There are two main types of exercise that you can do: resistance training and cardiovascular training. There are great differences in how to train for each and how your body adapts to each one. In this article, we will break down cardiovascular exercise so that you know everything you need to know about how to do it, why to do it, and when to do it. The information you find here will be a broken-down version from the National Strength & Conditioning Association’s book Essential’s of Strength Training and Conditioning.

 

How do we actually get better at cardio?

The process through which we improve our endurance is much different than how we build muscle. I’ll give you a quick spoiler: it has nothing to do with your lungs. In fact, our lungs really have no possible way that they could adapt. There are two main adaptations that occur that we will talk about. These include adaptations of your heart and changes in how your body fuels exercise.  

 

How your heart changes

The biggest key to having a better cardiovascular capacity is making your body better able to deliver oxygen to your muscles. Delivering oxygen throughout your body is really your heart’s main job when you exercise. So, what your heart needs to do is be able to deliver more oxygen to your body.

The way your body delivers oxygen to your tissues is in through your blood cells. So, there are two ways that your heart can go about improving oxygen delivery: increasing heart rate or increasing the amount of blood that is pumped with each beat of your heart. Increasing your heart rate is the much more immediate way to improve oxygen delivery, and it is what you experience when you begin any type of exercise. However, there is a maximum number of times that our heart can beat every minute and no real way to improve above that number. As a result, your heart must be able to pump more blood with every heartbeat.

Essentially, the chambers in our heart that hold and then pump the blood into our body stretch out as we work on our cardio. This means that every time your heart beats, more blood is being pumped into circulation. There are many factors that cause your heart to stretch in this way. Although, the basic reason why is this: when we exercise and our heart rate increases, there is a lot more blood flowing in and out of our heart. The force of the blood coming in and continuously pushing up against the walls of your heart cause it to stretch out over time.

If you are taking part in endurance training, there are a few changes that you should notice in your body over time; and they all are a result of your heart being more efficient:

 

1)    Your resting heart rate will be lower.

• When we are at rest, we only need a certain amount of oxygen to fuel our body’s function. If each heart beat is delivering more oxygen, then we don’t need as many heart beats to provide our bodies with that amount.

2)    Your heart rate at any given intensity will also be lower.

• Let’s say for example’s sake that when you first started training your heart rate at the end of a 1 mile run was 150 beats per minute (bpm). If you have been following a program for about a month, you might notice that your heart rate after a 1 mile run would then be between 130-140 bpm. This is for the same reason as before, if each beat produces more oxygen, then we don’t need as many beats per minute. You might also notice that this distance and intensity will feel easier as a result.

3)    You will be able to perform much more work at your max heart rate.

• Now, exercising at your maximum heart rate is probably not something you should do very often as this is a very high intensity level. However, there is a cap in how many times your heart can beat in a minute. If each heartbeat is providing more oxygen, then what you are able to do at that cap will be much greater.

 

Changes in how we fuel exercise

This is the second adaptation that can really make a difference. What basically happens is that your body is able to start using fats for fuel earlier on in exercise as opposed to carbohydrates. Now, allow me to explain why that is important.

If someone who is completely untrained went for a run, their bodies would probably be getting near 100% of their energy from their stored carbohydrates at the start of their run. However, if a conditioned athlete went for the same run, then they may likely be deriving 50% of their energy from carbohydrates and 50% from stored fats. This is a problem for the untrained runner because depleting our stored carbohydrate is a sign of true exhaustion. Therefore, if the conditioned athlete is using fats for energy earlier on, then their carbohydrate stores will last longer and it will take them longer to hit exhaustion.

Our bodies generally prefer to use carbohydrates for exercise because most of the carbs stored in our bodies are stored in our muscles. This makes it very convenient for your working muscles to access them. However, our stores of carbohydrate are limited and our stores of fats are seemingly unlimited in terms of their use for exercise. Once our bodies are better able to use fats earlier on in exercise, the longer it will take until we fatigue.

The mechanism by which this happen can be complex. However, a basic summation can be described as follows. The enzymes that convert fats to energy are produced earlier on and the fats themselves are transported to your muscles earlier on.

 

Does it matter what kind of cardio you do?

The answer to this is similar to the answer in most things in this space: it depends. If you are performing cardio with the sole goal of improving your cardiovascular health and general endurance, then it probably does not matter too much and you should just do whatever type you enjoy. If you are training for a specific race like a marathon, triathlon, etc., then you should train for the sport that is relevant to you. The more specific your training is to your sport, the greater the transfer in performance will be to competition.

Another reason you might be working on your cardiovascular capacity is to establish an aerobic base. An aerobic base is a fancy word that describes a base level of cardiovascular fitness that all athletes should have. How high level of fitness this base is will depend on what type of athlete you are. However, let’s talk about if you primarily go to the gym and lift weights recreationally. If your goal is to grow muscle, then resistance exercise, such as weight lifting, is what you should spend 90% of your time doing. However, spending some time to maintain a decent bit of endurance can make your weight lifting much more efficient. Primarily in the sense of making you recover in between sets and in between workout sessions. If this is the reason that you are working on your cardio, then again, it likely does not matter too much what kind you do.

 

What health benefits can you expect from cardio?

The health benefits from exercise are much vaster than most people realize; it truly cannot be understated how important it is to get stronger and improve your endurance. For a detailed description on how strength training can improve your health, you can read more on that here. However, let’s chat about how cardio might help you. Here is a short list of the benefits you can expect to gain:

• Decreased blood pressure

• Decreased heart rate

• Decreased cholesterol

• Decreased LDL

• Increased HDL

• Decreased risk of heart attack or stroke

• Decreased risk of diabetes and insulin resistance

• Improved cognition and mental health

• Decreased risk of Alzheimer’s disease, Parkinson’s disease, etc.

• And plenty more that would take up the rest of this article if I listed them all

Another key point is that measures of health tend to increase as your fitness increases. Bottom line is this: exercise is arguably the cheapest, most accessible, and most effective way to improve your health.

 

Body Composition: will cardio help you burn fat and build muscle?

This is the one area where working on your cardio falls a little short. For a detailed description on how to choose exercise for body composition, you can read more about that here. As far as building muscle, cardiovascular exercise is not the best way to go. In order to build muscle, you need to get stronger; whereas improving your endurance is about becoming more efficient and not about getting stronger. Therefore, if your goal is to build muscle, it is best to stick with resistance training. For burning fat, cardio can definitely help, however there are better options as far as exercise goes. Again, resistance training tends to win out here over cardio. The reason being is that it promotes growth and maintenance of muscle mass (which helps you to lose fat specifically) and it will increase your resting metabolic rate as you recover from each session.

Here’s the bottom line, if body composition is the objective, then resistance training is the better way to go over cardio.