How Does a Range of Intensity or Duration During Exercise Affect a Human's Heart Rate?

How does a range of intensity/duration during exercise affect a human's heart rate?

Introduction

The human heart is widely considered as the core of the human anatomy, pumping blood to every inch of the human body, it helps us sustain oxygen and nutrients. However, at times, this process is accelerated, this can be due to many factors, (such as emotional situations) nevertheless the main focus today is exercise.

Today I shall experiment to see to what extent exercise affects a human's pulse rate. My choice of independent variables is between intensity and duration of exercise. Intensity would include changing how faster or the amount of exercise been done during a fixed time. Whereas duration is keeping the intensity of the exercise constant, but changing the amount of time the take place. Duration is my choice, although it is more time consuming, it should be easier to count time rather than intensity (such as individual steps), and this focus on measuring intensity might give us unreliable results.

Prediction

I believe there will be a strong positive correlation between the duration of exercise and heart rate. The longer the time period, the higher the individual's heart rate should rise.

This might lead you to ask why I believe heart rate corresponds to the amount of exercise done; this is explained by scientific theory.

Theory

Why does our heart rate differ at certain times or in certain situations? This can be explained by our bodies' need for more energy during these situations.

While exercising, our body goes through an amazing process, the pumping of rich-oxygenated blood and the refuelling of oxygen-depleted blood. This process takes place in the circulatory system (which is closely entwined with the respiratory system).

The Heart. The heart is the core of the circulatory system, it acts a pump, constantly beating and pumping blood through the whole of an individual's life. In fact the heart acts as two pumps, to be specific the right side pumps de-oxygenated blood to the lungs to collect oxygen and remove carbon dioxide, while the left side pumps this oxygenated blood to the body (the left side has more muscle because it need more force to push blood around the whole body) (This is why the circulatory system is sometimes referred to as the 'double' circulatory system).

Process of circulation (heart)

(Technically we can start the process from any stage because this is constantly happened over and over again).

1. The right atrium receives de-oxygenated blood via vena cave (not mentioned in the diagram, but its right next to the right atrium, it's like a tunnel where it receive the blood from).

2.