lecture 11 (physiology of trainning)

8/12/2019 Lecture 11 (Physiology of Trainning)

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(c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 13:

The Physiology of TrainingEffect on VO2 MAX, Performance,

Homeostasis and Strength

EXERCISE PHYSIOLOGY

Theory and Application to Fitness and Performance, 5thedition

Scott K. Powers & Edward T. Howley

Presentation revised and updated by

TK Koesterer, Ph.D., ATC

Humboldt State University


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Objectives

Explain the basic principles of training: overload andspecificity

Contrast cross-sectional with longitudinal research

studies

Indicate the typical change in VO2 MAXwith endurancetraining programs, and the effect of the initial

(pretraining) value on the magnitude of the increase

State the VO2 MAXvalues for various sedentary, active

and athletic populations

State the formula VO2 MAXusing HR, SV and a-v O2

difference; indicate which of the variables is most

important in explaining the wide range of VO2 MAX

values in the population


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Objectives

Discuss, using the variables identified in objective 5,

how the increase in VO2 MAXcomes about for the

sedentary subject who participates in an endurance

training program

Define preload, afterload, and contractility, anddiscuss the role of each in the increase in the

maximal SV that occurs with endurance training

Describe the changes in muscle structure that are

responsible for the increase in the maximal a-v O2difference with endurance training

Describe the underlying causes for the decrease in

VO2 MAX that occurs with cessation of endurance

training


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Objectives

Describe how the capillary and mitochondrial changes

that occur in muscle as a result of an endurance training

program are related to the following: a lower O2deficit,

and increased utilization of FFA and a sparing of blood

glucose and muscle glycogen, a reduction in lactate andH+formation, and an increase in lactate removal

Discuss how changes in central command and

peripheral feedback following an endurance training

program can lower the HR, ventilation, andcatecholamine responses to a submaximal exercise bout

Contrast the role of neural adaptation with hypertorphy in

the increase in strength that occurs with resistance

training


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Exercise

A Challenge to Homeostasis

Fig 13.1


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Principles of Training

Overload

Training effect occurs when a system isexercised at a level beyond which it is

normally accustomed Specificity

Training effect is specific to the musclefibers involved

Type of exercise

Reversibility

Gains are lost when overload is removed


7/36(c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Research Designs to

Study Training

Cross-sectional

studies

Examine groups ofdiffering physical

activity at one time

Record differences

between groups

Longitudinal studies

Examine groups

before and aftertraining

Record changes

over time in the

groups


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Stroke Volume

and Increased VO2max

Increased SVmax

Preload (EDV)

Plasma volume

Venous return

Ventricular volume

Afterload (TPR)

Arterial constriction

Maximal muscle blood flow with nochange in mean arterial pressure

Contractility



Factors Increasing Stroke Volume

Fig 13.2



a-vO2Difference and

Increased VO2max Improved ability of the muscle to extract

oxygen from the blood

Muscle blood flowCapillary density

Mitochondial number

Increased a-vO2difference accounts for 50%of increased VO2max



Factors Causing Increased VO2max

Fig 13.3



Detraining and VO2max

Decrease in VO2max

with cessation of

trainingSVmax

maximal a-vO2difference

Opposite of training

effect

Fig 13.4



Endurance Training

Effects on Performance Improved performance following endurance

training

Structural and biochemical changes inmuscle

Mitochondrial number

Enzyme activity

Capillary density



Structural and Biochemical

Adaptations to Endurance Training

Mitochondrial number

Oxidative enzymes

Krebs cycle (citrate synthase) Fatty acid (-oxidation) cycle

Electron transport chain

NADH shuttling system Change in type of LDH

Adaptations quickly lost with detraining



Detraining

Changes in Mitochondria

About 50% of the increase in mitochondrialcontent was lost after one week of detraining

All of the adaptations were lost after fiveweeks of detraining

It took four weeks of retraining to regain theadaptations lost in the first week of detraining


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Mitochondrial Number and

ADP Concentration on VO2

[ADP] stimulates mitochondrial ATP

production

Increased mitochondrial number followingtraining

Lower [ADP] needed to increase ATP

production and VO2


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MitochondrialNumber and

ADP

Concentrationon VO2

Fig 13.7


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Eff t f E d T i i


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Effects of Endurance Training

on O2Deficit

Fig 13.8


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Biochemical Changes

and FFA Oxidation

Increased mitochondrial number and capillary

density

Increased capacity to transport FFA fromplasma to cytoplasm to mitochondria

Increased enzymes of -oxidation

Increased rate of acetyl CoA formation

Increased FFA oxidation

Spares muscle glycogen and blood

glucose


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FFA Oxidation and

Glucose-Sparing

Fig 13.9


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Blood Lactate Concentration

Balance between lactate production andremoval

Lactate production during exercise

NADH, pyruvate, and LDH in thecytoplasm

Blood pH affected by blood lactateconcentration

pyruvate + NADH lactate + NADLDH

Mit h d i l d Bi h i l


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Mitochondrial and Biochemical

Adaptations and Blood pH

Fig 13.10


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Blood Lactate Concentration

Fig 13.11


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Biochemical Adaptations

and Lactate Removal

Fig 13.13


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Links Between Muscle and

Systemic Physiology Biochemical adaptations to training influence

the physiological response to exercise

Sympathetic nervous system (E/NE)

Cardiorespiratory system (HR, ventilation)

Due to:

Reduction in feedback from musclechemoreceptors

Reduced number of motor units recruited

Demonstrated in one leg training studies


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C f


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PeripheralControl of

Cardiorespiratory Responses

Fig 13.15

C t l C t l f


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CentralControl of

Cardiorespiratory Responses

Fig 13.16


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Physiological Effects of

Strength Training Strength training results in increased muscle

size and strength

Neural factors Increased ability to activate motor units

Strength gains in initial 8-20 weeks

Muscular enlargement Mainly due enlargement of fibers

(hypertrophy)

Long-term strength training

N l d M l Ad t ti


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Neural and Muscular Adaptations

to Resistance Training

Fig 13.17

lecture 11 (physiology of trainning)

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