How Much Cardio Should I be Doing?

So, I’m going to start this off by defining cardio because a lot of people actually question if what they’re doing is considered cardio. And there is some science to it and I know not everyone likes science.. but I personally enjoy learning the science and research behind physiology because when you become educated on how the body works, you can again, make educated decisions about what is best for your body and your goals! So, hang in there as we get into some science so you can understand more than just ya know.. cardio is good for your heart and you're doing cardio if your heart rate is slightly elevated.


Basically, cardio is any form of exercise that increases the heart rate and is typically labeled aerobic. Now technically cardio and aerobic are two separate terms because cardio is a form of exercise that increases your heart rate.. aerobic simply means “in the presence of oxygen", meaning the work or exercise that your body is doing requires oxygen intake, transport, and utilization. So when you are doing a cardio workout, you are working aerobically. So, while they are technically different, they are basically synonymous right, because they occur simultaneously. You can’t have one without the other. If you’re heart rate is elevated because you’re doing cardio, it’s also aerobic because your body is utilizing oxygen for energy. So through this episode, just know that when I talk about cardio I’m also talking about aerobic exercises.



Now, Anaerobic means the opposite.. "in the absence of oxygen". So aerobic exercises, and we can use long distance running or jogging as an example, is a form of cardio which requires constant use of oxygen transport and utilization as well as a separate energy pathway than anaerobic or nonaerobic exercises (exercises like weight lifting, strength training, or short sprints) and aerobic exercise consistently challenges the heart and lungs. So let me stop there and get into a little more science.. just stick with me through this…


Your body has to receive energy during exercise, whether its aerobic or anaerobic.. and muscle cells have to use either ATP or adenosine triphosphate which is a form of stored energy used for muscle contractions (for something like a 1 rep max), glucose (for something like a sprint), or oxygen (for something like a run) to produce that energy. OK, so adenosine triphosphate (ATP) is a molecule that stores energy for when your muscles need it. It is the beginning energy source for all of our movements.. BUT the muscle cells only store a limited supply of that ATP and will need to be restored. And when ATP is maxed out your body has to utilize other sources of energy.


Now energy gets to the muscles via 3 different pathways in which your body transports this energy..


The first pathway is ATP/CP Pathway where phosphate bond energy is released to the muscles. All activities begin in this pathway of energy (the ATP/CP energy pathway). Now this pathway of energy is anaerobic meaning its not using oxygen for energy use. This is just for explosive type moves such as power lifting or a 1 rep max meaning you’re lifting super heavy for 1 rep, resting, and repeating.. Explosive strength/maximal effort, but short periods of time. This pathway is maxed out at 1.26 seconds so again, short bursts of energy. Then there needs to be enough rest time for ATP or energy to fully be restored. So this is not aerobic.. your heart rate may increase and your oxygen may increase but it’s for a very brief period.. not long enough to be considered aerobic or cardio.


So ATP/CP , what I just talked about, is the starting pathway for energy given to the muscles. Another non-aerobic pathway of energy is the Glycolytic pathway in which glucose is broken down to produce energy because the ATP was just maxed out.


At max conditions this pathway burns out a little under a minute and a half before the last pathway comes into play. That’s why it’s important for these semi-short burst of energy type moves to be fueled by carbs. You can think of doing a set of 10 reps during strength training where your heart rate may be up for a minute before you rest. Or think of a 40 second sprint or something. Semi-short bursts of energy.. So back to talking about carbs for instance, sprinters and weight lifters shouldn’t really be eating a no carb or low carb diet because your muscles need glucose for energy in these types of movements where your body is using the glycolytic pathway to give you energy.

That last energy pathway is the oxidative pathway which is what is utilized during aerobic exercising (activities you do to challenge the cardiovascular system) and this is what many people picture when they think of cardio, like running or cycling. Any energy exertion activity that lasts more than a couple of minutes starts using the oxidative pathway. So during a longer run, your muscles are receiving energy from the oxidative pathway as it is using oxygen to produce the energy your muscles require). So, these are longer activities with low to moderate intensity where your body is using oxygen to create energy.

So from this we can learn that cardiovascular fitness is your aerobic exercises where your body is using the oxidative pathway for energy, where your oxygen and heart rate both increase for a designated amount of time


OK, hope all of that makes sense!


Now, Cardio is short for cardiovascular, and cardiovascular fitness is essentially the ability of your heart and lungs to produce oxygen rich blood to your muscles allowing those muscles to then use that oxygen to produce energy for your movements.

So any exercise that gets your body in the state of using this oxidative pathway for energy can be considered cardio, right? And if you want to be aerobically fit, that essentially means that you want your cardiovascular system to be healthy and efficient. This entails many factors… heart rate, stroke volume, blood pressure, oxygen intake… and in order to make those things more efficient you have to train it!



Training takes time, but your body adapts very quickly in this realm. Your body will begin to adapt to the demands you place on it as you overload the oxygen transport system. So you overload the oxygen utilization system, and your body is like ok… we’re doing something new, let’s adapt.. and thus your heart and lungs get stronger and more efficient. It doesn’t take years or even months to notice changes in your cardiovascular health… People can train consistently for a pretty short period of time … even in just a few weeks.. and then fairly quickly notice a difference in their ability to not get winded going up stairs for instance. So the body will adapt and it will become more efficient at utilizing oxygen.


So, how do you know when you’re in that cardio state where you’re challenging your cardiovascular system or the heart and lungs?


There’s a couple of ways to do this and the first is by using your heart rate as an indicator. There’s something called the aerobic training threshold which is the minimum level of intensity or minimum heart rate that you have to get past in order to see significant changes in your aerobic fitness. Ideally, you want to be in an aerobic training zone which is a range of intensity to really improve your level of fitness. So, a general rule is that you subtract your age from 220. So I’m 33, that would be 187 .. that would be my max heart rate. And then the aerobic training zone would be 55-85 percent of that number , so at 55% of that my max heart rate would be 102 bpm and at the higher end my max would be 159. So to have any kind of improvement in my cardiovascular health I would want to see my heart rate up to between 102-159 bpm for a designated amount of time. Now don’t confuse this with thinking that heart rate is an indication of aerobic fitness… it’s just a byproduct of the process.. an external indication.


Another more simple external indicator is your ability or inability to hold a conversation. Ok, if you’re able to talk like normal and carry on a decent conversation, then I doubt you are in that aerobic zone. I move my body all the time and I’m able to carry on a conversation. I love taking walks with my kid. Walking has many benefits, but it doesn’t get me in that aerobic zone you see? So if your goal is to just simply increase your total daily energy expenditure or just to get some fresh air, then a light walk is awesome. I love doing that and it has many benefits for me. But it DOES NOT effect my aerobic fitness levels ok? It doesn’t get my heart rate up. For some it might… maybe someone who hasn’t exercised in years and sits all day every day, this might be the way to get their heart rate up. Or you know, if someone is extremely obese and can’t do any other type of aerobic exercise, this might be the way. But for me, there’s no real heart rate increase. To be in that aerobic zone, your heart rate and your speech will be an indication of when you have reached that zone.


Now, the time spent doing aerobic exercise is another issue. Some people will run for hours, some get it done in 20 minutes. It really comes down to what is your goal?!


There’s no one solid magic equation or indicator for a healthy cardiovascular system. Now we can look at what is recommended for our age and such but again, it all comes down to what do you want out of it.


If you want to be able to run a marathon 6 months from now, then 20 minutes a couple times a week is probably not gonna cut it right? But if you’re just looking to improve you overall health, that’s definitely better than doing nothing. A lot of people think if they’re not doing two hours 5 days a week, then they’re not getting anywhere, but research actually shows that anything more than 45 minutes at a time has a limited effect on improving your aerobic fitness levels. Yes, you’ll burn more calories but not necessarily increase your level of fitness.



Another concern is muscle. If you are wanting to maintain or build muscle, too much cardio can actually be counterproductive. You really don’t want to be going over more than 3 -30 minute cardio sessions if your goal is to maximize your lean muscle mass. So, those are just some things to note when you’re thinking about cardio.


So I’ve told you what cardio is. I’ve told you what it means to be in that cardio or aerobic zone and how to know if you’re there. And I’ve given you a bit of a short answer on how much you should do.. and the answer is.. it depends on your goals.


If you have a hefty goal to run long distances, then your cardio should be pretty intensive and frequent. If you’re simply looking to maintain or better your cardiovascular health, the CDC recommends 30 minute sessions 5 days a week or about 150 minutes a week, meaning you don’t have to do it in chunks of 30 minutes. BUT again, this is a guideline. Are you unhealthy if you don’t get 150 minutes of cardio in every single week? NO. Something is always better than nothing. I don’t just run on a treadmill… well ever really. I used to. If your goal is to build and maintain muscle, that 5x a week is going to hinder your progress because cardio is catabolic, meaning it breaks down. So it will begin to feed on the body to get the energy it requires and that could mean lean muscle loss.


It doesn’t look the same for everyone right? Just because I’m not jogging or doing HIIT several days a week does not mean that I’m not healthy or fit. So my advice is to do what you can, when you can, but don’t stress about getting hours of heavy cardio in unless your goal is long distance running or a triathlon or something like that.


So what about fat loss?!


I honestly don’t recommend cardio to my clients just for losing weight.


1. That’s miserable to try and outwork a bad diet…people often get in the mindset that they need to earn their food and that’s where this mindset of using cardio for fat loss gets a little unhealthy. I’ve been there where I would feel like I’m about to die after an hour of running just so I could have a “cheat meal.” I’m just telling you right now, I don’t recommend going down that road… it’s a hard one. It’s miserable, it’s frustrating, and it’s not very effective… which leads me to #2


2. It’s definitely not as effective as you may think in helping with fat loss. It’s a common misconception that cardio is the only or best way to lose fat and that’s far from the truth. Yes, cardio does burn calories during your workout, but if your goal is fat loss, stay away from trying to earn your calories ok? DO NOT eat those so-called extra calories you burned. That’s a trap! Because first of all, those trackers are not accurate at knowing how many calories you burned so you’re constantly going to be guessing. And second, food is not something that should be earned .. that’s a dangerous mindset. Your body deserves food just for existing. You need it for fuel, energy, and overall health. So stop looking at it as a reward to be earned or a mistake to be punished for.


3. Your time is much better spent focusing on a calorie deficit and weight training. A calorie deficit through manipulation of your calorie intake is the most efficient way to lose fat. If you eat less calories than you burned, science proves that you WILL lose FAT. The tricky part is in knowing how much your body is actually burning. But once you know, then you can work on your calorie intake goal.


Now, what kind of cardio is the best?


You probably already know what I’m going to say.. but there is no right or wrong answer here. It’s whatever you enjoy that gets your heart pumping and challenges your lungs. If you want to do cardio regularly, I suggest picking something that you enjoy. There’s a lot to choose from… rowing, cycling, running, boxing, dancing or Zumba, hiking, swimming, jump rope,… all of these are things that have the potential to get and keep you in that aerobic zone and you can change the intensity of any of these.


Let’s talk about some popular terms people use and which of them is actually aerobic versus anaerobic.


So one type is known as LISS (low intensity steady state cardio), meaning just what it says, it’s not intense, it’s steady pace, and you’re still in the cardio zone. This can be a light jog, walking fast uphill, a steady row or biking, you can make pretty much anything more or less intense. If you want to stay in the cardio zone but have a little more intensity, you can jog and have short bursts in intervals or just do a steady paced run.


Then you also have HIIT or high intensity interval training.. Which implies that you are doing intense exercises in intervals. And this is like an all out exertion of your energy in short bursts. So, this is actually considered anaerobic because it’s shorter bursts of energy ,followed by rest… not a steady pace of cardio. You might have heard of this and the term is called EPOC or excess post-exercise oxygen consumption.. simply put, your body is catching up and working to repay that oxygen debt that incurred through your intense bursts of energy.


But again, this is one of those things, like weight lifting, that will continue to burn calories after your workout because you are putting your body in an oxygen debt. So unlike, cardio where your burning all your calories during the session, HIIT is an afterburner. So HIIT is like 90% effort for around 15-30 seconds followed by a rest period of about 60 seconds so your energy levels can be restored and then repeated.


Alright guys, I know this was a long blog post but I hope it gave you some insight into how much and what type of cardio to do! My podcast episode goes into a little more depth if you're wanting even more knowledge on this topic!


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Bye for now,

Jess