Running improves the blood supply
When off on a run, your heart rate (measured in beats per minute) and stroke volume (the amount of blood pumped out by your heart per beat) both increase as the muscles are fed with oxygen. Oxygen is transported in the blood. The amount of oxygen-rich blood that flows out of the heart is called your cardiac output (CO). Runners will see an increased CO over time as they train.
Being able to pump out more blood per minute means the heart isn't having to work as hard as it once did in order to deliver the same amount of oxygen. This accounts for the fact that your resting heart rate (RHR) drops as you get fitter. For example, running a ten-minute mile could take your heart up to 160bpm, but following a few weeks training, running at the same pace might result in your heart rate only reaching 140bpm. The only way the heart rate will touch 160bpm is if you run faster.
Oxygen-rich blood travels through a vast network of tiny capillaries, which allow the exchange of gases, nutrients and waste products. Once the blood arrives at the muscles, it picks up the oxygen, offloads some carbon dioxide and it makes its way back to the heart. Muscle cells don’t, however, take all the oxygen that the blood is carrying. Regular running increases the ability of the muscles to extract more oxgen by triggering the growth of additional capillaries in the muscle. Therefore running is good for you because it improves blood supply.The average non-runner has three to four capillaries per muscle fiber while a well-trained runner might have five to seven per fiber.The maximum rate at which oxygen can be extracted and used by the muscle is the VO2 max that you may have heard of. VO2 is partly determined by gender (women have a lower VO2 max than men) genetics and age, but it will improve with regular running.
Running builds muscle strength
When enough oxygen is flowing through the bloodstream to meet energy needs, the muscle cells, (the mitochondria), are able to use that oxygen to produce energy. It does this by breaking down a special substance called adenosine triphosphate (ATP). Our bodies can generally only store enough ATP to last for approximately two seconds, so this has to be continually broken down in order to sustain any form of activity. When there isn’t enough oxygen to meet demand for the activity your are performing, the muscle cells make ATP without oxygen, or anaerobically.
In an endurance activity such as running, this results in the accumulation of lactic acid in the muscles. Lactic acid is removed, but if it is being produced at a faster rate than can be taken away, you cross what is known as the ‘lactate threshold’.
Regular running will push up the threshold point, improving your aerobic capacity, and taking you closer to your VO2 max. This will allow you to work at higher intensities.
As you become fitter, the number and size of mitochondria increases to cope with the higher demand for energy production. Like any muscle, the heart gets stronger when it is worked, and the amount of blood in your body increases, particularly the volume of red blood cells, which carry the oxygen.
Another bonus of regular aerobic training is that it teaches the body to use fat as its energy source, instead of carbohydrate. Regular running allows glycogen, the body’s stored form of carbohydrate, to be 'spared' or saved, and since we can only store a limited amount of glycogen, it is useful to be able to use fat as an alternative energy source.
So there you have it. Becoming a runner brings a whole host of positive health benefits that should be enough to convince you to get those shoes on now and get running.