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C H A P T E R 9. CARDIOVASCULAR AND RESPIRATORY ADAPTATIONS TO TRAINING. w Examine metabolic adaptations that occur due to endurance training. (continued). Learning Objectives. w Learn how cardiorespiratory endurance differs from muscular endurance.

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C H A P T E R 9

CARDIOVASCULAR AND RESPIRATORY ADAPTATIONS TO TRAINING

slide2

w Examine metabolic adaptations that occur due to endurance training.

(continued)

Learning Objectives

w Learn how cardiorespiratory endurance differs from muscular endurance.

w Review how cardiorespiratory endurance is measured.

w Find out what changes occur in the oxygen transport system as a result of endurance training.

slide3

Learning Objectives

w Discover how adaptations to cardiovascular, respiratory, and metabolic function affect an athlete's endurance capacity.

w Learn why cardiorespiratory adaptations benefit performance in both endurance and nonendurance sports.

slide4

Muscular Endurance

  • Ability of a single muscle or muscle group to sustain repetitive or static exercise
  • Related to muscle strength, muscle blood flow and muscle oxidative and anaerobic capacities

Cardiorespiratory Endurance

w Ability of the whole body to sustain prolonged, steady-state exercise

w Related to cardiovascular and respiratory system (aerobic) development

Endurance Training

slide5

.

VO2max

w Highest rate of oxygen consumption attainable during maximal large muscle mass exercise like running, cycling, etc.

w Can be increased with aerobic, or endurance, training

Submaximal Endurance Capacity

wClosely related to competitive endurance performance; determined by VO2max and lactate threshold

.

w More difficult to evaluate since there is no one physiological variable that can be measured to quantify it

w Can also be increased with endurance training

Evaluating Endurance Capacity

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CHANGES IN VO2MAX WITH TRAINING

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Cardiovascular Variables Affected by Training

w Heart size (ventricular muscle mass and chamber diameter)

w Stroke volume

w Heart rate

w Cardiac output

w Tissue blood flows

w Blood pressure

w Blood volume

slide8

w Evaluated with the Fick equation:VO2 = SV ´ HR ´ a-vO2 diff

.

Oxygen Transport System

w Components of the cardio-respiratory system that transport O2 to the tissues

w O2 transport increases at VO2max with endurance training because of a large increase in SV and a smaller increase in a-vO2 diff; the greater a-vO2 diff is because of the increased oxidative capacity of the muscles and the increased capillary density, which results in an increase in transit time, thus allowing more time for diffusion of oxygen from the RBC to the muscle mitochondria

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DIFFERENCES IN HEART SIZE

Left ventricular chamber diameter

Interventricular septal thickness

slide10

DIFFERENCES IN HEART SIZE

Posterior wall thickness

Left ventricular mass

slide11

DIFFERENCES IN HEART SIZE

(Mean wall thickness)

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Key Points

Heart Size Adaptations

w The left ventricle changes the most in response to endurance training.

w The internal dimensions of the left ventricle increase mostly due to increased ventricular filling.

w The wall thickness of the left ventricle increases (hypertrophies), allowing a more forceful contraction of the left ventricle.

slide14

STROKE VOLUME AND TRAINING

Remember there is great variance in SV response to exercise. The important thing is that during both submaximal and maximal exercise, endurance trained subjects have a higher stroke volume than untrained subjects.

slide15

Subjects SVrest (ml) SVmax (ml)

Untrained 50-70 80-110

Trained 70-90 110-150

Highly trained 90-110 150-220

Stroke Volumes (SV) for Different States of Training

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Blood Volume Distribution at Rest

Guyton, Medical Physiology, 1981

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THE MUSCLE PUMP

During exercise the muscle pump

functions to increase the return of blood to the heart, or increase venous return

The “thoracic pump” resulting from increased ventilation has the same effect in increasing venous return to the heart

slide19

Key Points

Stroke Volume Adaptations

w Endurance training increases SV at rest and during submaximal and maximal exercise.

w End diastolic volume increases, caused by an increase in blood plasma volume and greater diastolic filling time, contributing to increased SV.

w The increased size of the heart allows the left ventricle to stretch more and fill with more blood; wall thickness increases enhance strength of contraction. Reduced systemic blood pressure (after load) lowers the resistance to the flow of blood pumped from the left ventricle.

slide20

Resting Heart Rate

w Decreases with endurance training likely due to greater venous return to the heart and changes in autonomic control (↑ parasympathetic and ↓ sympathetic activity)

w Sedentary individuals can decrease resting HR by 1 beat/min per week during initial training, but several recent studies have shown small changes of less than 3 beats/min with up to 20 wk of training

w Highly trained endurance athletes may have resting heart rates of 30 to 40 beats/min – Peter Snell’s resting HR was 28 b/min

slide21

Submaximal

w Decreases proportionately with the amount of training completed

w May decrease by 10 to 30 beats/min after 6 months of moderate training at any given rate of work, with the decrease being greater at higher rates of work

Maximal

w Remains unchanged or decreases slightly

w The slight decrease might allow for optimal stroke volume (i.e., more filling time) to maximize cardiac output

Heart Rate During Exercise

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Which Comes First?

Does increased stroke volume allow a decreased heart rate or does decreased heart rate allow an increased stroke volume?

slide24

Heart Rate Recovery Period

w The time after exercise that it takes your heart rate to return to its resting level

w With training, heart rate returns to the resting level more quickly after exercise

wHas been used as an index of cardio-respiratory fitness

w Conditions such as altitude or heat can affect it

w Should not be used to compare individuals to one another, but to monitor training effects in the same individual

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Resistance Training Effects on HR

Resistance training can lead to decreases in heart rate; however, these decreases are not as reliable or as large as those that occur with endurance training.

slide27

.

w After training, Q decreases slightly or does not change at rest or during submaximal exercise.

.

w Q is higher at maximal exertion after training due to the increase in maximal SV.

.

w Absolute values of Qmax range from 14 to 20 L/min in untrained people, 25 to 35 L/min in trained individuals, and 40 L/min or more in large endurance athletes.

Key Points

Cardiac Output Adaptations

slide29

Muscle Blood Flow Increases with Training during Maximal Exercise

w Increased cardiac output

w Greater blood flow distribution to the active muscle fibers away from inactive tissues and inactive muscle fibers

slide30

Key Points

Blood Pressure and Training

wEndurance training results in reduced blood pressure at the same submaximal work rate, but at maximal work rates systolic pressure increases and diastolic pressure decreases.

w Resting blood pressure (both systolic and diastolic) is lowered with endurance training in individuals with borderline or moderate hypertension.

w Blood pressure during lifting heavy weights can cause marked increases in systolic and diastolic blood pressure, but resting blood pressure after resistance training tends to not change and may decrease.

slide32

wChanges in plasma volume are highly correlated with changes in SV and VO2max.

.

Key Points

Blood Volume and Training

wEndurance training, especially intense training, increases blood volume.

wBlood volume increases are due primarily to an increase in plasma volume (increases in ADH and aldosterone, and plasma proteins cause more fluid to be retained in the blood).

wRed blood cell volume increases, but the increase in plasma volume is higher; thus, hematocrit decreases.

wBlood viscosity decreases, thus improving circulation and enhancing oxygen delivery.

slide34

Cardiovascular Adaptations to Training

In Review:

w Left ventricle size and wall thickness increase

w Resting, submaximal, and maximal stroke volume increases

w Maximal heart rate stays the same or decreases

w Maximal cardiac output increasesandcardiac output is better distributed to active muscles

w Blood volume increases, as does red cell volume (but to a lesser extent)

w Resting blood pressure does not change or decreases slightly, while blood pressure during submaximal exercise shows small decreases

slide35

.

The most important contributor to the increase in VO2max results from the increases in cardiac output and muscle blood flow. The increase in a-vO2diff also plays a role. This increase in a-vO2diff is due in part to a more effective distribution of arterial blood away from inactive tissue to the active tissue, which also has an increased oxidative capacity, so that a higher percentage of the blood coming back to the right atrium has gone through active muscle.

Effects of Training on the Fick Equation

slide36

Once an athlete has achieved her genetically determined peak VO2max, she can still increase her endurance performance due to the body's ability to perform at increasingly higher percentages of that VO2max for extended periods. The increase in performance without an increase in VO2max is primarily a result of an increase in lactate threshold.

.

.

.

Genetic Limits on VO2max

slide38

w The a-vO2diff increases with training due to more oxygen being extracted by tissues.

Key Points

Respiratory Adaptations to Training

w Pulmonary ventilation increases during maximal effort after training primarily by increasing performance of the inspiratory muscles (strength and endurance).

w Pulmonary diffusion increases at maximal work rates.

w The respiratory system is seldom a limiter of endurance performance.

w All the major adaptations of the respiratory system to training are most apparent during maximal exercise.

slide39

Respiratory exchange ratio

w decreases for submaximal efforts (greater use of FFAs), and

w increases at maximal levels.

.

Oxygen consumption (VO2) is

w unaltered or slightly increased at rest,

w unaltered or slighted decreased at submaximal rates of work, and

.

w increased at maximal exertion (VO2max—increases range from 0% to 93% in different studies).

Metabolic Adaptations to Training

Lactate threshold is shifted to the right.

slide40

.

CHANGE IN RACE PACE, NOT VO2MAX

slide41

.

Factors Affecting VO2max

Level of conditioning—the greater the beginning level of conditioning the lower the response to training

Heredity—accounts for slightly less than 50% of the variation as well as an individual’s response to training

Age—decreases with age are associated with decreases in activity levels as well as decreases in physiological function

Gender—lower in women than men (20% to 25% lower in untrained women; 10% lower in highly trained women)

Specificity of training—the closer training is to the sport to be performed, the greater the improvement and performance in that sport

slide43

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VO2MAX COMPARISON IN BROTHERS

slide44

.

VO2MAX CHANGES AND AGE

slide45

.

IMPROVEMENT IN VO2MAX WITH TRAINING

slide46

.

INCREASE IN VO2MAX FOR TWINS

slide47

.

VO2MAX AND SPECIFICITY OF TRAINING

slide48

Cardio-Respiratory Endurance Training

w Major defense against fatigue which limits optimal performance.

w Should be the primary emphasis of training for health and fitness.

w All athletes can benefit from maximizing their endurance.

slide50

Thought Question

Why would you expect the RER to increase during maximal exercise after training? Remember, after training, a person can exercise at higher intensities for longer periods of time.

slide51

MEASURING HEART SIZE

Two-dimensional

echocardiography

(uses ultrasound)

slide52

Muscle Blood Flow Redistribution after Training

Submaximal

Steady State

% changes in blood flow after training before and during low-intensity treadmill exercise in muscles composed primarily of ST (S), FTa (R), mixed fiber type (M), and FTb fibers (W) in the rat. Note the data for steady state exercise (15 min).

Armstrong and Laughlin, Am J Physiol 246: H59, 1984

slide53

Components of the Increase in VO2max with Training

A: Changes after several months of training starting from sedentary

B: Changes after several years of intense training starting from sedentary

Saltin and Gollnick, Handbook of Physiology, 1983

slide54

Thought Question

Consider the Fick equation. What would happen if training induced an increase in cardiac output and muscle blood flow during maximal exercise, but did not induce an increase in capillaries in the muscles?