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Default The importance of cardio
by MVP 03-09-2012, 02:20 AM

by Will "MVP" Riggs

Notes: My very first published article.

Cardiovascular exercise is the most unique in popularity of any type of exercise around. It's strange, because most weightlifters don't do it and most people that don't lift weights do do it. There are many forms of cardio, all have pros and cons. The most common type of cardio is HIIT (High Intensity Intervals). What this is, is a near constant change of cardio, because your body can adapt to it so quickly. You would do a 45 second jog and 15 second sprint for 8 minutes one day, then the next minute for 9 minutes, think of a cardio version of progressive overload here. After you reach about 10 minutes or so, you can switch it up to 30 seconds / 30 seconds and even sometimes change to 15 seconds / 45 seconds. The benefit of it is how it can increase your metabolic rate afterwords, therefore continuing to burn fat. The cons to this is it doesn't increase your aerobic capacity quite as well as a lower intensity cardio and due to the higher demand of energy, it could cost you more muscle.

There are three systems your body uses for it's energy requirements. The anaerobic glycosis (without oxygen) system that you use during resistance training, or at least during the contraction phases of resistance training, the aerobic (with oxygen) system which is the primary system for the body's energy requirements, and the creatine phosphagen system. You use your aerobic system because it delivers oxygen to your muscles, therefore keeping you going longer.

You use anaerobic to deprive oxygen and use ATP, your body only stores about 10-15 seconds of ATP at a time, which is a you fatigue so much quicker against resistance than just jogging. Another reason is because the byproduct of the anaerobic system is lactic acid. Your body uses glucose during the anaerobic system and when this falls short, it uses the creatine phosphagen system, which means when your anaerobic requirements falls short, your body runs out of quick ATP and breaks up creatine phosphate (which is a high energy molecule in the muscle cells that can be broken down to form ATP) as it's energy source. ATP converts to ADP when it is used, the "T" meaning "tri" and the "D" meaning "di". This is why the infamous supplement "creatine" gives you so much longer of a workout, when glucose can no longer be used anaerobically, creatine is then used to continue ATP production.

The aerobic system produces ATP inside of the mitochondria of the muscle, while the anaerobic system doesn't. The anaerobic system produces ATP outside of the mitochondria. The "aerobic" system - not only uses glucose but also uses fatty acids as a way to produce ATP. So regardless of what anyone says, you don't have to be in a calorie deficit to burn fat. But I'll get into that in another article. One of the main reasons glucose/glycogen cannot be used for long periods of time in the anaerobic system is the byproduct of the system, lactic acid, which calls for immediate soreness and faster fatigue.

There are three types of blood vessels in your body - capillaries, arteries and veins. Capillaries are smaller arteries, and are the site of nutrient and gas exchange. Arteries are the biggest of the three and send oxygenated blood away from the heart (the exception is the pulmonary artery that carries low oxygen) and veins send deoxygenated blood towards the heart (the exception is the pulmonary vein). These fall under two types of circulation that your body works in - systemic and pulmonary. Systemic circulation is the circulation of blood from the heart (coming from the left ventricle) that pumps to the entire body.

The left ventricle receives blood from the left atria through the mitral valve. The left and right ventricle pumps simultaneously, but left pumps with significantly greater force in order to send the blood to the rest of the body, while the right ventricle (the source of pulmonary circulation) sends blood to the lungs and back. During the systemic circulation, blood enters the left atria, then a fraction of a second later is pumped into the left ventricle and then during systole (the contraction phase of the cardiac cycle) it is pumped into the pulmonary artery, which sends the blood to the lungs where it reaches the capillaries and it gives away carbon dioxide and takes in oxygen, it then goes into the pulmonary vein to be sent to the left aria with it's fresh oxygen, then pumped into the right ventricle, then during systole is pumped into the aorta (which is the largest artery in the human body) that then sends this freshly oxygenated blood to the superior vena calva and the inferior vena calva.

So how does cardiovascular or "cardiopulmonary" exercise fall into this? Your stroke volume will increase and your resting heart rate will decrease (once you have trained your heart), so your cardiac output will stay the same (resting) yet increase during exercise and vigorous heart-rate. This means your stroke volume (the amount of blood that leaves each ventricle each time the heart contracts) will increase with a more efficient heart and your resting heart rate will decrease significantly. This is because when you exercise your heart aerobically, the inferior walls of the ventricles will increase, allowing more stroke volume and less work from the heart to deliver energy to your muscles (since there is minimal need for oxygen at the muscles during rest). Your heart improves in delivering oxygen to the muscles more efficiently. The ejection fraction also increases. Let's keep in mind that during the rest, your ejection fraction (the amount of blood that leaves the ventricles during systole) is about 50%. This is because there is minimal demand for energy at the muscles. When the demand for muscles significantly increases (during resistance training or aerobic training), the ejection fraction can increase to up to 100%. Therefore, so would the stroke volume and cardiac output.

Increasing your anaerobic and aerobic capacity at the same time - by doing something like HIIT, releases certain hormones that can increase heart rate like epinephrine and norepinephrine (of course with someone like beta blockers this wouldn't count, since beta blockers cancel the effects of the two hormones). It will also increase your metabolic rate and keep you burning fat. The problem with it is it can use muscle tissue with it's high demand of energy. A person with a lower metabolism would respond best from something like this. A person with a higher metabolism (metabolism is the rate your body uses it's energy) would be better using something like a lower intensity cardio - walking on an incline. A "talk test" is the general rule of thumb when performing such low intensity cardio. For someone going into a slow, gradual cut and with hopes to build muscle and / or strength at the same time, that has a higher metabolism, this is the ideal type of cardio you should consider. It would train mainly your aerobic system instead of both anaerobic and aerobic and therefore increase your endurance better than just doing something like HIIT.

When you perform exercise for your heart. The lungs ability to abstract and use oxygen increase, your hearts ability to deliver oxygen to the muscles aerobically increases. So therefore, instead of your heart having to beat faster in order to supply your body and muscles with oxygen, it will simply release more blood during the systolic phase of the cardiac cycle. Systole refers to the contraction phase of the cardiac cycle, while diastole refers to the relaxation phase. As mentioned earlier, the heart contracts simultaneously - yet the left ventricle contracts with a significantly greater amount of force. Both ventricles also release the same amount of blood, the ventricles (bottom chambers of the heart) are called the "power pumps" and the atriums are called the "primer pumps", which are the top 2 chambers of the heart. When stroke volume increases, resting heart rate decrease, yet maximal heart rate will always have the ability to increase, and exercising heart rate will decrease, giving you longer endurance and more efficient heart.

Why work your biceps over your heart and lungs that keep you alive?

Article Source: Benefits of Cardiovascular Exercise
Personal Trainer- ACE, NASM AFPA; Nutrition Consultant- AFPA

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