There has been interesting discussion happening in social media regarding cardio workout. Question that has been rise is “is cardio workout important?”. This is not an easy question to answer, and my answer is “it depends”. First, we need to understand what cardio workout means and what is the purpose behind it. Then, we can think in terms of what method should we use for different cases.
Cardio work itself means “heart”. You may have heard the terminology cardiovascular system, which means system that includes heart and blood vessels. Proper term for cardio workout is cardiovascular training. So, what is being accomplished by training our heart and blood vessels? There are several criteria that needs to be looked at.
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 acids. Through adaptation to cardiovascular training, the body has capability to increase lactate threshold.
If you every workout for the first time, you’ve gone through muscle soreness. But after a while, same intensity of workout no longer causes you to fatigue and able to handle higher intensity training. This is adaptation of cardiovascular system and have increase in lactate threshold.
Energy System
There are three energy system that we need to be aware of. They are ATP+CP, glycolysis-lactate, and aerobic system. Depending on what training method you use, what you will accomplish will be different.
ATP+CP system is very short in duration, however, high in intensity. Duration of this system is from 1-20 seconds and considered anaerobic. Some of the examples can be lifting 1 - 5 repetitions @ 85-100% of 1 RM (rep max) and sprints. Because of the short duration, body has no time to use glycogen or fat as energy source. Energy source will come from already stored ATP and creatine for immediate energy.
Glycolysis-lactate system is duration of 20-120 seconds and classified as anaerobic. Some examples might be higher repetitions (10-20 reps) of strength exercise, short run, high intensity interval training, and so on. Because of longer duration body will utilize muscle glycogen and lactic acid as energy source.
Aerobic system is the third system and can use both muscle glycogen, lactic acids and fatty acids depending on the intensity level. Duration can be from 120 seconds to 10 minutes or longer. This can be run, bike ride, jump rope, sled push, hike, swim and so on.
How Should We Implement Cardiovascular Training
To improve cardiovascular system all three energy system should be trained. However, cardiovascular training does not need to be just walking, running, rowing, biking, swimming though they are simpler (not easy) methods of cardiovascular training.
Although ATP+CP system requires us to train at higher intensity level, however, higher intensity is relative to your capability. For example, if you are using walking as method of cardiovascular training, you may be able to get into ATP+CP system by walking faster. For some people it may be lifting heavier weight. So, intensity level is relative to your capability.
How often you should train in each energy system may be the next question. This is depending on how well your body can recover from training in those energy system. Basic system would be aerobic system where you are training the body to utilize fat as energy source and should be the highest frequency training within those 3 systems. Why is this important. Let’s say for example that some weighs 150lb and have a body fat percentage of 15%. Which means this person has body fat mass of 22.5lb (10.2kg). Because 1g of fat is equal to 9 calories 22.5lb fat will be equal to over 90,000 calories! Training more frequently in aerobic system is important because we can train our body to utilize huge energy source that is stored in our body. This would be beneficial not only for those who are wanting to lose fat but also an athlete wanting to have more endurance in their sports.
In muscular growth, for strength or size, we have a saying weak muscle cannot grow. In other words, lifting lighter weight alone cannot grow muscles and occasional heavy weightlifting becomes important. This is also true with cardiovascular training. This is where ATP+CP and glycolysis-lactate energy system becomes critical part of cardiovascular training to strengthen the heart and blood vessels. However, just like you shouldn’t lift heavy every training session, ATP+CP and glycolysis-lactate training shouldn’t be done every session as well, because the body may not recover properly. For glycolysis-lactate training you should be training once per week and for ATP+CP training should be done once to twice per month.
By carefully planning your cardiovascular training, in few months, body can utilize our body fat as energy source at higher intensity level. Randomly sprinting on bike, jogging for 60 minutes, walking at slow speed alone is not very effective. Just like strength training you will need to plan cardiovascular training. Good news is it is possible to plan the strength training and cardiovascular training at the same time.
Purpose of Cardiovascular Training
To answer the question of purpose behind cardiovascular training is not how much calories we can burn in one session. It is to improve our cardiovascular system and efficiency of fat utilization by increasing capillary density, increase in size and number of mitochondria, and increase in lactate thresholds.
If you are not sure of where to start, start by walking 15-20 minutes for 5 day per week at the pace of where you can have a conversation if you are walking with friends. Then 1-2 days of those 5 days, you can walk same duration but with 3-4 sets of 1 minute speed walk with 2-3 minutes easy walk in between sets. This pace may be fast enough to feel some fatigue in your legs but able to still have conversation but may be challenging.
Cardiovascular training aka cardio is critical part of training program for anybody who wants to be fit and strong but needs to be structured according to the individual capabilities. Cardio does not have to be just steady state, in fact it is more beneficial when it is not. You can also implement strength training as a part of cardiovascular training. Nutrition will also play important role in ideal performance during training and recovery from training.
Kota Shimada
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