The aim of my investigation is to measure the effects of BMI (body mass index) on heart rate recovery after a period of exercise.

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The aim of my investigation is to measure the effects of BMI (body mass index) on heart rate recovery after a period of exercise. I aim to take the BMI of several test subjects who are of similar age and record their recovery times for before and after exercise. I aim to obtain reliable, valid and accurate results which represent each of the BMI classifications for our age group.


I predict that “As the BMI of an individual increases, the resting heart rate after exercise will increase”. Moreover,  “If an individual’s BMI is above 25 (overweight), their recovery time after exercise will be longer than that of an individual with a lower BMI (20 for example)”. This is because the heart the heart will be weaker and so is harder to pump blood around the body; there also may be a build up of fatty deposits which block the passageways for the blood to flow, making the heart work twice as hard.  I have chosen this hypothesis as I believe it would be the most effective in affecting recovery rate.


I will be investigating the effects of BMI (body mass index) on heart rate recovery after a period of exercise.  The heart rate is the time it takes for the heart to return to its resting heart rate (in terms of BPM).

BMI (body mass index) is the index that is used to identify whether the weight of an individual is healthy for their height. BMI classifies the weights of people into underweight, average weight, or overweight. A BMI of below 18.5 is referred as underweight, a calculation between 18.5 and 24.9 is referred to as being healthy (average) and a calculation of between 25 and 30 is considered overweight. For my project, I have two test subjects from each BMI classification.

 To calculate BMI you must:

  • Find your weight and height
  • Divide your weight (in kg) by your height (in metres) and the final result will be your BMI.

The circulatory system

Most of the cells in the human body require the circulatory system to act as a transport service for them. Two fluids move through the circulatory system: blood and lymph. The blood, heart, and blood vessels form the Cardiovascular System. The lymph, lymph nodes and lymph vessels form the Lymphatic

System. The Cardiovascular System and the Lymphatic System make up the

Circulatory System.

Blood is the body’s internal transportation system. Pumped by the heart, blood travels through a network of blood vessels, carrying nutrients (O2, glucose) and hormones to the cells and removing waste products (CO2. urea) from the 100 trillion cells of our body.

The central organ of the cardiovascular system is the heart. This is a hollow, muscular organ that

Contracts at regular intervals, forcing blood through the circulatory system.

  • The pulmonary circulation- which is a short loop from the heart to the lung and back again
  • The systemic circulation- which send blood from the heart throughout all the parts of the body and then back again to the heart.

Both systems are contained within the heart, blood, and blood vessels.

  1. The heart can be thought of as two pumps sitting side by side – each of which has an upper atrium and a lower ventricle – a total of 4 chambers. It functions as two pumps inside one.
  2. The right side of the heart pumps ‘deoxygenated blood’ (actually, blood low in oxygen) from the body into the lungs, where gas exchange takes place. In that process, carbon dioxide is lost to the air and oxygen is absorbed. This oxygen is almost all carried by the Red Blood Cells
  3. The left side of the heart pumps oxygenated blood from the lungs to the rest of the body.
  4. The heart is enclosed in a protective sac, which surrounds the heart and secretes a fluid that reduces friction as the heart beats.
  5. The atria (upper chambers) of the heart receive blood coming into the heart. Then have thin walls, so allowing them to be filled easily. They pump the blood into the ventricles (lower chambers), thus filling them.
  6. The ventricles pump blood out of the heart and the left ventricle has the thickest walls of the heart because it has to do most of the work to pump blood to all parts of the body. This is where the blood has the highest pressure

Keeping a healthy heart rate recovery has been shown to be greatly beneficial to an individual’s overall health and well-being. Individuals with an abnormal value for heart rate recovery may have a three to five percent per year risk of a major health problem, compared to one percent per year risk for individuals with a normal heart rate. There are several factors that have been known to contribute to a person’s heart rate recovery.

Risk of being Overweight:

If you are overweight, you may develop:

  • Cardiovascular (heart and blood circulation) disease
  • High blood pressure
  • Diabetes
  • Certain types of cancer, such as colon and breast cancer.

If you are overweight, you increase your death rise. For example, if your BMI is 25, you increase your death rise slightly (by 20 or 30%) as BMI rises from 25 to 27. As BMI rises above 27, the risk of death rises more steeply (by 60%).

Risk of being Underweight:

If you are Underweight, you may develop:

  • Compromised immune system
  • Respirator Disease
  • Digestive Disease
  • Cancer
  • Osteoporosis
  • Increased Risk of falls and fractures

The Circulatory System is known as a closed system because the blood is contained within either

The heart or blood vessels at all times – always flow in one direction. The path is the same –

Heart (ventricles) → arteries → arterioles → organ (capillaries) → veins → heart (atrium)


Except for the capillaries, all blood vessels have walls made of 3 layers of tissue. This provides for both strength and elasticity:

 A. The inner layer is made of epithelial tissue.

 B. The middle layer is smooth muscle.

 C. The outer layer is connective tissue.

Arteries and arterioles

Arteries carry blood from the heart to the capillaries of the organs in the body.

The walls of arteries are thicker than those of veins. The smooth muscle and elastic fibres that make up their walls enable them to withstand the high pressure of blood as it is pumped from the heart. The force that blood exerts on the walls of blood vessels is known as blood pressure and it cycles with each heart-beat. Each artery expands when the pulse of blood passes through and the elastic recoil of the fibres cause it to spring back afterwards, thus helping the blood along. This is known as secondary circulation, and it reduces the load on the heart. Other than the pulmonary arteries, all arteries carry oxygenated blood.

The aorta carries oxygenated blood from the left ventricle to all parts of the body except the lungs. It has the largest diameter (25mm) and carries blood at the highest pressure. As the aorta travels away from the heart, it branches into smaller arteries so that all parts of the body are supplied. The smallest of these are called arterioles. Arterioles can dilate or constrict to alter their diameter and so alter the flow of blood through the organ supplied by that arteriole. Examples include muscles (when running) and skin (when hot or blushing). Since the volume of blood remains the same, if more blood flows through one organ, less must flow through another.

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After leaving the capillaries, the blood enters a network of small venules, which feed into veins. These, in turn, carry the blood back to the atria of the heart. The walls of veins are thinner and less elastic than arteries, but they are also more flexible.

Veins tend to run between the muscle blocks of the body and nearer to the surface than arteries. The larger veins contain valves that maintain the direction of blood-flow. The flow of blood in veins is helped by contractions of the skeletal muscles, especially those in the arms and ...

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