How does exercise affect pulse rate?

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How does exercise affect pulse rate?

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I am doing an investigation to find out how exercising affects peoples pulse rate. Your pulse is the rate at which blood is pumped around the body by the heart. We measure this in bpm (beats per minute) because this is the most practical way to measure it. The variables that can have an effect are how long a person exercises for, whether the exercise is high or low impact and how fit the person is. The input variable is how much/little the person exercises and the output variable is the persons pulse rate.

I am going to investigate if exercising for different periods of time affects somebody’s pulse rate. I will do this with a group of five people (including me), each person will exercise for periods of 2, 4, 6, 8 and 10 minutes. We chose these times because we felt that exercising over a 10 minute period will show more changes in pulse rate, exercising for less than 10 minutes may not produce as good results as your pulse rate may not vary as much. People may not be able to exercise constantly for more than 10 minutes so we thought that 10 minutes was an adequate time. Also, we chose to take the pulse every two minutes, rather than every minute so that we can see a bigger change.

The exercise we will be doing is ‘step ups’; this is where you repeatedly step up and down one step. The step that we will be undertaking this activity on is 28cm high. I think that this form of exercise is fairly low impact considering the speed and length of time we will be doing it for.

Respiration happens in every cell, it is the process of converting glucose and oxygen to energy.

Glucose + oxygen → carbon dioxide + water + energy

Respiration happens in the muscle cells (to make us move), so when we suddenly need to move faster the muscles require more oxygen and glucose to produce more energy, so that the muscles can move faster.

Your blood contains plasma which carries just about everything around your body, but most importantly for respiration oxygen carrying red blood cells (oxygen is carried round the body as oxyhaemoglobin) and glucose. When you start exercising your heart, (which pumps the blood around the body) needs to beat faster to get the oxygen and glucose to the muscle cells where it is needed, so that respiration can take place. You then need to breathe at a more rapid rate to provide more oxygen (breathing is the only way to get more oxygen), so that it can get absorbed into the blood stream and carried to where it’s needed. This is how respiration is linked to pulse rate.

I predict that the more we exercise the faster our pulse rate will be, to a certain extent. This is because our pulse rate will increase with exercise, as more oxygen and glucose are needed at the muscle cells so that respiration can take place to produce energy. Therefore the heart will need to pump faster to get the blood around the body (as it is the blood plasma in the blood which carries glucose and the red blood cells which carry oxygen around the body as oxyhaemoglobin), so it will complete more bpm. However, the body cannot keep doing this for ever so I think that at some point your body’s oxygen supply will reach the oxygen demand.

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The body can either reach the oxygen demand aerobically (with oxygen) or anaerobicly (without oxygen). If the body cannot supply enough oxygen to the muscles aerobically (converting glucose and oxygen to energy) it will start producing energy anaerobicly, which means that glucose gets converted into energy without using oxygen, so your body produces a waste product (lactic acid) which causes you to get a ‘stitch’.

Glucose → energy + lactic acid

This way you will acquire an ‘oxygen debt’ which means that you will have to keep breathing hard for a while to get oxygen to ...

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