In six months, you are leaving with a group of scientists for South America to study newly discovered bones of the largest dinosaur yet found. You can't fly in to the remote site as there are no landing strips for airplanes. You have to carry everything you need on your back. As you think about carrying heavy loads uphill for long distances, you realize that you have to design a workout program to get your body ready. With that in mind, you start a workout program with physical activities that you enjoy that will result in preparing you for your expedition.
All machines are essentially alike.
They need a source of energy, they occasionally need to be repaired, and they need to be used regularly to make sure they work well. The human body is just like a machine. It uses food, vitamins and minerals as a source of energy. It needs to be repaired occasionally, which can be as simple as a cut finger that heals on its own to a broken bone that needs a doctor's help. Very importantly, the human body needs to be used regularly to make sure it works well.