HR Response to Exercise

James BarracloughCardiac Dynamics during Exercise

Lesson 18AS PE Anatomy & Physiology Starter/Recap Quizbustershttp://www.teachers-direct.co.uk/resources/quiz-busters/quiz-busters-game.aspx?game_id=105530

Homework Answers

Aims: Cardiac Dynamics during ExerciseObjectives:ALL learners to understand:HR/SV/Q response to exerciseThe pulseThe trained heartSOME learners will be able to apply this to real life situations in sportHR Response to ExerciseHR increases rapidly depending on exercise intensityTypically increases linearly in proportion to intensity (i.e. more intense = higher HR)Until reaches maximum HR (220 your age)What is yours?Just before exercise commences HR increases (ANTICIPATORY RISE)Caused by release of hormones (e.g. adrenaline) causing SA node to increase HRIf exercise is submaximal/steady, HR may plateau into STEADY STATEThis represents point where O2 demand being met by supplyPost-exercise (recovery) HR remains elevated to allow removal of waste products (e.g. lactic acid/CO2)

HR Response to Exercise

Activity 1Draw curves to show HR curves for typical exercises at:Submaximal (low intensity) done for youMaximal (high intensity)Fluctuating (e.g. football, rugby)

ALSO: what does anticipatory rise mean& what causes it?HR (bpm)

preexercise recovery exercise

SV Response to ExerciseStroke Volume = volume of blood pumped out of heart with each contraction (stroke)As with HR increases linearly with increasing intensity

BUT plateaus at 40-60% of max effort (see next slide)

One reason = shorter diastolic phase (less time for ventricular filling) from increased HR near maximal effort

12Stroke Volume Response

SV Response to Exercise2 reasons why SV can increase during exercise:Increased Venous Return:Volume of blood returning to RA from bodySignificantly increases during exercise due to muscle pump Frank-Starling Mechanism:Ventricles stretch more & contract with greater forceTherefore pump more blood from heartIncreased venous return means more blood into ventricles during diastolic phaseVentricles stretch more & contract with more forceTrained athletes have lower HR so have more time for ventricles to fill with bloodThis stretches cardiac tissue further & means higher stroke volume

ACTIVITY 2: provide definitions to the above

Cardiac Output Response to ExerciseCardiac Output = volume of blood pumped per min:

Cardiac Output = Stroke Volume x Heart Rate(Q) (SV)(HR)

Easy to predict as SV & HR both increase linearly & plateau at max exercise capacity(see next slide)

CARDIAC OUTPUT (Q) = ability of heart to circulate blood in body delivering O2 to working muscles

MAX EXERCISE Q may reach 4 8x resting values

Cardiac Output Response

Activity 3: Values for Rest/ExerciseComplete table for HR, SV & Q for trained/untrained:

VariableDefinitionApproximate resting valueApproximate submaximal valueApproximatemaximal valueHeart RateStroke VolumeCardiac Output Activity 3 Answers VariableDefinitionApproximate resting valueApproximate submaximal valueApproximatemaximal valueHeart RateAmount of times heart beats per minuteUntrained = 60bpmTrained = 30 60bpm%age of MHR220 - ageStroke VolumeAmount of blood ejected from LV pre beatUntrained = 60 80mlTrained = 80 110mlUntrained = 100 120mlTrained = 160 200 mlUntrained = 100 120mlTrained = 160 200mlCardiac Output Amount of blood ejected from LV in 1 minuteUntrained = 5L/minTrained = 5L/minUntrained = 10 15L/minTrained = 15 20L/minUntrained = 20 30L/minTrained = 30 -40L/minActivity 4 - The PulseGive definition of the pulse:Pressure wave generated from heart each time LV pumps blood into aortaIncreased pressure causes slight dilation of arteries as blood travels throughWhere are most common pulse sites (5 in total) & can you show where each is?Radial artery (wrist)Carotid artery (neck)Femoral artery (groin)Brachial artery (arm)Temporal artery (temple)

Recap Mind Map

Homework Answer following questions on trained heart:Give 6 differences in trained hearts using following as guideline:CARDIAC HYPERTROPHYBRADYCARDIA (HEART RATE)INCREASED VASCULARISATIONMYOCARDIUM & VENTRICULAR WALLSSA NODE firing rateSTROKE VOLUMECARDIAC OUTPUTSTARLINGS LAWDIASTOLEWhat is the ejection fraction and how is it calculated?REVISE FOR TEST ON HEART/CARDIAC CONDUCTION/ DYNAMICS

232323Next Lesson...Revision Test of Cardiac System