Exercise Physiology Chapter 8

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Exercise PhysiologyChapter 8
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Exercise Physiology

• Parent disciplines- biochemistry and biology
• Is the study of the function of the body under
  the stress of acute and chronic physical
  activity.
• Equally concerned with how the body responds to
  the intense demands placed on it by physical
  activity and the changes that occur in the body
  as individuals regularly participate in exercise
  training

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• Neuroedocrine System
• Control of energy balance

• Cardiovascular Respiratory System
• Oxygen and energy delivery
• Internal and external respiration
• Thermoregulation

• Metabolic Systems
• Energy release
• Fuel Reserves

Systems Involved

• Neuromuscular System
• Movement
• Nerve to muscle coordination

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Acute Responses and Chronic Adaptations

• Acute refers to performing a single bout of
  exercise, could be anything from throwing a shot
  put to running a marathon.
• One of the main purposes of exercise physiology
  is to investigate how the body makes internal
  adjustments in the face of the massive
  disruptions in homeostasis that occur with acute
  exercise.
• The technological advances have led to a better
  understanding of the physiology of sports
  performance and of how to better enhance the
  health of the average individual through
  appropriate exercise recommendations

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Acute Responses and Chronic Adaptations

• Chronic refers to a certain length of time over
  which changes take place in different physiologic
  systems during an exercise training program.
• These changes can be interpreted as an
  improvement in the bodys function, both at rest
  and during exercise

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• Exercise Physiologist are interested in studying
  all forms of physical activity
• All physical activity can be placed on a
  continuum.
• Which is useful for classifying exercise in two
  important ways the metabolic and hemodynamic
  responses produced by a given activity

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Metabolic Response

• Ranges from activities that are largely
• Anaerobic
• Aerobic
• Physical activity continuum of metabolic
  responses

Class Power Speed Endurance
Anaerobic
Aerobic
Time 0 3 50
gt120
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Hemodynamic Response

• Refers to the circulation of blood and may also
  encompass the forces restricting or promoting its
  circulation
• Exercises that promote a great deal of blood
  movement involve endurance activities

Class Power Speed Endurance
Pressure Loaded
Volume Loaded
Time 0 3 50
gt120
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Specificity

• Specificity principle states that to maximize
  benefits, training should be carefully matched to
  an athletes specific performance needs or an
  individuals goals.
• Important concept because of the physiological
  adaptations that arise out of an exercise
  training program are highly specific to the
  nature or the training activity

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Who Benefits?

• Everyone one of the major applications of
  exercise physiology is how exercise can be used
  to enhance the quality (if not quantity) of life
  for everyone

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The Science of Exercise Physiology

• The most rudimentary understanding of movement
  can be reduced to the study of biochemical
  processes that release bound or potential energy
  and convert it to free energy.
• Energy can be converted from one form to another
• The conversion of energy takes place according to
  the laws of thermodynamics

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Energy of Movement

• Energy for movement comes from the food we eat,
  which provides energy-rich nutrients in the form
  of carbohydrates, fats, and proteins.
• Foods are broken down into their constituent
  building block molecules which are rich in
  potential energy that is available to be
  converted to free energy
• Energy bound in building block molecules must
  first be converted to another chemical before it
  can become a direct source of energy for muscular
  activity
• Figure 8.5 shows energy nutrient building blocks

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Energy of Movement contd

• The sum of the chemical processes that convert
  energy from indirect sources (the energy
  nutrients) to the source that can be used
  directly to do muscular activity is metabolism.
• Metabolism refers to all of the chemical
  reactions that take place in the body catabolic
  and anabolic processes
• Catabolism is the process of breaking down the
  large energy nutrient molecules to their smaller
  constitute building blocks
• Anabolism is the process whereby smaller
  molecules are built up to larger molecules

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ATP

• For movement to occur catabolic processes are
  linked with anabolic processes for the purpose of
  producing another high energy product -ATP
• Adenosine triphosphate- the direct donor of free
  energy for muscle activity

e- Electron Bonds
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Anaerobic Production of ATP

• Energy produced in the absence of Oxygen
• Power and speed activities are made possible by
  the rapid production of ATP in the cell by means
  of anaerobic metabolic pathways.
• Phosphagen System
• Lactic Acid System

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Phosphagen System

• The ability to rapidly produce ATP is known as
  metabolic power
• Anaerobic pathways produce relatively little ATP
  but the amount they produce is produced rapidly
• The depletion rate of ATP during intense activity
  would be much greater if it were not for Creatine
  Phosphate
• Creatine Phosphate is a high energy phosphate
  that is 3 times as concentrated in muscle than
  ATP, and serves as an important energy reservoir
• When the ATP reservoir is depleted the power
  output of the activity drops off

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Phosphagen System
Energy given off for muscle contraction in power
performances
Creatine phosphate (energy reserve, exhausted in
a few seconds)
Energy for phosphorylation

Creatine
Pi
ATP
Energy for continued power performance is
reformed as ATP
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Lactic Acid System

• During intense activities lasting longer than 10
  seconds (and up to 90 sec), exercising muscles
  rely more and more on glycolysis to pick up where
  the phosphagen system left off
• Glycolysis is the breakdown of glucose
• Involves the use of 11 enzymes (phosphagen only
  needs 2)
• Without glycolysis our high intensity anaerobic
  activities would be limited to our reservoir of
  creatine phosphate (which runs out in only a few
  seconds)
• In Glucose the storage quantity of energy is not
  the limiting factor for intense activity
• Glycolysis is limited or forced to cease before
  glucose is depleted in the cell
• The limitation is brought about by lactic acid
• Lactic acid is a fatiguing substance
• It is formed when glucose is metabolized in
  muscle during intense activity, the last of 11
  reactions
• Gradually it increases in concentration in the
  muscle and spills over into the blood that is
  circulating through the muscle
• The increase of acid build up eventually wears on
  the muscle contractions for 2 reasons
• The build up of the acid in the muscle cell
  causes any further chemical breakdown of glucose
  to be hampered by decreasing the activity of the
  enzymes responsible for glucose breakdown
• As the watery median of the muscle cell becomes
  more acidic, the ability of the muscle to
  continue to contract forcibly is reduced
• The result is that the exercise intensity must be
  reduced

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Lactic Acid System
Glucose Or Glycogen
Slow Glycolysis
ATP
Fast Glycolysis
Pyruvic Acid
Lactic Acid
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Aerobic Production of ATP

• Cellular Respiration- a process that uses oxygen
  to produce ATP
• When the exercise intensity is lower most of the
  energy is liberated by cellular processes that
  are located in specialized cell structures called
  mitochondria
• Cellular respiration involves 5 separate
  metabolic pathways in the breakdown of the 2 main
  energy nutrients (triglycerides and glucose) used
  during endurance exercise
• The break down of triglycerides is termed
  lipolysis and in this process fatty acids are
  released from the triglyceride molecule (this
  primarily takes place in adipose tissue)
• The breakdown of fatty acids is termed
  beta-oxidation, in this process acetyl-CoA
  (acetycoenzyme) is formed.
• The Krebs cycle and electron-transport chain are
  the other pathways involved in the production of
  ATP

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Cellular Respiration
Electrons carried via NADH and FADH
Electrons carried with NADH
Electron Transport Chain and Oxidative
Phosphorylation
Glycolysis
Krebs Cycle
Glucose
Pyruvate
ATP
ATP
ATP
2
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2
Also figure 8.9
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The Cardiorespiratory System

• To meet the demand contracting muscles have for
  oxygen during endurance exercise, major organ
  systems must provide an adequate supply of
  oxygen.
• The function of the pulmonary system is to
  provide a means of gas exchange between the
  external environment and the internal
  environment.
• Part of this function is the process of external
  respiration, whereby oxygen diffuses from the air
  into the lungs and then into the blood
  circulation through the lungs.
• The function of the cardiovascular system is to
  deliver adequate amounts of oxygen and nutrients
  to the body and remove heat and waste.

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The Cardiorespiratory System, cont.

• The integration of the pulmonary and
  cardiovascular system in the delivery,
  extraction, and use of oxygen can be depicted by
  an equation that expresses the relationship
  between three important variables oxygen
  consumption, cardiac output, and the amount of
  oxygen extracted from the blood as it bathes the
  working muscles.
• With endurance exercise, there is an immediate
  need to meet the increased demand for oxygen with
  an adequate supply.
• First, the heart rate and the strength of cardiac
  contractions increase so that the cardiac output
  closely matches any level of oxygen consumption.
• Second, as exercise intensity increases, more
  oxygen is extracted from the blood as the blood
  passes through the capillaries of the working
  muscles.
• Third, the increase in oxygen consumption with
  exercise results from an increase in pulmonary
  ventilation. Pulmonary ventilation in the bulk
  flow of air into and out of the lungs.

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Thermoregulation

• All mammals are homeothermic, which means that we
  must maintain our internal body temperatures
  within narrow limits for survival, regardless of
  the state of the external environment.
• A relatively small part of the energy liberated
  during aerobic exercise is used to perform useful
  work.
• The remaining part of the energy produced is
  stored as heat and must be eliminated to
  maintain our core temperature within reasonable
  levels. If this is not done adequately the
  result may be some form of heat illness or
  possibly even death.
• When aerobic exercise is performed in
  environmental conditions that are favorable (low
  to moderate air temperature and relative
  humidity) the bodys ability to thermoregulate is
  sufficient to keep core temperature increases to
  a minimum.
• Exercising in the heat and humidity results in
  increased cardiovascular stress and reduced
  exercise performance.

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Evaporation

• The ability to adequately dissipate the extra
  heat produced during aerobic exercise depends on
  the evaporative transfer of heat to the
  environment as water is vaporized from the
  respiratory passages and from the surface of the
  skin.
• Evaporation of water (sweat) off the skin is
  especially important because it represents the
  major way heat is removed from the body , during
  exercise, except in hot, humid environments.
• Evaporation is aided when the vapor pressure
  gradient from the skin surface to the air is
  large, which occurs when the relative humidity of
  the air is low.
• Exercising in conditions of low relative humidity
  is , therefore, desirable.

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Water intake

• One of the most important things that one can do
  when exercising in a hot environment is to drink
  plenty of water.
• Studies have shown that water replacement is
  effective in keeping to a minimum the increase in
  core temperature that occurs with exercise.
• Those who drink too much or too little water
  while exercising experienced a significantly
  greater body core temperature.

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Muscle Fiber Types A determinant of sport
performance

• With the advent of the needle biopsy technique to
  sample human skeletal muscle fibers before,
  during, and after exercise, exercise physiology
  research has been able to establish a link
  between muscle fiber types and sports
  performance.
• The main muscle fibers that have been
  characterized are slow oxidative, fast oxidative
  glycolytic, and fast glycolytic.

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Muscle Fiber Types A determinant of sport
performance

• Fast glycolytic fibers have a much higher
  capacity to breakdown glucose to lactic acid.
• Slow oxidative fiber has a much higher capacity
  to use oxygen in the aerobic breakdown of energy
  nutrients.
• Fast oxidative glycolytic muscle is also referred
  to as intermediate, because it has a slightly
  greater oxidative capacity and slightly lower
  glycolytic capacity than the fast glycolytic
  fiber, which makes it the true anaerobic fiber
• The metabolic and contractile properties of these
  fibers can influence exercise performance.

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Overtraining Is more really better??

• Athletes often want more of a physiologic return
  for their training time. To do this they often
  fall prey to the old saying that More is
  better.
• There is a fine line between optimal training and
  overtraining for both the athlete and nonathlete.
• When that line is crossed, decrements in
  performance capacity will occur along with myriad
  other problems, some medical and physiologic and
  others psychological (see box 8.7).
• The problem of overtraining has been the focus of
  a substantial amount of research aimed at
  increasing our understanding of the physiologic,
  pathophysiologic, nutritional, immunologic, and
  psychological consequences of overtraining in
  endurance and strength and power athletes.

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Overtraining Is more really better??

• The overtraining condition is more than just an
  acute problem that can be alleviated with
  short-term rest.
• It is also more than a slight decrease in
  competition-level performance capability.
• Rather the problem is chronic and cannot be
  easily remedied.