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Exercise and Heart rate, Stethoscopes and Heart Model

Public summary: 

Why does your heat beat faster after exercise? Come and find out why in this demonstration where you are the subject.

When you exercise your heart beats faster!
Useful information
Kit List: 

(When done on tour, this experiment is often integrated with the Stethoscopes experiment. The Stethoscope experiment requires stethoscopes and antibacterial wipes/disinfectant and tissue, and also lives in a small blue box, often with the stopwatches. If using the stethoscopes, ensure you read the separate risk assessment for Stethoscopes).

Packing Away: 

Lives in one of the small blue medic boxes.

Frequency of use: 

Exercise and Heart Rate

Check for asthma. If child is asthmatic, check with parents about severity, and if the child can do five minutes of fairly heavy-impact exercise. If they can do it, ensure they have an inhaler, and ensure they don't push themselves too far.

Take child's pulse (radial side of forearm), and write it down.

Make child run on the spot 3 mins and then do starjumps for 3 mins or any other combination of the above.

Check pulse again.

There should be a difference. If not, it's an anomaly, and you can make them do the experiment again.

If you're doing this experiment by taking the radial pulse, you need to start by asking questions (like "Have you had your pulse taken before/seen it done on TV?" and "Why do doctors take your pulse?" to make sure they know that your pulse reflects your heart rate, and if they don't, make sure to explain it before carrying on!

So, why does your heart rate go up?

What is the heart for?
-They will usually say say pumping blood around the body/beating. My favourite question after this is "What is blood for?", to which the answer is always "It keeps you alive". You can then progress from here by asking why (which they often will not know, even in surprisingly old children), and then explaining why we need blood. I usually go along the lines of "What do we need to do to stay alive?", get them to work out that we need to breathe, eat and drink, then think about where air and food go into our bodies, and then how might we be able to transport these things from your lungs/stomach to wherever they're needed, like your muscles to jump around or your brain to think - and then you have ended up working out what blood does! (You can use the analogy of lots of lorries (blood cells) driving along roads (blood vessels) carrying cargo (oxygen/food). You can go further into the idea of cells needing energy from glucose and oxygen with older/interested kids.)

- With older/interested children you can then develop the idea by talking about the heart as a double pump and the pulmonary and systemic circulatory systems. This works well if you've got the heart model to hand (on tour), or if someone else has just explained the heart model to them!

-Then you can talk about how your muscles are more active when you're doing exercise so they need more 'fuel' (oxygen and glucose), therefore you need to get more blood to them in a shorter space of time, therefore the heart beats faster!

-You can also talk about breathing rate (are they panting?) and recovery times and fitness if you wish to. You need to breathe at a higher rate and more deeply to get more oxygen into your lungs, and then move it to the muscles more quickly, because they need more energy and so are using up oxygen faster.

(N.B. I find this experiment is quite useful with groups of lively children, as provided you can get them to be reasonably sensible and you have enough space, they can jump up and down until they're quite tired and then they will often sit down calmly and listen to the explanation afterwards!)

Heart Model and Diagrams

-let the kids take the model apart and let them figure out how it all fits together

-What is “circulation” and why do we need it (see below)
-Structure and function of the heart
-Things that can go wrong (valve defects, heart attack etc)

It is quite surprising how little most people know about circulation. It is therefore very important to find out how much the kid knows already and work from that. I have included a very basic script for explaining circulation below- you would obviously have to adapt that to the age of the kid and to what he/she knows already.



Look at the whole model. Ask the kids what it is (heart) and what it is used for (they will usually say that it pumps blood). Now comes the tricky bit: Why does the heart pump blood? It is quite surprising that many kids (and parents) have no idea about why we might want to pump blood through our body. If this happens, here is an explanation you could use to explain the basics of circulation (I have used a very simple one that even young kids can understand- you would have to adapt that for older kids/parents):

- Our body is made out of loads of little building blocks called cells. Each cell is like a small factory and it needs two things
- get the kids to think about what these two things may be; i.e. why do we breathe (to get oxygen); why to we eat (to get food/nutrients)
-so the factories in our body need food and oxygen
-where do they get that from? Ask them where the food they eat goes (stomach); similarly, the air they breathe in goes to the lungs
-so if the food is in the stomach and the oxygen is in the lungs, how can it ever get to all the “factories” that make up the brain, your toes etc.
- you need something like a street- these “streets” are your blood vessels
-you also need something to transport the food and oxygen, i.e. a lorry –this “lorry” is the blood
-so our blood transports food and oxygen to all the cells in our body
-but there is a problem- blood is a liquid- ask them what happens when you pour water/get water from the tap (water always “goes down”- so if this happens to our blood as well, it would all end up in our toes).
- so you need something that makes the blood go to the cells in the brain as well; i.e. you need an engine to drive a lorry or in other words, you need the heart to pump the blood through your body


Let them take the heart apart and get them to think about what the individual bits may be and what they might be used for. Here are some things you could point out:

-can they see the big blood vessels (“streets”) that come into and out of the heart; get them to think where they might come from and where they may go to; i.e. some go to/come from the lungs and others go to/come from the body (having explained circulation beforehand helps; i.e. the blood has to go to the lungs to pick up oxygen); let them guess which ones might be the vessels that go to the lungs and which ones are the ones that go to the body

- The heart has chambers –can they see them? How many are there?- how does the blood travel through the heart?

- do they think that the blood can go back to the chamber it just came from? No; point out valves; if the kids are older, get them to figure out why this “one way” system is important

- the heart is a muscle; it contracts, when it contracts, the chamber gets smaller, this squeezes the blood in that chamber into the next chamber/ into the body/ to the lungs; valves prevent backflow


- Can they see the small blood vessels going into the heart itself (coronary arteries etc)? Why is this important? – the heart is a muscle, that has to work all the time for all your life- it needs a lot of food and oxygen, too!!! What do they think happens if you block one of these vessels?
Ischaemia, angina, heart attack (Parents are usually quite interested in this)

-What can you do when this happens? Open up vessels (stents), make vessels bigger (drugs; vasodilators); but most importantly, remove anything that can block those vessels- this is why a healthy diet, exercise and stopping smoking are so important!

-Other things that can go wrong: Valve defects, heart failure

-When the heart pumps, it makes a noise- this is what you can hear with a stethoscope; refer them to the stethoscope experiment


Using a stethoscope to listen to the heart and find out how it works
Use the 'heart rate and exercise' explanation too!

1. Do they know what it is?

2. Do they know what it's used for?
- Use it to listen to: Lungs, Heart, Bowel sounds, Bruits (noise due to turbulence in blood vessels for various reasons) in the following vessels:

1. Carotid
2. Femoral
3. Thyroid
4. Hepatic

3. What makes the sound?

Normal Lungs:
-Normally turbulent air going in and out of bronchi.
-Sounds different over bronchi/trachea and lung fields.
-Same noise, but in the lung fields it is heard through large amounts of other tissue and so is soften (I think it cuts out specific frequencies - high or low -but don't quote me on that).

Abnormal Lung (probably talk about Asthma as most kids now about it)

1) Bronchial breathing over lung fields.
Due to consolidation - solid debris in lungs with pneumonia- or fribrosis.
Means sound can't 'disperse' (I'm sure physicists would have better description).

2) Wheeze (can demonstrate this one).
Due to narrowing of the tubes.
Asthma wheeze, COPD gives polyphonic.
Tumour wheeze gives monophonic (because only blocks one tube).

b. Heart.
i. Have brief discussion about what heart does (see Heart Rate and Exercise or Heart Model explanations). Where is your heart? It is surprising how many children seem to think it's somewhere in their left shoulder!

ii. What makes noise in heart?
Valves - with older kids a discussion about why we have valves may be useful.

iii. Normal heart sounds.
- Lub-dub.

iv. Extra heart sounds:
Note, can have third and fourth heart sounds.
If you have both they make noise like train going over tracks - du-dub-du-dub.

v. Abnormal:
Due to turbulent flow through valves (make the noises).
Why do you get turbulent flow? - Valve doesn't fully open (stenosis) or Valve doesn't fully close (regurgitation)

Risk Assessment
Date risk assesment last checked: 
Sun, 26/01/2020
Risk assesment checked by: 
Date risk assesment double checked: 
Mon, 27/01/2020
Risk assesment double-checked by: 
Beatrix Huissoon
Risk Assessment: 

Heart rate before and after up to 6mins of exercise.

Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Over-exertion Asthma attack. 2 5 10 Check child's asthma status with parent or with teacher (or with child itself if old enough) before doing experiment. Do not allow child to exercise if asthma is severe, and DO NOT ALLOW AN ASTHMATIC CHILD TO DO EXPERIMENT IF THEY DO NOT HAVE AN INHALER.
In case of an attack, sit child down, keep them calm, locate inhaler for child to self-administer. Call first aider.
1 5 5
Running children Child running into things/people. 4 2 8 Make sure exercise area is clear, use on-the-spot exercise e.g. star jumps if space is limited.
Call a first aider in the event of injury.
2 2 4
Exercise Physical injury e.g. falling. 2 2 4 Demonstrator to ensure floor area is clear and dry. If area becomes wet, locate a mop and dry the area. Call first aider in case of injury. 1 2 2
Small Parts in Heart Model Small parts could be swallowed. 2 4 8 (The heart model is suitable for older children, so hopefully shouldn't be an issue). Do not let children play with experiments unattended. Call first aider in case of ingestion and encourage the child to cough. 1 4 4
Pointed Parts in Heart Model Some parts have fairly sharp points - risk to eyes/skin. 2 3 6 Sharp points filed down to be as safe as reasonably possible. Call a first aider in case of injury. 2 2 4
Earpieces of Stethoscopes Transferring infection via ear pieces. 3 2 6 Wipe ear pieces with antiseptic wipes or tissues and disinfectant before use and after you or a child has used it. 1 2 2
Stethoscopes Yanking of stethoscope causing injury 3 2 6 Keep children under control, and if children are misbehaving, don't give them a stethoscope. Call first aider if necessary. 1 2 2
Stethoscopes If using stethoscopes in Heart Rate and Exercise experiment, risk of injury from swinging stethoscope if child starts jumping/running whilst wearing it. 2 2 4 Ensure stethoscopes are removed before doing exercise. In case of accident, call a first aider. 1 2 2
Stethoscope Choking from stethoscope being tangled around neck. 2 4 8 Keep children under control, and if children are misbehaving, don't give them a stethoscope
Ensure stethoscopes are removed before doing exercise. Call first aider if necessary.
1 4 4
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