THE PHYSIOLOGY OF FITNESS

The body’s response to acute exercise

Part Two: Respiratory Response

Session Outcomes

List two responses of the respiratory system to acute exercise

Describe the processes involved in one response of the respiratory system

Explain why the process occurs and the benefits it generates for exercise

Recap :Responses to physical activity Can be acute or

chronic Acute – body’s

immediate responses to exercise

Chronic – adaptations to the body that occur through regular training

Responses to physical activityRespiratory responses:

1. Increased breathing rate

2. Increased tidal volume

Respiratory Responses – Neural & Chemical Control

Breathing is a highly complex process controlled by neural and chemical factors

Largely under involuntary control by the respiratory centres of your brain

Breathing involves two actions:

- inhalation (an active process)

- exhalation (a passive process)

Respiratory Responses – Neural & Chemical Control

1. Stretch receptors in lungs detect increase in rate and depth of breathing

2. The respiratory centres (the medulla and pons) send nerve impulses to the respiratory muscles that controls breathing frequency and tidal volume each breath

3. The respiratory centres are responding to central nervous system and peripheral nervous system information.

4. Other information comes from chemorereceptors (i.e. within aortic arch and carotid bodies) and mechanoreceptors in joints, tendons and active muscles that assess movement and metabolic status

2. Increased tidal volume

Tidal Volume is the amount of air breathed in and out in each breath (approx 500cm3 at rest)

Only two-thirds (350cm3) reaches the alveoli where gaseous exchange occurs.

During exercise, tidal volume increases to allow more air to pass through the lungs

The volume of air passing through the lungs each minute is know as the ‘minute volume’ (breathing rate x tidal volume).

Tidal volume is elevated by both aerobic and anaerobic exercise. During exercise, oxygen depletion triggers a deeper tidal volume to compensate

Respiratory responses1. Increased breathing rate

A minor rise in breathing rate has been recorded prior to exercise – this is know as ‘anticipatory rise’.

When exercise begins there is an immediate and significant increase in breathing rate.

This is believed to be a result of receptors working in both muscles and joints

Respiratory responses1. Increased breathing rate

Muscles demand more O2 after changes in exercise intensity

CO2 increase as result of increased energy production

Breathing rate increases to satisfy these demands

The capillary network surrounding the alveoli expands.

This results in increased blood flow to the lungs and increased pulmonary diffusion

Anticipatory response

Exercise Intensity

Breathing Rate

Breathing rate increases with exercise intensity as more oxygen is required for energy production

If intensity continues to rise breathing rate will plateau when athlete reaches their maximal level for oxygen consumption (Vo2 max)

Breathing rate will plateau if exercise intensity remains the same

Respiratory responses1. Increased breathing rate

Changes in the concentration of CO2 and O2 in the blood are detected by the respiratory centre which increases the rate of breathing

The intercostal muscles, diaphragm and other muscle which aid the expansion of the thoracic cavity work harder to further increase the expansion during inhalation, to draw in more air.Lungs

Heart

Body

Cardiovascular responses2. Activity response

Oxygen demand by muscles many times greater during exercise than at rest

Increased oxygen delivery accomplished by: Increase in heart rate – b.p.m.

increase with exercise intensity Increased cardiac output Redistribution of blood flow to

skeletal muscle

Recap

http://www.teachpe.com/cross/breathing_mechanisms.htm

2. Activity response – Increased Cardiac Output

Cardiac output (SV x HR) increased by: Increase in heart rate Increase in stroke volume

Oxygen uptake by the muscle also increases as intensity increases

2. Activity response - Redistribution of blood flow

Blood flow to working skeletal muscle increased

Blood flow to less active organs (liver, kidneys, gastrointestinal tract) decreased

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Redistribution of blood flow during exercise

Heart muscle

GI tract

Kidneys

Bones

Brain

Skin

Muscle

Heavy/intense exercise, short duration, e.g. 400 m

Cardiac output

Rest

5 litre/min 25 litre/min

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Acute response to exercise

Cardiovascular responses: Increased heart rate x Increased

stroke volume → increased cardiac output

Redistribution of the blood around the body, 20% to skeletal muscle increases to 80–85% during exercise

Investigation into acute cardiovascular responses

20 minute Cardio session x2 Subject 1: 3 tier intensity – walk – Steady

state jog – run (6min intervals) Measurements and results taken every 6

minutes Subject 2: Interval training session – 3

minute jog, 1 minute sprint (4 minute intervals)

Measurements and results taken every 4 minutes

Heart Rate monitors required Blood pressure monitors required

3. Increased Blood Pressure

BP is the pressure of blood against the walls of your arteries.

Normal BP 120/80 Systolic BP – Highest pressure within

bloodstream. Occurs when the heart is in systole (contacting)

Diastolic BP – Lowest pressure within bloodstream. Occurs when the heart is in dyastole (relaxing, filling with blood)

3. Increased Blood Pressure

Oxygen consumption and HR increases in relation to the intensity of the activity

Systolic pressure rises progressively why??

Diastolic pressure stays the same or decreases slightly

Pulse rate rises and blood flow to muscles increases

Vasodilation & Vasoconstiction Vasodilation – Vascular portion of active muscles increases

through dilation of arterioles. Increased diameter of blood vessels results

in increased blood flow to muscles Vasoconstriction – Contraction of arterioles Decreased diameter of blood vessels results

in reduced blood flow to the muscles

TASK

In small groups produce a poster presentation on an elite athlete showing the acute cardiovascular responses to their activity.

Session Outcomes

Explain the term ‘acute response’ Describe two acute responses of the

cardiovascular to exercise Investigate acute responses during short

term exercise Evaluate acute responses after short

term exercise