Breathing Too Much (and too little)
But back to our dinosaur moment. As we run to get away we take in huge gulps of air to help oxygenate the muscles working to save our life. If you’ve played the hyperventilation game at school, where you take ten or twenty deep, rapid breaths and try to stay on your feet, you know that the moment you take in more oxygen than you need, you get light-headed and flushed and you could even pass out.
The body is designed to avoid that. How fast we breathe normally is the direct result of chemoreceptors found in our main arteries. They monitor the oxygen and carbon dioxide levels in our blood and tell us whether we need to breathe faster (to get more oxygen in) or slower (like when we are asleep and don’t need that much).
So the amount of oxygen found in the blood is closely related to fitness levels and exercise. When our muscles work hard they need oxygen to help convert glycogen and stored fat into energy. As a result oxygen levels in the bloodstream drop. The chemoreceptors spot that and signal the brain to let the intercostal muscles work harder and we take more breaths and we start to breathe harder.
Now, breathing hard is normal every time we run for our life or do some physical exercise. Being out of breath however is not. The amount of oxygen we can get into our bloodstream when we push our bodies hard is determined by two factors: the ability of our body to absorb oxygen and the ability of our body to distribute that oxygen where it’s needed.
The first one depends on genetics and though hard exercise, regular Velociraptor runs and HIIT training will help with some overall improvement this will be marginal. To go back to our balloon analogy, the size of the balloon that gets filled with air inside your chest, what we usually call “aerobic capacity” is determined by your DNA. Training may help you achieve a few small gains by making the lungs stretch regularly but this will not make much difference.
Which brings us to the second factor: your body’s delivery system. If the balloon inside your chest is half the size of someone else’s and they’re running beside you to escape the Velociraptor, the only way to get the same amount of oxygen to your muscles as they do, so you don’t get caught, is to breathe twice as fast.
The speed at which oxygen is absorbed from the lungs into the bloodstream and then gets transported to the muscles that need it most depends on the cardiovascular system and this you can really improve with training. The rate at which the oxygen is transported to the muscles is usually measured as litres of oxygen per minute and it’s known as VO2 max.
When the oxygen demands being made by our muscles exceed our ability to breathe in enough oxygen, our VO2 max is outstripped and we experience fatigue, dizziness and the dreaded stabbing pain of the side stitch that runners get on the right side of the body (usually) or the tip of the shoulder blade. At that point we get out of breath, we start gasping and the Velociraptor gets a meal.
It is clear then that the higher our VO2 max is the fitter we are and the harder we can physically work our bodies.
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