Download Physio Chap 84 [10-26

Physio Chapter 84
Thursday, January 17, 2013
10:32 PM
Sports Physiology
 Female and Male Athletes
o Most of the difference total muscle performance between males and females is from the
extra muscle in men.
o Testosterone secreted by male testes has a powerful anabolic effect which causes increased
protein deposition, especially in muscle.
 Muscles in Exercise
o Strength, Power, and Endurance of Muscles
 Strength of a muscle comes mainly from size; Maximal Contractile Force 3-4 kg/cm^3
of cross-sectional area.
 Holding strength of muscles is about 40 percent greater than the contractile strength.
 Forceful stretching of a maximally contracted muscle is one of the best ways to get
huge amounts of soreness.
 Power is a measure of the total amount of work that the muscle performs in a unit
period of time.
 So power comes not only from strength but from the distance of contraction
and the number of times it contracts per minute.
 A person has the capability of extreme power surges for short periods of time,
whereas for long-term endurance events, the power output of the muscles is only one
fourth as great as during the initial power surge.
 This does not mean that performance is four times as great in the beginning, it
means that the efficiency for change of muscle power output into athletic
performance is often much less during rapid activity than during less rapid but
sustained activity.
 Endurance depends on the nutritive support for the muscle - more than anything else
on the amount of glycogen that has been stored in the muscle before the period of
exercise. High-carb diets are better for storing up for exercise!
Muscle
Metabolic
Systems of Exercise
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o ATP is used for energy because the two phosphate bonds on the end give out 7300 calories
of energy each.
 The amount of ATP present in muscles is enough for 3 seconds of maximum muscle
power. Not enough!
o Phosphocreatine-Creatine System
 The high energy phosphate bond of phoshocreatine has more energy than the bond of
ATP, 10,300 calories!
 Transfer of energy from phosphocreatine to ATP is very fast so it is almost
instantaneously available.
 Muscle cells have two to four times the amount of ATP stored in
phosphocreatine.
 The combine Phosphocreatine and ATP are called the Phosphagen Energy System and
they can provide about 8-10 seconds of maximum muscle power.
 Used for short bursts of maximal muscle power.
o Glycogen-Lactic Acid System
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Glycogen is split into glucose and glucose is used for energy through glycolysis.
Gylcolysis is anerobic and breaks down glucose into two pyruvate molecules for FOUR
ATP molecules.
 The pyruvate becomes lactic acid because of the lack of oxygen for oxidative
phosphorylation.
 Forms ATP 2.5 times faster than oxidative mechanism of mitochondria.
 Provides 1.3-1.6 minutes of maximal muscle power in addition to the 8-10 seconds of
the Phosphagen Energy System, although at somewhat LESS power.
Aerobic System
 Oxidation in mitochondria for ATP production = very slow but lasts for as long as the
nutrients last.
 The Phosphagen system is used by the muscle for power surges of a few seconds and
the aerobic system is for prolonged activity.
Recovery of Metabolic Systems
 Energy from Glycogen-Lactic Acid system can replenish ATP for Phosphagen System
and also aerobic sytesm can replenish ATP for the two below it.
 Reconstitution of the lactic acid system means mainly the removal of excess lactic acid
that has accumulated because it causes extreme fatigue.
 Small portion is converted to pyruvic acid and used for energy
 The rest is reconverted to glucose mainly in the liver.
Recovery of the Aerobic System
 Two effects of depleted energy capability
 Oxygen Debt:
 In heavy exercise, almost all of the body's stored oxygen is used within a
minute or so for aerobic metabolism. After the exercise is done, the
stored oxygen must be replenished by breathing extra amounts of oxygen
over and above the normal requirements. All this extra oxygen must be
"repaid" to the body.
 Even after the exercise is over, the oxygen uptake is above normal, at first
very high to resonstitute the phosphagen system and repaying the stored
oxygen portion of the oxygen debt, and then for another 40 minutes at a
lower level while the lactic acid is removed.
 Early portion of oxygen debt is called the alactacid oxygen debt equaling
about 3.5 liters and the latter portion is called the lactic acid oxygen debt
and equals about 8 liters.
 Depletion of the Glycogen Stores:
 Recovery often takes days.
 On high-carb diets, recovery takes about 2 days while people on high-fat,
high-protein diets show little recovery even after as long as five days.
Nutrients Used During Muscle Activity
 As well as carbs, muscles use large amounts of fat for energy in the form of fatty acids
and acetoacetic acid and to a much less extent in the form of amino acids from
proteins.
 Most of the energy comes from carbs during first few seconds or minutes, but at the
time of exhaustion, 60-85% of energy comes from fats.
 Glycogen and blood glucose are nutrients of choice for intense muscle activity but for
long-term endurance, fats supply more than 50% of the required energy after the first
3-4 hours.
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Effect of Athletic Training on Muscles and Muscle Performance
 Resistance Training
 Muscles that function under no load, even if they are exercised for hours on
end, increase little in strength.
 Muscles that contract at more than 50% maximal force of contraction will
develop strength rapidly even if contractions are performed only a few
times each day.
 Hypertrophy
 Changes inside hypertrophied muscles include
 Increase number of myofibrils
 Up to 120% increase in mitochondrial enzymes
 As much as 60-80% increase in components of the Phosphagen System,
including ATP and Phosphocreatine
 As much as 50% increase in stored glycogen
 As much as 75-100% increase in stored triglycerides.
 Fast Twitch vs Slow Twictch Fibers
 Basic differences
 Fast twitch are about twice as large
 Enzymes that release energy from Phosphagen and Glycogen-Lactic Acid
systems are two to three times as active in fast twitch, thus making the
max power that can be achieved for very short periods of time by fast
twitch fibers about twice as great as that of slow twitch fibers.
 Slow twitch are for endurance and have more mitochondria and
myoglobin which increases the rate of diffusion of oxygen throughout the
fiber by shuttling oxygen from one myoglobin to the next. They also have
more enzymes for aerobic metabolism than fast twitch fibers.
 The number of capillaries is greater in the vicinity of slow twitch fibers.
 Hereditary Differences for Fast and Slow twitch fibers
 Genetics plays a huge part in the proportion of fast vs slow twitch. Athletic
training has not been shown to change this.
Respiration in Exercise
o Oxygen Consumption and Pulmonary Ventilation in Exercise
 Both oxygen consumption and total pulmonary ventilation increase about 20-fold
between the resting state and maximal intensity of exercise in the well-trained
athlete. Linear correlation.
o Limits of Pulmonary Ventilation
 Maximal breathing capacity is about 50% greater than the actual pulmonary
ventilation during maximal exercise
 This gives a safety cushion for athletes to call on during exercise at high
altitudes, during hot conditions, and with abnormalities in the respiratory
system.
 The ability of the heart to pump blood to the muscles is usually a greater limiting
factor in the delivery of oxygen to the muscles.
o Effect of Training on VO2 max
 In the study, VO2 Max only increased about 10% and whether the frequency of
training was two or five times a week, little change was recorded.
 Part of greater VO2 Max is greater chest sizes and stronger respiratory muscles, partly
due to genetics.
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Oxygen Diffusing Capacity of Athletes
 Measure of the rate at which oxygen can diffuse from the alveoli into the blood
expressed in terms of milliliters of oxygen that will diffuse each minute for each
millimeter of mercury difference between alveolar partial pressure of oxygen and
pulmonary blood oxygen pressure.
 Huge difference in diffusing capacity between rest and exercise because blood flow
through many pulmonary capillaries is sluggish or dormant in the resting state, while
in exercise, increased blood flow through the lungs causes all the capillaries to be
perfused at max rates, which provides greater surface area for oxygen to diffuse
through.
o Blood Gases During Exercise
 Remain nearly normal due to the ability of the respiratory system to provide adequate
aeration of the blood even during exercise.
 Respiration is stimulated mainly by neurogenic mechanisms during exercise.
o Effect of Smoking on Pulmonary Ventilation in Exercise
 Reasons for decreased wind
 Nicotine constricts terminal bronchioles, which increases resistance of airflow
both in and out.
 Irritating effects of smoke cause increased fluid secretion into the bronchial tree
as well as swelling of the epithelial linings
3. Nicotine paralyzes the cilia that normally remove excess fluids and foreign
particles; debris accumulates and add difficulty to breathing.
 Effects of Chronic Smoking
 Chronic bronchitis
 Obtruction of many terminal bronchioles
 Destruction of alveolar walls, as much as 4/5 the respiratory membrane.
Cardiovascular System in Exercise
o Muscle Blood Flow
 Drastic increases in blood flow during exercise
 As much as 25-fold increase.
 Almost one half of this increase caused by increased muscle metabolism.
 The rest if from several factors, the most important being increased arterial
blood pressure due to exercise.
 Usually about 30% which can more than double the flow itself.
 Contraction of muscle decreases blood flow because it compresses the blood vessels
 Tonic muscle contraction can cause rapid muscle fatigue because of lack of
delivery of oxygen and nutrients.
o Effect of Training on Hypertrophy and on Cardiac Output
 Marathon runners can get CO 40% above untrained persons due to 40% enlargement
of heart chambers and 40% increase in heart mass.
 Resting CO in marathonners is about the same as untrained, even though their hearts
are bigger. This is due to a large stroke volume at a reduced heart rate.
 The heart-pumping effectiveness of each heart beat is 40-50% greater in the
highly trained athlete than in the untrained person, but there is a corresponding
decrease in heart rate at rest.
o Relation of Cardiovascular Performance to VO2 Max
 During max exercise, both heart rate and stroke volume are increased to about 95% of
max.
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Cardiac output is equal to heart rate x stroke volume so CO is about 90% of maximum
that someone can achieve.
 At 90% max CO, pulmonary ventilation is at 65% max so CO reaches its' maximum first
and is the limiting factor in VO2 Max.
o Effect of Heart Disease and Old Age on Athletic Performance
 Any type of heart disease that reduces max CO will cause an almost corresponding
decrease in achievable total body muscle power.
 Max CO of older people also decreases as much as 50% between 18 and 80 years.
Body Heat in Exercise
o Max efficiency for conversion of nutrient energy into muscle work is only 20-25%.
o Almost all every that goes into muscle work becomes body heat because only a small
portion is used for overcoming viscous resistance to movement of muscles and joints and
overcoming the friction of blood flowing through the blood vessels.
o Heatstroke
 On hot and humid days, body temp can reach up to 106-108 degrees F. At this level,
the temp becomes destructive to tissue cells, especially brain cells. This induces
 Extreme weakness
 Headache
 Dizziness
 Nausea
 Profuse sweating
 Confusion
 Staggering gate
 Collapse
 Unconsciousness
 At these high temps, the temp-regulating mechanism often fails and the high temp
also increases the rate of intracellular chemical reactions which liberates more heat.
No bueno.
 Treatment is to reduce body temp as fast as possible.
Body Fluids and Salt in Exercise
o By progressively exercising in heat, your sweat glands become acclimatized so you lose small
amounts of salt.
 This results mainly from increased aldosterone secretion by the adrenal cortex.
 Aldosterone increases reabsorption of sodium chloride from the sweat before it is
released onto the skin.
Drugs and Athletes
o Caffeine: no concrete results that it helps with performance
o Anabolic Steroids (or androgens): increase muscle strength but greatly increase risk of
cardiovascular damage because they often cause hypertension, decrease HDL, and
increased LDL
 Leads to decreased testicular function, including decreased formation of sperm and
decrease secretion of natural testosterone.
o Amphetamines and Cocaine
 Only proven as a psychic stimulant.
 Possible cause of death may be overexcitability of the heart, leading to ventricular
fibrillation, which is lethal within seconds.
Body Fitness Prolongs Life
o Studies have shown mortality to be three times less in fit people vs non-fit people.
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Body fitness and weight control greatly reduce CVD.
 Results from maintenance of lower blood pressure and reduced blood cholesterol
and LDLs with increased HDLs.
Fit people have more bodily reserves to call on when he or she does become sick.