Cardiovascular training (aka cardio) is not only about how much calories you can burn in a session. It is more about training or conditioning your heart, lungs, blood vessels, and how our body utilize the energy more efficiently.
In this article I will be covering the benefits of performing cardiovascular training and conditioning along with how our body utilize energy.
Increase Blood Volume with Least Effort
First objective of cardiovascular training is to improve our VO2. VO2 represents amount of oxygen we can take in and deliver to the muscles. Why is this important? During physical activity our body utilize oxygen to breakdown fat cells to produce energy source called ATP (adenosine triphosphate). Which means, more oxygen we can take in and deliver to the working muscles, the more energy is produced. When the VO2 level is low, the body cannot take in enough oxygen to deliver to the muscles, therefore, fatigue kicks in earlier than those who have higher VO2.
By conditioning your cardiovascular system, heart will also get stronger and efficient about sending more blood throughout our body in 1 pump. This is known as stroke volume. There is another terminology called cardiac output, which is amount of blood pumped out of heart per minute. With proper cardio training our body can have higher VO2, Stroke Volume, and Cardiac Output. By doing so our resting heartrate can be lower and still be able to send adequate amount of blood throughout the body.
Increase Capillary Density
Having a strong heart is great but what about blood vessels? With heart being able to send more blood per heartbeat, our blood vessel also needs to adapt by increasing in its diameter and creating new pathways (angiogenesis) to enable the delivery of higher volume of blood to the muscles. Imagine you have a street with a traffic jam. There are two possible solutions. One is to widen the road. Second is add new pathways to the destination. This is the adaptation that our body does by exercising on regular basis. Benefit of angiogenesis is not only to send more oxygen to the muscles but also removal of metabolites such as lactic acids and pyruvic acids.
Increase Number and Size of Mitochondria
Mitochondria is the organelle that is responsible for the energy production. With a system called Kreb cycle and electron transport chain, mitochondria can create energy from glucose and fat. By performing cardiovascular training on regular basis, mitochondria will go through adaptation by increase in its size and its number, which means they can create more energy to the muscle.
Increase Lactate Threshold
Another adaptation by performing cardiovascular training is increase in lactate threshold. This is dependent on intensity of training. As we get fitter and able to use more oxygen efficiently, our body can rely on using fat as energy source and sparring glycogen. This process is called glycogen sparring. Higher intensity training requires us to use glycogen as energy source which leads to production of lactic acid. Through adaptation to cardiovascular training, the body has capability to utilize lactic acid as energy source and may be able to perform same intensity level without producing significant amount of lactic acid.
When you work out for the first time, you’ve gone through muscle soreness. But after a while, the same intensity of workout may no longer causes you to fatigue and able to handle higher intensity training. This adaptation is same for cardiovascular system. This adaptation may become helpful when you go through stressful situations, whether physical or psychological.
Improve Mitochondria Respiration
Mitochondria respiration refers to how mitochondria produce energy from fat and glucose for our daily performance. We have two energy sources that can be converted into energy, fatty acid, and glucose. Glucose will convert into two molecules called pyruvate and lactate.
Ideal primary energy source is fat. Stored fat or triglyceride can break up into 3 fatty acids and glycerol by the enzyme called hormone sensitive lipase (HSL). Fatty acid, then, with a help of the amino acid called carnitine, it enters mitochondria through the CPT1 transporter. Once the fatty acid enters the mitochondria, the process called Beta-Oxidation starts. This is the process where mitochondria further break down into acetyl-CoA. After the breakdown into acetyl-CoA then enters the last phase called Kreb cycle then to electron transport. Through this process mitochondria can generate 129 ATP from fatty acid.
Glucose has 2 pathways. First pathway is glucose breakdown to pyruvate through a process called glycolysis, then enter mitochondria convert into acetyl-CoA then enter Kreb cycle and electron transport like fatty acids. This process creates 32 ATP.
As we exercise, regardless of how fit you are, energy demand will increase. We do normally produce some amount of lactate, however, as energy demand increases, we create more lactate through glucose. Therefore, the second pathway for glucose is after broken down to pyruvate with decrease in cellular oxygen, then convert into lactate. If there’s enough MCT1 transporters in mitochondria, the lactate enters mitochondria then convert back to pyruvate. Pyruvate converts into acetyl-CoA and enters Kreb cycle and electron transport. In this process 32 ATP is created. You may see 2 ATP is created; however, studies have shown that even with lactate pathways can generate 32 ATP.
It is confusing but analogy I use is exchanging foreign currency. The body cannot use fat or glucose as energy just as it is. Therefore, mitochondria help exchange them into currency called ATP so that body can use them. Exchange rate of fat is higher than the glucose, but the process takes more steps than exchanging glucose into ATP. Therefore, when performing exercises that require fast movement or lifting heavy weights, the body prefers glucose for it is faster energy source.
Consequence of Training Randomly
Biggest issue that I see with people who are starting to train or coming back to training from injury or busy schedule, they focus more on how much calories they can burn off per session to make up for the lost time.
This can become counterproductive because, the body need to be trained or retrained to metabolize fatty acid as energy source to metabolize fat. Which means we are required to train in lower intensity for majority of the time to help recreate transporter in the mitochondria to bring in more fatty acid to convert them into energy. Training in higher intensity will only allow you to use more glucose and not much of fat. When you have not been training, you will need to train the body at appropriate intensity.
Here is another problem. As mentioned earlier, when the physical exertion gets higher the body will produce lactic acid. People who have been trained at and above lactate threshold may be able to utilize lactate as energy source. However, if you have never trained or have not been training in lactate threshold intensity level, chances are there will be production of lactic acid in an amount that the individual may not be fit enough to handle. Lactic acid will breakdown into lactate and hydrogen ion (H+). Lactate itself can be source of energy if the person has been trained in that intensity level. If not, the lactate will send into the blood stream along with the hydrogen ion, which is acidic.
Complication comes when people assume they had great workout and deserve wine, beer, energy drinks, coffee, sugary food. Along with lactate and hydrogen ion, these are all low in pH level which means acidic that can lower the blood pH level. Normally body will work to bring back the blood pH level through hydration, proper nutrition, and sleep, however, when low blood pH level continues, the body can go into condition called metabolic acidosis where blood pH level gets below 7.35. Symptoms of metabolic acidosis can be fatigue, accelerate heartbeat (tachycardia), dizziness, loss of appetite, shortness of breath, headache and so on. Commonly, this condition is for those who have kidney issues but can’t rule out the possibility of training and dieting in a wrong manner, which may have potential to cause the similar condition.
Ideal Cardio and Conditioning
There are so many different ways of training cardio. Majority of time people assume it is just done with walking, jogging, and bike. However, sled push, step ups, ball slams, kettlebell, dumbbell, barbell exercises can all be utilized in cardio and conditioning training program.
Each program should be mindful of what energy system you are wanting to use. If fat usage is your goal then you want routines that is challenging enough but able to sustain for at least 2 minutes, ideally 10 minutes or more. If you want to train your lactate threshold or use glucose as energy source, it is easier when you incorporate heavier weight. During the session, you also want to plan the recovery time per each set to make sure your heartrate can recover fast, ideally 1-2 minutes to drop 20-30 beats from the peak performance heartrate.
To monitor your exercise intensity level, monitoring your heartrate is useful. For fat utilization target 180 minus your age. So if you are 50 years old, your target heart rate for fat usage would be 130bpm (beats per minute). Since it is difficult to sustain heart rate, I usually give 10 beats range from calculated heartrate so 130-140bpm for someone who is 50 years old. For lactate training, I would add 20 beats on 140 bpm. Therefore the range will be 140-160bpm for someone who is 50 year old. Yes, it is estimated number and it is a guide. If you want the accurate number you may want to invest in active metabolic testing or purchasing a device called Morpheus Training System.
Cardiovascular training or conditioning is not just about burning extra calories. That may be there too. However, what is more important is training your heart, lungs, and efficiency of energy usage so you can perform better and recover efficiently.
Kota Shimada
コメント