visceral (inner layer) pleura
• Plural space
• Parietal (outer layer) pleura
Copyright © 2014 American College of Sports Medicine
Distribution of blood flow
• Pulmonary arteries supply blood to lungs:
– Pulmonary circulation normal mean pressure
approximately 15 mm Hg
• Bronchial arteries supply blood to bronchi and
bronchioles
• Gas exchange occurs in walls of alveoli
Copyright © 2014 American College of Sports Medicine
Pulmonary ventilation
.
• Pulmonary ventilation (VE):
– Volume of air exchanged per minute,
approximately 6 L·min–1
– Can increase 15- to 25-fold at maximal exercise
– Perhaps regulated more by requirement for
carbon dioxide removal
Copyright © 2014 American College of Sports Medicine
Ventilatory changes
• Adaptations that result from physical conditioning:
– Larger lung volume and diffusion capacity
– Maximal ventilatory capacity may increase
– Submaximal ventilation may decrease
Copyright © 2014 American College of Sports Medicine
Energy systems
• Food is metabolized to produce energy
• Anaerobic metabolism (anaerobic glycolysis)
• Aerobic metabolism (oxidative phosphorylation)
Copyright © 2014 American College of Sports Medicine
Figure 5.4. Comparison of activity with the energy pathways used (ATP = adenosine triphosphate, PCr =
creatine phosphate, ATP + PCr + lactic acid = anaerobic glycolysis, electron transport-oxidative
phosphorylation = aerobic oxidation). From Premkumar K. The Massage Connection, Anatomy and
Physiology. 2nd ed. Baltimore, MD: Lippincott Williams & Wilkins; 2004, with permission.
Copyright © 2014 American College of Sports Medicine
Metabolism
• Available stores of ATP are limited (several seconds
worth of activity)
• Energy production relies heavily on respiratory and
cardiovascular systems:
– Oxygen and nutrient delivery
– Removal of waste products
Copyright © 2014 American College of Sports Medicine
Adenosine triphosphate (ATP)
• Energy is released through hydrolysis of ATP.
• Hydrolysis forms adenosine diphosphate (ADP) and
inorganic phosphate (Pi).
• ATPase enzyme is the catalyst.
ATP
(ATPase)
ADP + Pi + energy
Copyright © 2014 American College of Sports Medicine
Creatine phosphate (CP)
• The CP system transfers high-energy phosphate
from CP to rephosphorylate ATP from ADP.
• Creatine kinase is the catalyst.
• Rapid system: one enzymatic step.
• Anaerobic system
• A limited amount of ATP is produced.
ADP + CP
(creatine kinase)
ATP + C
Copyright © 2014 American College of Sports Medicine
Anaerobic glycolysis
• Carbohydrate (glycogen or glucose) degrades to
pyruvate or lactate
• Series of enzymatically catalyzed steps
• Does not use oxygen
• Can participate in aerobic production of ATP
Copyright © 2014 American College of Sports Medicine
Figure 5.5. A net yield of 32 ATPs from energy
transfer during the complete oxidation of one
glucose molecule in glycolysis, the citric acid cycle,
and electronic transport. From Katch VL, McArdle
WD, Katch FI. Essentials of Exercise Physiology. 4th
ed. Baltimore, MD: Lippincott Williams & Wilkins;
2011, with permission.
Copyright © 2014 American College of Sports Medicine
Aerobic oxidation
• Oxidative phosphorylation can use fat, protein, and
carbohydrate to produce ATP
• Krebs cycle (citric acid cycle)
• As duration and intensity of activity increases,
aerobic energy metabolism increases
Copyright © 2014 American College of Sports Medicine
Initial responses to exercise
• Oxygen deficit is the lag in oxygen consumption at the
beginning of exercise
• Describes the difference between the required oxygen
necessary for meeting the energy demand of exercise
and the actual oxygen consumption
Copyright © 2014 American College of Sports Medicine
Recovery from exercise
• Excess postexercise oxygen consumption (EPOC)
remains elevated for several minutes during
recovery from exercise.
• EPOC remains elevated longer after prolonged
exercise than shorter-term exertion.
Copyright © 2014 American College of Sports Medicine
Muscular system
• All movements require muscular action
• There are three major muscle types:
– Skeletal (striated)—voluntary
– Smooth (forms internal organs)—involuntary
– Cardiac (heart muscle)—involuntary
Copyright © 2014 American College of Sports Medicine
Skeletal muscles
• Muscle bundles—fasciculi:
– Covered and separated by perimysium
• Individual muscle fibers:
– Endomysium
– Sarcolemma—membrane that encloses cell
contents
Copyright © 2014 American College of Sports Medicine
Figure 5.6. Structure of skeletal muscle. Asset
provided by Anatomical Chart Co.
Copyright © 2014 American College of Sports Medicine
Muscle contraction
• Sarcomere—smallest contractile unit of muscle:
– Actin (thin filament)—troponin and tropomyosin
– Myosin (thick filament)—cross bridges
• Sliding filament theory
• All-or-none principle
Copyright © 2014 American College of Sports Medicine
Figure 5.7. The sliding-filament model (contraction of skeletal muscle results from the sliding of the actin
chains on the myosin chains). From Oatis, Carol A. Kinesiology — The Mechanics and Pathomechanics of
Human Movement. Baltimore, MD: Lippincott Williams & Wilkins; 2004.
Copyright © 2014 American College of Sports Medicine
Muscle contraction (cont.)
• Static (isometric):
– Muscle group maintains constant length
– No change in joint position
Copyright © 2014 American College of Sports Medicine
Muscle contraction (cont.)
• Dynamic (isotonic):
– Movement of joint
– Muscle shortens (concentric contraction)
– Muscle lengthens (eccentric contraction)—
greater force production
• Isokinetic:
– Constant-speed muscular contraction against
accommodating resistance
Copyright © 2014 American College of Sports Medicine
Muscle fiber types
• Different fiber types not mutually exclusive
• Question as to whether training can change muscle
types
Copyright © 2014 American College of Sports Medicine
Type I muscle fibers
• Low-intensity, long-duration activities
• Slow twitch
• Aerobic
Copyright © 2014 American College of Sports Medicine
Type II muscle fibers
• Force generation
• IIA—transition between type I and type II fibers
• IIB—Shorten and develop tension faster than type I
fibers
Copyright © 2014 American College of Sports Medicine
Neuromuscular activation
• Stimulus for voluntary muscle activation:
– Brain
– Brainstem
– Spinal cord
– Specific motor unit activation pattern
Copyright © 2014 American College of Sports Medicine
Motor unit activation
• Motor unit:
– Motor neuron
– Muscle fibers innervated by motor neuron
• Heavy resistance training affects motor unit firing
rates and/or frequencies
Copyright © 2014 American College of Sports Medicine
Skeletal system
• Axial skeleton
• Appendicular skeleton
Copyright © 2014 American College of Sports Medicine
Structure and function of joints
• Joints—articulations between bones:
– Fibrous
– Cartilaginous
– Synovial
• Ligaments—connect bone to bone
Copyright © 2014 American College of Sports Medicine
Structure and function of joints (cont.)
• Tendons—connect muscle to bone
• Proprioception
• Joint movement:
– Active range of motion (AROM)
– Passive range of motion (PROM)
Copyright © 2014 American College of Sports Medicine
Neurological system
• Central nervous system (CNS):
– Brain
– Spinal cord
• Peripheral nervous system (PNS):
– Peripheral nerves of voluntary system
Copyright © 2014 American College of Sports Medicine
Figure 5.8. Basic organization of the nervous
system. The brain and spinal cord constitute the
CNS. A collection of nerve cell bodies in the CNS is a
nucleus, and a bundle of nerve fibers connecting
neighboring or distant nuclei in the CNS is a tract.
The PNS consists of nerve fibers and cell bodies
outside the CNS. Peripheral nerves are either cranial
or spinal nerves. A collection of nerve cell bodies
outside the CNS is a ganglion (e.g., a cranial or
spinal ganglion). From Moore KL, Dalley AF II.
Clinical Oriented Anatomy. 4th ed. Baltimore, MD:
Lippincott Williams & Wilkins; 1999.
Copyright © 2014 American College of Sports Medicine
Central nervous system
• Body’s central control center
• Brain:
– Protected by bony skull
• Spinal column:
– Extension of the brain
– Surrounded and protected by vertebral column
Copyright © 2014 American College of Sports Medicine
Peripheral nervous system
• Cranial nerves associated with brain
• Spinal nerves associated with spinal cord
• Ganglia—groups of nerve cell bodies
Copyright © 2014 American College of Sports Medicine
Peripheral nervous system (cont.)
• Two nerve fiber types:
– Afferent (sensory)
– Efferent (motor)
• Branches of PNS:
– Somatic nervous system
– Visceral nervous system (autonomic nervous
system)
Copyright © 2014 American College of Sports Medicine
Autonomic nervous system
• Two pathways:
– Sympathetic—under stressful (alarm)
conditions
– Parasympathetic—conserves and restores body
resources
Copyright © 2014 American College of Sports Medicine
Neuromuscular control
• Sensory stimulation
• Motor command released
• Nerve pulse transmitted to targeted muscle
• Motor unit activation—proceeds from type I to type
IIa to type IIb
• Proprioceptors—sensitive to stretch, tension, and
pressure
Copyright © 2014 American College of Sports Medicine
Muscle spindle and golgi tendon organs
• Muscular contraction is affected by specialized sensory
receptors in the muscles and tendons that are sensitive to
stretch, tension, and pressure.
• These receptors are termed proprioceptors.
• A sensory receptor called a muscle spindle is sensitive to the
stretch of a muscle and is embedded within the muscle fiber.
• Golgi tendon organs are another type of specialized
proprioceptor that attach to the tendons near the junction of
the muscle.
• These receptors detect differences in the tension generated by
active muscle rather than muscle length.
Copyright © 2014 American College of Sports Medicine
Figure 5.9. Structure of the Golgi tendon organ.
From Premkumar K. The Massage Connection,
Anatomy and Physiology. 2nd ed. Baltimore, MD:
Lippincott Williams & Wilkins; 2004.
Copyright © 2014 American College of Sports Medicine
Exercise adaptations: resistance
training
• Overload principle
• Improved aerobic enzyme systems
• Nervous system changes
Copyright © 2014 American College of Sports Medicine
Exercise adaptations: cardiovascular
exercise training
• Increased functional capacity in clients with
coronary artery disease (CAD)
• Increased aerobic capacity
• Reduced heart rate and systolic blood pressure at
rest
• Decreased lactic acid production and muscle blood
flow
Copyright © 2014 American College of Sports Medicine
Exercise adaptations: cardiovascular
exercise training (cont.)
• Resting heart rate decreases
• Stroke volume increases at rest and during exercise
.
• Q will increase during exercise
• a-vO2 difference increases
• Resting SBP and DBP may decrease
• Less lactic acid produced at submaximal workloads
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine
Exercise adaptations: cardiovascular
exercise training and sex-specific
improvement
• Women respond in much the same way as men to exercise
programs.
• Improvement is negatively correlated with age, habitual
physical activity, initial VO2max.
• Improvement is positively correlated with conditioning
frequency, intensity, and duration.
Copyright © 2014 American College of Sports Medicine
Copyright © 2014 American College of Sports Medicine