Chapter 3
Cardiorespiratory Endurance
• The ability of the body to perform prolonged, large
muscle, dynamic exercise at moderate-to-high levels of
• This is the most important health related component of
physical fitness.
• A healthy heart is essential to high levels of fitness and
wellness, as well as to a long and healthy life!
The Heart
~ A very muscular organ
~ Four chambered, fist-sized muscle.
~ Weighs between 8 and 10 oz.
~ Lies slightly to the left of center in the chest.
~ Each day, will beat 100,000 times (at rest).
~ Purpose is to pump oxygen-poor blood
to the lungs, and oxygen-rich blood
to the rest of the body.
~ At rest, about 5 qts. of blood are
circulated each minute.
~ With exercise about 20 or more
qts. of blood are pumped out
per minute.
Cardiorespiratory System
• The CR system consists of the heart, blood
vessels, and the respiratory system.
• The CR system picks up and transports oxygen,
nutrients, and other substances to the organs and
tissues that need them.
• The CR system then picks up waste products and
carries them to where they are expelled.
• Cardio means “heart”
• Respiratory means “lungs”
Cardiorespiratory System
Cardiorespiratory System
• Blood vessels
– Arteries = vessels that carry blood away
from the heart
– Veins = vessels that carry blood to the
– Capillaries = very small blood vessels that
distribute blood to all parts of the body
Respiratory System
• Alveoli = tiny air sacs in the lungs through
whose walls gases such as oxygen and
carbon dioxide diffuse in and out of the
• Lungs expand and contract about 12–20
times a minute at rest
Respiratory System
• This system supplies oxygen to the body, carries carbon
dioxide away
• Pressure changes brought about by the contraction and
relaxation of the diaphragm and rib muscle allow air to be
drawn from the atmosphere into throat and eventually flow
from the bronchi to air sacs called alveoli
• Gas exchange occurs at the alveoli and allows oxygen to
return to the heart and systemic system while removing
carbon dioxide.
• The ability to pick up and deliver oxygen is critical for the
functioning of the body
The Heart
• The heart is divided into two halves by a wall (septum)
and each half is divided into an upper chamber (atrium)
and a lower chamber (ventricle).
• The heart is a double pump. The right heart (pulmonary:
lungs) has the task of transporting deoxygenated blood to
the lungs where it can exchange carbon dioxide for a
fresh supply of oxygen.
• From the lungs, the oxygen-rich blood enters the left side
(systemic: body) so that it can be sent out to the rest of
the tissues in the body.
• The tissues extract their oxygen and give up waste
products (carbon dioxide), to the blood. The blood returns
to the right side of the heart where the cycle begins again.
Blood Flow Pattern
Left Atrium
Mitral Valve
Left Ventricle
Pulmonary Artery
Pulmonary Valve
Right Ventricle
Aortic Valve
Right Atrium
Superior Venae Cavae
Arteries of each organ
Arterioles of each organ
Capillaries of each organ
Circulation in the Heart
Cardiorespiratory System At Rest and With
Heart Rate
50-90 bpm
Up to 170-210 bpm
12-20 breathes per minute
40-60 breathes per minute
Blood Pressure
(Systole=Contraction Diastole=Relaxation)
Cardiac Output (SV x HR)
5 quarts/min.
20 or more quarts/min.
Energy is required to fuel vital body functions and represents the capacity to perform
physical work.
Metabolism is “The sum of all the chemical processes necessary to maintain the body.”
The rate at which your body uses energy (metabolic rate) depends on your level of
More Active → More Energy
Energy from food
– Broken down into glucose
– Stored as glycogen
ATP (adenosine triphosphate): The energy “currency” of cells
The body converts chemical energy from carbohydrates, fats, protein into
substances that cells can use as fuel (ATP).
ATP is the primary energy source for biological work.
These fuels can be used immediately or stored.
ATP must be restored at the same rate it is being used.
There are 3 major energy systems the body uses to produce ATP
Body’s Energy
Energy Systems
Duration of activity
for which system
Non-oxidative Oxidative
0-10 seconds
10 seconds-2
> 2 minutes
Low to moderately
Intensity of activity
for which system
Rate of ATP
Immediate, very
Slower, but
Muscle stores of
glycogen and
Body stores of
glycogen, glucose,
fat, and protein
Oxygen used?
Sample activities
Weight lifting, picking
up a bag of
400 meter run,
groceries, jumping
running up a flight of
1500 meter run, 30
minute walk, long,
slow jog
Energy System Facts
• Lactic Acid is produced in the non-oxidative
system which interferes with muscle
contraction. Thus fatigue sets in.
• Activities performed at less than 50% of
one’s oxygen capacity → primarily use fat!
• Activities sustained above 80% of one’s
capacity → carbohydrates.
• Fat is not utilized as a fuel source during
high-intensity anaerobic activity because
the lactic acid blocks epinephrine, a fatmobilizing hormone, which makes fat
available from it storage units.
Energy System Facts
• Anaerobic activity are fueled entirely by
carbohydrate metabolism which is a limited
source of ATP.
• For exercise to be aerobic, the intensity is such
that the oxygen needs can be adequately met by
the body during the activity – a “steady state”
between supply and demand.
• Oxidative ATP production occurs in the
mitochondria. The mitochondria can use either
glucose or fats to produce ATP, based upon
Effects of Regular Cardio-Respiratory
Endurance Exercise
Immediate effects
Increased level of neurotransmitters
and certain hormones, especially
epinephrine which stimulates a rise in
all body functions
Constant or slightly increased blood
flow to the brain.
Increased heart rate and stroke volume
(amount of blood pumped per beat).
Increased pulmonary ventilation
(amount of air breathed into the body
per minute). More air is taken into the
lungs with each breath and breathing
rate increases.
Reduced blood flow to the stomach,
intestines, liver, and kidneys, resulting
in less activity in the digestive tract and
less urine output.
Increased systolic blood pressure;
Increased blood flow and oxygen
transport to working skeletal muscles
and the heart;
Increased oxygen consumption. As
exercise intensity increases, blood
levels of lactic acid increase.
Increased energy (ATP) production.
Increased blood flow to the skin and
increased sweating to help maintain a
safe body temperature.
Long-term effects
Improved cognitive functioning and ability to
manage stress; decreased depression,
anxiety, and risk for stroke.
Increased heart size and resting stroke
volume; lower resting heart rate.
Risk of heart disease and heart attack
significantly reduced.
Improved ability to extract oxygen from air
during exercise.
Reduced risk of colds and upper respiratory
tract infections
Increased sweat rate and earlier onset of
sweating, helping to cool the body.
Increased blood volume and capillary
Higher levels of high-density lipoproteins
(HDL) and lower levels of triglycerides; lower
resting blood pressure and reduced platelet
stickiness (a factor in coronary artery
Reduced risk of colon cancer and certain
other forms of cancer.
Increased number and size of mitochondria
in muscle cells;
increased amount of stored glycogen;
increased myoglobin content;
improved ability to use lactic acid and fats as
All of these changes allow for greater energy
production and power output.
Insulin sensitivity remains constant or
improves, helping to prevent Type 2
Fat-free mass may also increase somewhat.
Increased density and breaking strength of
bones, ligaments, and tendons; reduced risk
for osteoporosis.
Decreased body fat.
The Effects of Exercise
Immediate Effects:
*Increase in HR, since higher demand for oxygen.
*Increase in BP, as a result of ↑ blood flow.
*Increase in supply, delivery, and use of oxygen by
*Increase in body temperature.
*Increase in certain hormones, especially
epinephrine which stimulates a rise in all body
*Increase in metabolism.
The Effects of Exercise
Long-term (Training) Effects
*Heart function and the ability to carry oxygen to the body is improved with endurance exercise.
*Capacity of cells to take up and use oxygen improves.
*Increased size of the heart: the walls become thicker and stronger, allowing for greater efficiency.
*Increased blood volume, (the amount of plasma) therefore, more blood is pushed into circulation with
each contraction.
*Increased stroke volume – the amount of blood pumped with each contraction.
*Improved cardiac output (SV x HR): the amount of blood pumped per minute.
*Decreased resting pulse rate: as stroke volume increases, the body’s need for blood will be met with
less beats per minute.
*Decreased exercise pulse rate, heart operates more efficiently, with longer periods of rest.
*Faster resting pulse rate recovery after exercise.
*Reduced resting BP with endurance training.
*Increased blood flow to the skin and sweating to release heat.
*Decrease in the amount of body fat.
*Increased size of muscle fibers.
*Increased muscle strength and endurance.
*Improved respiratory responses – depth of each breath increases, muscles that support breathing
improve, better efficiency of system.
*Reduced stress.
Metabolic Responses
• Improves Maximal Oxygen Consumption (VO2
Max )- This is determined by the body’s ability to
uptake, distribute, and utilize oxygen.
• There is a limit to the body’s ability to transport
and use oxygen and is determined partly on
genetics and partly on fitness status. The is the
best overall assessment of the cardiorespiratory
• The more fit you are, the more oxygen the blood
carries, the higher the rate the oxygen is
distributed to the tissues and the higher the levels
of oxygen extracted from the blood at the
capillary level.
• The improvement in VO2 Max is caused by
physiological adaptations:
– Increased size and number of mitochondria
(powerhouse of cell) where oxygen is utilized
to produce ATP.
– Enzymes needed by mitochondria to produce
ATP ↑, thus more energy.
– Increase in cardiac output, thus more oxygen
available and extracted to use.
Cardiorespiratory Endurance
• PURPOSE of a CRE Program is to develop the body’s ability to
deliver oxygen to the working muscles and tissues.
• The quantity and quality of activity will differ based on the goals of
health-related benefits or fitness-related benefits.
HEALTH-RELATED BENEFITS – Include a reduced risk of certain
diseases through moderate activity, but can occur without any
significant change in an individual’s functional capacity or physical
FITNESS-RELATED BENEFITS-require a higher level of activity. These
benefits are related more to performance levels in sport and higher
levels of lifestyle activities. When fitness-related benefits are
achieved, health-related benefits also occur.
Benefits of a CRE Program
• Reduced risk of chronic disease.
– Cardiovascular disease – CRE training has positive effects on serum
lipids such as cholesterol and triglycerides. High levels of cholesterol can
lead to a heart attack and stroke because they contribute to formation of
fatty deposits in the arteries.
– Cancer – CA is the second leading cause of death in U.S. Studies have
shown a decreased risk of colon cancer, breast and reproductive system
– Diabetes – Regular exercise helps prevent the development of Type II
diabetes. Obesity is a key risk factor for diabetes and exercise helps
keep body fat at healthy levels. Exercise burns excess sugar and makes
cells more sensitive to insulin.
– Osteoporosis – Exercise helps to prevent loss of bone density and poor
bone strength.
Benefits of CRE Program
• Better Control of Body Fat
-Body chemistry is influenced by endurance exercise and results in a
better regulated energy balance.
-Exercise burns calories directly and continues to do so by raising
resting metabolic rate for several hours following exercise.
-Increased proportion of lean body mass.
• Improved Immune Function
-Exercise can be either positive or negative on the immune system. It
depends on the amount of exercise. Moderate exercise enhances
immune function, while overtraining depresses the immune system.
-Diet, stress management and sleep will also play a role in immune
Evaluating CRE
• There are simple tests to measure or estimate the VO2 max or your
level of cardio-respiratory fitness.
• In lab, a 1.5 mile run or a 1 mile walk will be administered.
• Other tests include a 3 minute step test or a bicycle test or treadmill
Setting Goals
*You can use your CRE assessment results to set a specific VO2
goal and improve your fitness category.
*The amount of improvement depends on age, health status, and
initial fitness level.
*Another type of goal can be a time or distance goals.
*Achieve the Surgeon General’s goal of 30 minutes/day, expending at
least 150 calories.
• FREQUENCY – Recommended 3-5 days/week for normal, healthy
individuals. Highly fit individuals may do daily activity. Training less
than 3 days/week will not improve fitness.
• INTENSITY – This is the most important component in achieving
training effects. Intensity is inversely related to duration. Follow a
plan of Progressive Overload, in which the amount of exercise is
progressively increased, as the body adapts to the demands of
exercise placed upon it by improving its functioning.
-To determine intensity follow one of these methods:
A. Percentage of Max Heart Rate
B. Percentage of Heart Rate Reserve
C. Rate of Perceived Exertion (RPE)
Monitoring Your Heart Rate
• Carotid artery in the neck
• Radial artery in the wrist
• Count beats for 10 seconds and multiply
the result by 6 to get rate in beats per
Heart Rate
Maximum Heart Rate: 220 – age = _________bpm
55% intensity = MHR x .55 = ___________bpm
90% intensity = MHR x .90 = ___________bpm
Target heart rate range = _______bpm to ________bpm
220 – 20 = 200 bpm
200 x .55 = 110 bpm
200 x .90 = 180 bpm
Target heart rate range = 110-180 bpm
Heart Rate Reserve
Step 1: Maximum Heart Rate: (Male ) 220 – age = _________bpm
(Female) 226 – age = _________bpm
Step 2: Find HR Reserve: MHR – Resting HR = HRR
Step 3: Find % of HR reserve (50% - 85%)
HRR x .50 = _______bpm (low end)
HRR x .85 = _______bpm (high end)
Step 4: Find target HR range
Target HR range = % of HRR + resting HR
Ratings of Perceived Exertion (RPE)
• Ratings of perceived exertion
• When you are training in your
target heart rate zone, you
should rate intensity as
somewhat hard to hard. It is
usually quite accurate.
• Talk test
FITT Principles
~ Time (Duration)– The length of time depends upon the intensity.
Lower Intensity → More time (45-60 Min.)
Higher Intensity → Less time (20 min.)
ACSM recommends 20 – 60 minutes of continuous aerobic activity. If
intermittent activity is incorporated, a minimum of three 10-minute
bouts should be accumulated over the day.
Longer duration, low-to-moderate intensity activities usually result in
more gradual gains in max oxygen consumption.
~ Type – Cardio-respiratory endurance exercises include activities that
involve the rhythmic use of large muscle groups for an extended
period of time.
Examples: Jogging, walking, cycling, kickboxing, swimming, skiing
• Rate of Progression depends on age, health status, initial level of
fitness, goals and motivation! It is specific to the individual.
• Your fitness improves when you overload your body
• Initial stage (3–6 weeks): 3–4 days per week, low end of target heart
rate zone, 20–30 minutes
• Improvement stage (4–6 months): 3–5 days per week, middle to
upper end of target heart rate zone, 25–40 minutes
Maintaining Cardiorespiratory Fitness
Maintenance Stage
Improvements to fitness are not indefinite
There comes a time when your fitness levels will
reach a limit
By the 4th – 6th month, you may reach an
acceptable level of fitness and wish to maintain
this by continuing every 3rd day
Reaching this level requires setting new goals or
adjustments to maintain motivation
Cross-training can help boost enjoyment and
prevent injuries
Components of a Cardiorespiratory
Exercise Session
• WARM-UP – It is important to prepare the body for activity. It is
important to increase muscle temperature before more intense work.
• AEROBIC CONDITIONING – This phase should follow all the FITT
principles. It is important to sustain the exercising HR for 20-60
minutes at the appropriate exercising intensity.
• COOL-DOWN – This is important to gradually return the body to a
normal resting rate. Plan a cool down for about 10-15 minutes. This
is a great time to perform flexibility work.
• Whenever you participate in physical activity, there is a chance for
• A fitness assessment is crucial prior to exercise.
– Dehydration – “Thirst is not an accurate means for measuring or
determining dehydration.” You have already started the dehydration
process when you sense thirst. Hydrate early. Drink before, during, and
after a workout!
– Heat Injuries
• Heat Cramps – The least serious of the heat-related injuries. Associated with
activities that involve prolonged, profuse sweating. Usually caused by muscle
fatigue, especially with children. Need to stretch, replace fluids, rest.
• Heat Exhaustion – Involves rapid, weak pulse, low bp, dizziness, profuse
sweating, muscular weakness, some cases disorientation. Replace fluids,
• Heat Stroke – CALL 911 – Dangerously elevated body temperature, failure of
brain’s temperature regulatory system, life threatening, hot dry skin, cessation
of sweating, sudden collapse with confusion or loss of consciousness, erratic
behavior. Victim needs to be cooled as soon as possible!
• Hypothermia – Core body temperature drops,
sleepiness, low metabolic rate. A body temperature of 95
degrees or less signals the onset of hypothermia.
Dampness, wind and fatigue can also cause hypothermia.
Signs include change in mental status, cold abdomen,
shivering, loss of coordination, difficulty speaking. Dress
properly, cover head and hands, layer clothing.
• Frostbite – Freezing of body tissues. Usually occurs in
exposed body parts – earlobes, fingers, toes. Can cause
permanent damage.
• Take into account wind chill when exercising
Wind Chill
Source: National Weather Service
• Cryotherapy, or externally applying ice, is one of the best and
immediate treatments for activity related injuries. Ice constricts the
blood vessels to help with swelling.
• R – REST the injured site.
• I – ICE the injury regularly for 36-72 hours after an injury or until all
the swelling is gone. Apply the ice for 15-20 minutes, then remove for
at least 30 minutes.
• C – COMPRESSION – Wrap the site in an effort to reduce
swelling and fluid collection. An elastic bandage works well.
• E – ELEVATION -Elevate the injured limb to reduce swelling and
pain. Ideally raise the injured area above the heart, placing the
injured area on pillows.
Heat is appropriate for most injuries after 72 hours or after all the
swelling is gone.
• Do not attempt to self-diagnose or train through pain. Pain is an
indicator that something is wrong and activity should be stopped until
the source of pain is identified and your physician gives permission to
begin again.
• Wear Proper Shoes – Consult with an experienced athletic shoe
salesman for proper shoes.
• Environmental Conditions – Take into consideration temperature, air
pollution, wind-chill, altitude and humidity when exercising outdoors.
Dress appropriately for the conditions.
• Illness – Use common sense when ill. If you have a cold (above the
neck) and no fever, a light workout may be appropriate. If a fever is
present, extreme fatigue, muscle aches, flu-like symptoms, avoid
exercise until well.
• Night Exercise – Be responsible and visible. Wear white clothing,
reflective gear. Use a flashlight. Stay in a safe, well-lit area. Don’t
go alone! Carry ID. Face oncoming traffic when possible. Let
someone know your route and expected time back.
• Without a strong heart, nothing else
matters. Perform weekly aerobic exercise
to condition the body!