The science of how running impacts on the body is outlined below, taking in matters such as cardiac output, VO2 max, lactate threshold, and then we outline some other general benefits of running, should you need further reasons to take up running.
When you take part in regular running your body should experience the following:
Improved cardiac output
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.
Resting heart rate falls
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.
Improved blood supply
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 oxygen 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 fibre while a well-trained runner might have five to seven per fibre. The maximum rate at which oxygen can be extracted and used by the muscle is the VO2 max. VO2 is partly determined by gender (women have a lower VO2 max than men) genetics and age, but it will improve with regular running.
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, the muscle cells make ATP without oxygen, or anaerobically.
Improved lactate threshold
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.
Using fat as energy source
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.
If you’ve managed to take all the science on board then here is a quick list of some of the other general health and fitness benefits you may experience as runner:
Good for your heart
A consistent period of training will, as we have outlined earlier, mean you have a much lower resting heart rate than you had before you started out. It will also produce improvements in your respiratory system, meaning your blood will circulate more efficiently around the body.
Helps with weight control
The more you partake in running, then the more efficient your sweat rate becomes, and the greater your chance of losing weight. This is particularly the case if your runs are of a long duration and they are frequent throughout the week.
Helps reduce stress levels
If you have high stress levels, then running can really help. Running is a great way to get away from the stresses of the day, and what's more, it helps rid the body of the stress-related adrenaline that has been produced in the course of the day.
Reinvigorates your body
Running is beneficial if you have a job that means you are sat down all day or is not very physical. The exercise will also ensure that your body is reinvigorated after being largely stationary throughout the working day. Running can also help keep your cholesterol levels down. 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.