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Respiratory Regulation 
During Exercise
Pulmonary Ventilation
 Respiratory System Anatomy (fig. 
9.1)
 Pulmonary Ventilation
– commonly referred to as breathing
– process of moving air in and out of the 
lungs
– nasal breathing: warms, humidifies, and 
filters the air we breathe
– pleural sacs suspend the lungs from the 
thorax and contain fluid to prevent friction 
against the thoracic cage.
Pulmonary Ventilation
 Inspiration
– is an active process of the diaphragm and 
the external intercostal muscles.
– air rushes in into the lungs to reduce a 
pressure difference.
– forced inspiration is further assisted by 
the scalene, sternocleidomastoid, and 
pectoralis muscles.
 Expiration
– is a passive relaxation of the inspiratory 
muscles and the lung recoils.
– increased thoracic pressure forces air out 
of the lungs
– forced expiration is an active process of 
the internal intercostal muscles 
(latissimus dorsi, quadratus lumborum & 
abdominals).
Pulmonary Diffusion
 Is the gas exchange in the lungs 
and serves two functions:
– it replenishes the blood’s oxygen supply in 
pulmonary capillaries
– it removes carbon dioxide from the 
pulmonary capillaries
 The respiratory membrane (fig. 
9.4)
– gas eschange occurs between the air in the 
alveoli, through the respiratory membrane, 
to the red blood cells in the blood of the 
pulmonary capillaries.
Pulmonary Diffusion
 Partial Pressures of gasses
– the individual pressures from each gas in 
a mixture together create a total pressure.
– air we breathe = 79% (N2), 21% (O2), 
and .03% (CO2) = 760mmHg
– differences in the partial pressures of the 
gases in the alveoli and the gases in the 
blood create a pressure gradient. (fig. 
9.5, 9.6)
Pulmonary Diffusion
 Oxygen’s rate at which it diffuses 
from the alveoli int the blood is 
referred to as the oxygen 
diffusion capacity.
– untrained (45 ml/kg/min) vs trained (80 
ml/kg/min)
due to increased cardiac output, 
alveolar surface area, and reduced 
resistance to diffusion across the 
respiratory membranes.
– large athletes (males) vs small athletes 
(females)
due to increased lung capacity, 
increased alveolar surface area, and 
increased blood pressure from muscle 
pumping.
Pulmonary Diffusion
 Carbon dioxide’s membrane 
solubility is 20 times greater than 
that of oxygen, so CO2 can 
diffuse across the respiratory 
membrane much more rapidly.
Transport of Oxygen By 
The Blood
 Dissolved in the blood plasma 
(2%)
 Dissolved with hemoglobin of red 
blood cells (98%)
– complete hemaglobin saturation at sea 
level is 98%.
– many factors influence hemoglobin 
saturation (fig. 9.7)
 Po2 values (fig. 9.7a)
 decline in pH level from increasing lactate 
levels allows more oxygen to be unloaded and 
higher Po2 is needed to saturate the 
hemaglobin. (fig. 9.7b)
 increased blood temperature allows oxygen to 
unload more efficiently and higher Po2 is 
needed to saturate the hemaglobin. (fig. 9.7c)
 anemia reduces the blood’s oxygen-carrying 
capacity.
Athletes
 Athletes with larger aerobic 
capacities often also have 
greater oxygen diffusion 
capacities due to increased 
cardiac output, blood pressure, 
alveolar surface area, and 
reduced resistance to diffusion 
across respiratory membranes.
Transport of Carbon 
Dioxide in the Blood
 CO2 released from the tissues is 
rarely (7%) dissolved in plasma.
 CO2 combines with H2O, then loses a 
H+ ion to form a bicarbonate ion 
(HCO3) and transports 70% of carbon 
dioxide back to the lungs.
– the lost H+ binds to hemoglobin which 
enhances oxygen unloading
– sodium bicarbonate as an ergogenic aid 
serves the same purpose as a buffer and 
neutralizer of H+ preventing blood 
acidification.
 CO2 can also bind with the amino 
acids of the hemoglobin to form 
carbaminohemoglobin and is 
transported to the lungs. 
Gas Exchange at the 
Muscles
 The arterial-venous oxygen 
difference
(fig. 9.8, 9.9)
– as the rate of oxygen use increases, the 
a-vO2 difference increases.
 Factors influencing oxygen 
delivery and uptake
– under normal conditions hemoglobin is 
98% saturated with O2.
– increased blood flow increases oxygen 
delivery and uptake
because of increased muscle use of 
O2 and CO2 productions
because of increased muscle 
temperature (metabolism)
Gas Exchange at The 
Muscles
 Carbon dioxide exits the cells 
by simple diffusion in response 
to the partial pressure gradient 
between the tissue and the 
capillary blood.
Regulation of 
Pulmonary Ventilation
 Mechanisms of pulmonary 
ventilation (fig. 9.10)
– controlled by respiratory centers of the 
brainstem by sending out periodic 
impulses to the respiratory muscles.
– chemoreceptors also stimulate the brain to 
stimulate the respiratory centers to 
increase respiration to rid the body of 
carbon dioxide. 
– stretch receptors of the pleurae, 
bronchioles and alveoli send impulses to 
the expiratory center to shorten 
inspiration.
– the motor cortex of the voluntary nervous 
system can control ventilation but can also 
be overriden by the involuntary system.
Regulation of 
Pulmonary Ventilation
 The goal of respiration is to 
maintain appropriate levels of 
the blood and tissue gases and 
to maintain proper pH for 
normal cellular function.
 Exercise pulmonary ventilation
(fig. 9.11)
– the anticipatory response creates a pre-
exercise breathing increased depth & 
rate of ventilation.
– gradual exercise ventilation increases 
occur due to temperature and chemical 
status.
– respiratory recovery creates a slow 
decreased ventilation during post-
exercise breathing.
Regulation of 
Pulmonary Ventilation
 Respiratory problems hinder 
performance
– Dyspnea is difficulty or labored 
breathing from poor conditioning of the 
respiratory muscles.
– Hyperventilation is a sudden increase in 
ventilation (mainly expiration) that 
exceeds the metabolic need for oxygen.
pre-exercise hyperventilation creates 
CO2 unloading (swimmers).
Valalva maneuver occurs when air is 
trapped in the lungs which restricts 
venous return, and cardiac output.
Ventilation and Energy 
Metabolism
 Ventilatory Equivalent for 
Oxygen
– is the ratio of volume of air ventilated 
and the amount of oxygen consumed by 
the tissues Ve/Vo2 (fig. 9.12).
– the control systems for breathing keep 
the Ve/Vo2 relatively constant to meet 
the body’s need for oxygen.
 Ventilatory Breakpoint
– is the point at which ventilation 
increases disproportionately to the 
oxygen consumption of the tissues to 
try to clear excess CO2.
– this usually occurs at 55% to 70% of 
Vo2 max and correlates to anaerobic 
threshold and lactate threshold.
Ventilation and Energy 
Metabolism
 Ventilatory Equivalent for 
Carbon Dioxide
– is the ratio of air ventelated to the 
amount of CO2 produced.
– anaerobic threshold is measured by an 
increase in Ve/Vo2 without an increase 
in Ve/Vco2 
(fig. 9.13).
Respiratory Limitations 
to Performance
 Energy produced by oxidation and used by 
the respiratory muscles increases from 2% to 
15% during heavy exercise.
 Pulmonary Ventilation might be a limiting 
factor in highly trained subjects during 
maximal exhaustive exercise due to a high Vo2 
max.
 Airway Resistance and Gas Diffusion in 
the lungs do not limit exercise in a normal 
healthy individual.
 Restrictive or Obstructive Air Ways can 
limit athletic performance by decreasing thePo2 or increasing the Pco2.
– asthma
– bronchitis
– emphasema
Respiratory Regulation 
of 
Acid-Base Balance
 Chemical Buffers
– bicarbonate, phosphates, and proteins
baking soda as an ergogenic aid to 
buffer
– increased ventilation to decrease H+
– accumulated H+ is removed by the 
kidneys and urinary system
– H+ is difussed throughout the body 
fluids and reach equilibrium after only 
5 to 10 minutes of recovery
 this is facilitated by active recovery 
(fig. 9.15).
Static Lung Volumes
 Total Lung Capacity
 Tidal Volume
 Inspiratory Reserve Volume
 Expiratory Reserve Volume
 Residual Lung Volume
 Forced Vital Capacity
 Inspiratory Capacity
 Functional Residual Volume