Exercise Physiology

Cardiorespiratory Physiology

Cardiovascular System

• Functions:• Supply muscles & organs with oxygen• Deliver nutrients to muscles & organs• Remove metabolic by-products from

active tissues• Like???

• Functions accomplished due to blood

Heart Structure

• 4 Chambers:• 2 Atria- receive blood from body; upper chambers• 2 Ventricles- send blood to body; lower chambers

• Right & Left Sides:• Right- receives from body & sends blood to lungs;

deoxygenated blood• Left- receives from lungs & sends blood to body;

oxygenated blood

Heart Structure

Blood Vessels & Blood

• 3 Major Types:

1. Arteries: carry blood away from the heart

2. Capillaries: site of substance exchange

3. Veins: carry blood back to the heart

Blood Vessels & Blood

• Red blood cells contain hemoglobin• Molecule made of protein & iron• Capable of bonding to & transporting 4 oxygen

molecules

• Amount of oxygen being transported is dependent upon partial pressure of oxygen (PO2)

• In lungs, PO2 is high, oxygen binds easily

• Near tissues in body, PO2 is low, oxygen unloads & allows diffusion

Cardiorespiratory Connection

http://www.youtube.com/watch?v=mH0QTWzU-xI

Respiratory System

• Functions:• Deliver oxygen to the blood• Remove carbon dioxide from the blood• Aid in acid-base (pH) balance of the blood

Respiratory Structures

• Nose & Mouth:• Filter, humidify, & adjusts temperature of air

• Trachea:• Passageway for air only

• Bronchi:• Tubes that allow air to enter the lungs

Respiratory Structures

• Lungs:• Right (larger) & Left • Divided into lobes• Soft & spongy• Contain alveoli

• Alveoli

• Tiny air sacs• Site of gas exchange (diffusion)

• Movement of molecules from areas of high concentration to low concentration until equilibrium

Respiratory Structures

Ventilation

• 2 phases:• Inspiration- movement of air into the lungs• Expiration- movement of air out of the lungs

• http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter49/alveolar_pressure_changes_during_inspiration_and_expiration.html

Ventilation

• Breathing rate & depth increases with exercise• Why?

• Not due to need for more oxygen• Due to need to rid body of carbon dioxide & maintain

blood pH• Allows for more gas exchange to occur• Efficiency of gas exchange increases

Gas Exchange

Measuring Heart Rate

• Heart Rate (HR)• Number of times the heart beats in 1 minute• Units = bpm (beats per minute)

• Resting HR • 40 bpm – 70 bpm

• Heart Rate changes due to body’s need to eliminate CO2

• CO2 becomes carbonic acid in the blood & alters pH

• Exercise HR can be 200+ bpm

Measuring Heart Function

• Stroke Volume:• The amount of blood pumped out of the left ventricle

with each heartbeat• Units = mL or L

• Cardiac Output:• The amount of blood pumped into the aorta each

minute• Units = mL or L per minute• Cardiac output = stroke volume x heart rate

Measuring Blood Pressure

• Normal = 120/80 mm Hg

• Systolic pressure• Estimates the heart’s work & pressure against walls of

arteries• Occurs during ventricular contraction

• Diastolic pressure• Indicates the blood pressure in the body outside of

the heart • Occurs during ventricular relaxation

Measuring Cardiorespiratory Function

VO2 Max:

maximal volume of oxygen that can be consumed in a given amount of time during maximal effort

Measures aerobic powerUnits = mL of oxygen/kg of body wt/min

VO2 Max

Peaks between 18-25 years of age

Sedentary but healthy 20 year old…Male: ~40 ml/kg/minFemale: ~36 ml/kg/min

Trained athletes…Male: 80-90 ml/kg/minFemale: 75-85 ml/kg/min

Measuring Cardiorespiratory Function

• Arterial-Venous Oxygen Difference (a-v O2 difference)

• Difference in the amount of oxygen present in the blood when it leaves the lungs and when it returns to the lungs

• Increase in this value reflects more oxygen use• Example:

• At rest = 4-5 mL O2 /100 mL of blood

• During exercise = 15 mL O2 /100 mL of blood

Immediate Response to Exercise• Heart Rate: Increases

• Blood Pressure: • Systolic increases• Diastolic no change

• Stroke Volume: Increases (to a point)

• Cardiac Output: Increases

• a-v O2 difference: Increases

Immediate Response to Exercise

• Bohr Effect• Exercise causes body temperature to rise• Hemoglobin is less effective at holding onto oxygen• Results in more oxygen being released to working

tissues

Training (Long Term) Effects

• Increased heart size• Larger atria & ventricles• Thicker heart wall

• Increases rate of contraction & volume of blood emptied from chambers per beat

• Results in:• Decreased resting heart rate• Increased stroke volume• Increased cardiac output

Training (Long Term) Effects

• Increased capillarization• Improved substance exchange

• Reduced risk of cardiac disease & heart attack

• Improvements in a-v O2 difference

• Oxygen extraction from blood improved

• Increases # and activity of mitochondria• More oxidative phosphorylation

Training (Long Term) Effects

• Increase total blood volume• Hormone erythropoietin (EPO) stimulates red blood

cell production

• Results in:• Increased amount of oxygen carried by blood• Increased oxygen extraction by muscles

• Altitude Training

Prescribing Cardiorespiratory Exercise

• Maximum HR• 220-Age (in years)

• Exercise intensity is often prescribed as a % of max HR

• Recommendation for typical sedentary adults 70-85% max HR• Changes to this range (above, below or within) are

based on goals for exercise

• Relationship between intensity & duration of exercise?

Prescribing Cardiorespiratory ExerciseIntensity % max HR Comments

Very Light < 50% Often prescribed for elderly exercisers

Light 50-63% Recovery

Moderate 64-76% Builds endurance; burns more fat

Hard 77-93% Appropriate for younger, more physically fit individuals; burns more carbohydrates

Very Hard >94% Should only be used for interval training; cannot be maintained for long periods of time

Maximal 100% Should not be used