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AS Module 1B.1

AQA AS / A Level Physical Education AS 5581 A 6581

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AQA ExaminationsAS / A Level Sport and Physical Education

AS 5581A 6581

Module 1 Part B

Physiological Factors which Improve Performance

AS Module 1B.2


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There are three ways to measure heart performance in sport and exercise:

Heart Rate

64 beats per minute is a typical

result for a fit person at rest.

The total amount of blood pumped out of the heart in one beat.

Definitions of Heart FunctionDefinitions of Heart Function

The number of times the heart beats per minute.

Stroke Volume

Heart Rate Stroke Volume Cardiac Output

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Cardiac output

• Cardiac output

– volume of blood ejected by left or right ventricle per minute

• Q = stroke volume (mL/beat) x heart rate (beats/min)

– Average Q approx 5.25 L/min (70 mL/beat x 75 beats/min)

• Similar to total blood volume of ~5 litres (male)

• Cardiac reserve

– maximal Q – resting Q

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Stroke volume

• Stroke volume (SV)– volume of blood ejected by a ventricle during

systole • depends on:

– Preload• Degree of stretch prior to contraction

– Contractility• Forcefulness of contraction

– Afterload• Pressure that must be exceeded before

ejection of blood from ventricles can occur

(Starlings Law)

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For example…

Stroke Volume = 75 ml Heart Rate = 65 b.p.m.Cardiac Output = 75 x 65

= 4875 ml

Stroke Volume = 150 ml Heart Rate = 200 b.p.m.Cardiac Output = 150 x 200 = 30000 ml

Cardiac Output

At rest…

While exercising…

Cardiac output is…

…the total output of blood from the heart in one minute.

It is calculated using the formula…

Cardiac Output = Stroke Volume x Heart Cardiac Output = Stroke Volume x Heart RateRate

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HEART DYNAMICSAVERAGE RESTING HEART RATE VALUES• MALES - 70 bpm• FEMALES - 72 bpm

CARDIAC OUTPUT

The Resting Heart

• = SV x HR (this is the formula used for each calculation)• SV = stroke volume - measured in ml (cm3)

AT RESTuntrained person endurance athlete• = 75 (ml) x 70 (bpm) = 109 (ml) x 48 (bpm)• = 5.25 l min-1 = 5.23 l min-1

– (or dm3 min-1)

DURING MAXIMAL EXERCISEuntrained person endurance athlete• = 120 (ml) x 200 (bpm) = 190 (ml) x 200 (bpm)• = 24 l min-1 = 38 l min-1

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FACTORS REGULATING THE HEARTNEURAL

NERVES FROM THE CARDIAC CONTROL CENTRE (CCC)

RECEPTORS• provide sensory information to CCC used in regulation of HR and SV• proprioceptors located in muscles / joints

– detect muscle stretching and joint angles changing• central and peripheral chemoreceptors

– detect changes in blood pH (H+ ion concentration), O2, CO2, K+ levels

• baroreceptors in aorta and carotid arteries – detect changes in blood pressure

Heart Rate Response to Exercise

PO SI TI VE( increases HR

and SV)

SY MPATH ETI C(nervous system )

N EGATI VE(decreases HR

and SV)

PAR ASY MPATHETI C(nervous system )

M EDU LLA O BLO NG ATA

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FACTORS REGULATING THE HEARTHORMONAL

ADRENALINE (fright - flight - fight)• stimulates HR by

GLYCOGENOLYSIS (the conversion of glycogen to glucose - a rapid process)

• and breakdown of fats and proteins (slow)

• these processes release energy

NOREPINEPHRINE• this is a form of adrenaline

released by the sympathetic neurones acting directly on the pacemaker

• increases HR and SV

INTRINSIC

• increased TEMPERATURE of myocardial tissue

• increased VENOUS RETURN– stimulates SA node and

hence HR– Starling’s Law of the heart


OTHER FACTORS

• AGE• GENDER• POSITION OF BODY• EXERCISE• STATE OF HEALTH

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Regulators of the Heart: Factors Influencing Stroke Volume

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Distribution of blood flow (Q) during rest and heavy exercise

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SHORT-TERM EFFECTS OF EXERCISE ON THE HEART

INTERPRETATION OF GRAPH


a - anticipatory rise due to hormonal actions of adrenaline and norepinephrine

b - sharp rise, mainly anaerobic work– due to proprioceptor / sensory

stimulation– continued release of hormones– and action of muscle pump

c - continued high HR due to maximal work loads which continue to stress

anaerobic systems

– producing lactic acid (H+) + CO2 + K+ which stimulate chemoreceptors

– intrinsic factors are also stimulated at maximal level

d - steady state and some recovery of O2 debt

e - rapid recovery due to cessation of proprioceptive stimuli / muscle pump / withdrawal of hormones, fast recovery of PC stores

f - slow recovery, clearance of metabolites (like lactic acid)– heat loss hence muscle cooling– general body systems returning to pre-exercise levels

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SHORT-TERM EFFECTS OF EXERCISE ON THE HEART


DIFFERENCES BETWEEN INDIVIDUALS

• patterns of recovery vary

• gender• state of health• values of max HR vary

according to formula :• HRmax = 220 - age

approximately

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LONG-TERM EFFECTS OF EXERCISE ON THE HEART

At rest During exercise

Heart rate Av. 72 bpm Max. 22-0 – age in years

Cardiac output (Q) Av. 5 l/min 20 – 25 l/min

Stroke volume Av. 70 ml 140 mlMost studies use data taken from male subjects. Values for females may differ

When CV improvements are made and efficiency is increased, Q could be higher to compensate for the reduction to the HR. However as the SV will have increased through training the increase in Q may be small

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