Metabolic, Cardiovascular, Respiratory Ex. Responses

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Metabolic, Cardiovascular, Respiratory Ex.
Responses
Measuring Oxygen Uptake
Using metabolic system, measure the oxygen
extracted and CO2 produced during exercise
In ambient air O2 20.93 CO2 0.03
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O2/CO2 consumption production
Given Ventilation (VE) is 60 L/min O2 exhaled
16.93 CO2 exhaled 3.03
VO2 60 l/min 4.0 O2 2.4 l/min CO2 60
l/min 3.0 CO2 1.8 l/min
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Fuel Utilization
R Respiratory Quotient cellular level
RER Respiratory exchange ratio measured at
mouth
RER VCO2 / VO2
Fuels used during exercise are mainly glucose and
fat
RER (glucose) 1.0 RER (mixed) 0.85 RER (fat)
0.7
(see page 484)
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Oxygen Uptake Problems
Given VO2 2.3 L/min VCO2 1.8
L/min Calculate RER
Given VE 78 L/min O2 16.67
CO2 4.53 Calculate VO2,
VCO2, RER
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Fuel and Exercise Intensity
Blood glucose and muscle glycogen are CHO fuel
sources
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Fuel and Exercise Duration
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O2 deficit/debt/EPOC
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O2 deficit/debt/EPOC
O2 deficit at onset of exercise due to delay of
cardiovascular system to meet oxygen/ATP
requirement
This energy deficiency is met by CP and glycolysis
O2 debt at end of exercise is better named
Excessive Post-exercise Oxygen Consumption
(EPOC)

• caused by resynthesis of CP stores
• higher heart rate and breathing after exercise
• -conversion of lactate to glucose in liver
• -temperature regulation bring body temp back to
  normal

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Graded Exercise Test (GXT)

• Rationale for GXT
• Clear link between oxygen consumption and
  cardiorespiratory fitness
• GXT is used to evaluate cardiorespiratory
  function
• Monitor cardiovascular variables (ECG, HR, BP),
  respiratory variables (VE, F), and metabolic
  variables (VO2 and HLa).

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Oxygen Uptake and Maximal Aerobic Power

• Oxygen uptake responses to GXT-Fig. 28.11
• VO2 max work increases but VO2 doesnt
• Other criteria in addition to VO2 plateau
• Maximal aerobic power greatest rate at which the
  human body can produce ATP aerobically
• Maximal aerobic power is an indicator of
  cardiorespiratory fitness and decent predictor of
  performance

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Blood Lactic Acid

• Lower work rates, lactate metabolized as fast as
  it is produced - Fig. 28.12
• As stages continue to increase, a point is
  reached at which blood lactate concentration
  suddenly increases Lactate Threshold
• Lactate threshold changes as a result of
  endurance training
• Lactate threshold vs. anaerobic threshold

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Ventilatory threshold
The intensity of work at which the rate of
ventilation sharply increases. Coincides very
closely with lactate threshold Cannot be
explained solely by increased lactate production
McArdles syndrome. Like lactate threshold,
can be changed with training.
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Heart Rate

• Linear increase in HR with work rate in GXT until
  max HR is reached - Figure 28.14
• Variation in max HR among individuals at any age
• Heart rate and oxygen consumption are linear and
  correlated at heart rates of 110 to 150 bpm

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Stroke Volume

• Stroke volume is the amount of blood pumped per
  beat of the heart.
• Stroke volume increases in early stages of GXT
  until about 40 VO2 - Figure 28.15.
• Primary effect of endurance training is increase
  in volume of left ventricle, without change in
  ventricle wall thickness. This increases end
  diastolic volume ? more blood per beat.

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Cardiac Output

• Cardiac output (Q) is volume of blood pumped by
  the heart per minute.
• Cardiac output is calculated by multiplying heart
  rate by stroke volume (page 491)
• Cardiac output increases linearly with work rate
  - Figure 28.16.
• In normal populations, the variable influencing Q
  is SV - Table 28.2

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Cardiac Output Problem
Given HR 60 bpm SV 80 ml/beat
Calculate cardiac output
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Oxygen Extraction

• Oxygen extraction is calculated by subtracting
  the oxygen content of mixed venous blood from the
  oxygen content of arterial blood
• This is called the arteriovenous difference (a-v
  O2 diff)

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Blood Pressure

• Blood pressure is dependent on the balance
  between cardiac output (the faucet) and
  resistance in the blood vessels (the nozzle)
• Systolic blood pressure increases with each
  progressive work load in GXT - Figure 28.18
• Diastolic blood pressure remains steady or
  decreases in a GXT

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Endurance Training Effects

• Increases number of mitochondria and capillaries
  in muscle (increase in IIa and decrease in IIb)
• Decreases time to achieve steady state in
  submaximal exercise

• Increase in volume of ventricle, no change in
  wall thickness
• Maximal aerobic power increases

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Detraining
Observable decline in VO2 max within 7 days
Loss is due to decrease in stroke volume,
which reduces cardiac output
Reduction in plasma volume thought to be main
factor in stroke volume reduction
Sustained periods of detraining will cause
reduction in oxygen extraction
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Maintenance
Maintenance of fitness is more dependent on
the intensity of the exercise rather than the
volume
Reduction of days per week or time per training
session has less effect than reduction in the
intensity of the exercise.
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Cardiovascular Responses to Isometric and
Resistance Exercise

• Heart rate increases progressively in isometric
  exercise - Figure 28.24
• Systolic AND Diastolic blood pressure increase
  progressively in isometric exercise
• Systolic AND Diastolic blood pressure increase
  very high during dynamic, heavy-resistance
  exercise - Figure 28.25
• Valsalva maneuver can cause independent increase
  in blood pressure

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Temperature Regulation

• Body Temperature mechanical efficiency of humans
  ? 20 to 80 energy produced converted to heat
• Homeostasis Heat Gain Heat Loss
• Human body must eliminate heat (4) ways 1.
  Radiation 2. Convection 3.Conduction 4.
  Evaporation - Figures 28.27 28.28

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Heat loss and gain
Radiation heat transfer from surface of one
object to surface of second object without any
contact between the surfaces. Example the sun.
Conduction heat transfer from one object to the
next with contact between surfaces. Example
lying on cold ground.
Convection Special case of conduction. Heat
transferred to air or water, move away from
body, replaced by new molecules. Example fan
or whirlpool.
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Heat loss and gain
Evaporation Conversion from the liquid to the
gaseous state by means of heat. Example sweat.
Sweat evaporation is primary mechanism for heat
loss during exercise.
Sweat loss is dependent upon the gradient of
water vapor pressure between the skin and the
air.
Factors include relative humidity and saturation
pressure.
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Exercise and Heat
Factors to consider are exercise intensity,
temperature and humidity.
More heat will be gained as intensity increases,
core temp will increase. (Fig 28.26)
Adaptations to training in hot and humid
environment Include -increased plasma
volume -earlier sweat onset, higher sweat
volume -reduction in sweat salt loss -reduced
blood flow to skin