Updated 4th October 2023

Cardio exercise: How much do you really need?

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    Not all of us want to go to the gym 5 times a week. But what if there was a way to do quick, high-intensity, 20-second exercises and still reap benefits — or does that sound too good to be true?

    Prof. Javier Gonzalez and Jonathan break this down by looking at recent studies with male and female volunteers.

    They discuss how to optimize exercise routines to achieve the desired health benefits, taking into account factors like intensity, duration, and frequency, as well as the effect of working from home vs. commuting to the office.

    In today’s short episode of ZOE Science & Nutrition, Jonathan and Javier ask: How much exercise do we really need?

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    Episode transcripts are available here.

    Is there a nutrition topic you’d like us to explore? Email us at podcast@joinzoe.com, and we’ll do our best to cover it.

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    [00:00:00] Jonathan Wolf: Hello, and welcome to ZOE Shorts, the bite-sized podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf, and today I'm joined by Professor Javier Gonzalez, a professor and world expert on nutrition and exercise. And today's subject is cardio exercise.

    [00:00:18] Javier Gonzalez: Now most of us know that we need to exercise regularly to get health benefits. But it's often hard to work out exactly what sort of workout and how much of it we should be doing. We're often inundated with different methods and formats like hit training, endurance, circuit training, and even Zumba. And each one of these promises, certain improvements to our health.

    So the whole thing can get quite confusing.

    [00:00:47] Jonathan Wolf: And what we really want to know is which one of these is best and is it better to stop one of them in favour of another?

    [00:00:53] Javier Gonzalez: Well, that's the million dollar question and luckily there's some great research we can call upon to help us answer it.

    [00:01:01] Jonathan Wolf: Okay, then let's get moving.

    Hi, I hope you're enjoying the show and learning a lot. If you're not already a regular listener, I hope you feel like you might come back. If so, make sure to hit the follow button so you know whenever a new episode arrives. We release each week ad-free as part of our mission to improve the health of millions.

    And to help us, I'd love for you to share this episode with one person you think could really benefit from it. And of course to hit that subscribe button. Thank you, and enjoy the show.

    So, Javier, I was talking to a friend the other day who wants to do more exercise, something that I'm sure many of our listeners are familiar with.

    My friend, she's a busy working mother and she's finding it really hard to figure out what would give her the best bang for her buck. And as you said a minute ago, she was looking at all sorts of different types of exercise classes that she was discussing with me, hit classes, Zumba, yoga, you know, to name the three that I remember.

    And she was telling me that she's specifically interested in cardio exercise. Now, before we go any further, I hear this word cardio used a lot, but I'll be honest, I don't really understand exactly what it means. Can you explain it?

    [00:02:10] Javier Gonzalez: Yeah, so I think we should perhaps firstly address what isn't considered cardio, and that would be things like strength-type activities, things like weightlifting.

    And these activities are sometimes called anaerobic activities. And that word means your body is generally creating movement without using oxygen.

    [00:02:31] Jonathan Wolf: Alright, so Javier, uh, so far it's getting more complex, not, yes. What does this mean to say not using oxygen? Because I know that when I'm weightlifting like I am still breathing and if I stop breathing, I'm in, I'm in trouble fast.

    [00:02:43] Javier Gonzalez: Yeah. So our muscles can produce force and movement using different energy pathways. Some of these pathways require oxygen. And others don't. And when we're doing this strength exercise, we are mainly using the pathways that don't necessarily need oxygen. But the downside to these pathways is that we can only use them for very short bursts of activity.

    [00:03:05] Jonathan Wolf: Got it. And so, I guess if strength isn't using oxygen, then cardio exercise is where I am using oxygen?

    [00:03:13] Javier Gonzalez: Yes, That's right. Cardio exercise is generally called aerobic exercise. Anything like jogging, hiking, and most team sports have a big aerobic component to them. And these types of activities are utilizing your cardiovascular and cardiorespiratory systems.

    These are the systems responsible for drawing oxygen into your lungs, through your blood and into your muscles.

    [00:03:39] Jonathan Wolf: Now, Javier, help me to understand this a bit more. When someone does an activity like weightlifting or strength training, the effects can be quite noticeable, right? Their muscles may be getting bigger, their body shape may be changing, but with cardio, would I be likely to see results like this?

    Is that what you're aiming for?  

    [00:03:58] Javier Gonzalez: Not really, you may get some of those same effects, but the main benefits of aerobic exercise are more internal. And put simply, you are improving the capacity of your heart and your muscles to utilize oxygen. And the best way we measure this is something called VO2 max.

    [00:04:16] Jonathan Wolf: Okay, so we're getting a little bit geeky, which I partly love, but also I always want to make sure I understand. What is VO2 max? And what does it tell you, Javier? And you're a professor, so what, what would it tell me?  

    [00:04:30] Javier Gonzalez: Yeah. So let me get a little bit technical for a second, but then I'll bring it back to the, the basics. It's going to be worth it.

    So VO2 max is the maximum amount of oxygen that an individual can use during intense or maximal exercise. So the higher your VO2 max, the better your cardiovascular and cardiorespiratory systems are functioning.  

    [00:04:51] Jonathan Wolf: Got it. So I'm thinking a bit like in the olden days when you used to buy a car and they'd like tell you how fast you can go from zero to 60.

    It's sort of like this measure of your peak performance. And so you're saying it's sort of this, how much oxygen I can use during exercise and so therefore, I guess practically speaking, like how well my heart and lungs are working. Is that, is that right Javier?

    Exactly. Yeah.

    So what is considered a good VO2 max?

    [00:05:21] Javier Gonzalez: So it varies depending on age, gender, and of course the amount of physical activity that we do. And for someone like me, a good VO2 max might be somewhere between 44 and 51. And this number is the millilitres of oxygen that I would use per kilogram of my body weight in one minute.  

    [00:05:41] Jonathan Wolf: So looking at your Javier, if you are 44 to 51, I'm guessing I'm probably 10.

    So how important is it to have a good VO2 max? Or maybe if you can't, um, measure that, like how important is it to have this good cardio fitness? When someone is listening to this and they're probably thinking about their overall health, right? They would like to live more years of healthy life.  

    [00:06:06] Javier Gonzalez: Well it's absolutely crucial, Jonathan.

    It actually turns out that the level of someone's cardio respiratory fitness is a very strong indicator of how at risk they are of getting certain cardiovascular diseases and also overall mortality.  

    [00:06:54] Jonathan Wolf: So, just to make sure I've got that, what you're saying is that someone's cardio fitness level can predict not just their risk of heart disease. And I think listening to that, there's a certain logic, like your heart is sort of a muscle and, or you sort of have that thing, but you are also saying it's their risk of dying from anything.

    And then amazingly, this sort of cardio fitness level is actually like a more reliable, uh, thing than their weight, whether they smoke, you know, even if they have type two diabetes to predict whether someone is, is going to die.  

    [00:07:21] Javier Gonzalez: Yes, that that's right. Compared to all of these, cardiorespiratory fitness is an often overlooked measure from a clinical perspective.

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    [00:07:29] Jonathan Wolf: So that's amazing and um, it's part of why we're so pleased to have you here on the show. So I guess that means it's quite obvious that improving our cardio fitness is really important, uh, if we want to avoid those sort of cardiovascular problems, you know, the heart and stroke and things like that, but just prolonging our lives in general.

    So I guess what I really want to know is how can we design our exercise routines to have the best chance of boosting the health of that cardio system? And. Also being realistic, right? We all lead busy lives. There are lots of people like me who don't really love doing exercise. It's more something they do 'cause they feel that it, it's for their health.

    And if we go back to my friend who I was telling you about, right? She's really busy. Um, she has young kids. So she's really interested actually in sort of how little exercise is gonna be enough for her to get these health benefits.  

    [00:08:20] Javier Gonzalez: Yeah. So first of all, it's important to say that when it comes to cardio and and exercise in general, anything is better than nothing and more is better than less.

    But if people have limited time to exercise and they want to try and get the very most out of the time that they have, then there are three main things we can look at to optimize the health benefits of exercise. These are intensity, duration, and frequency.  

    [00:08:46] Jonathan Wolf: Ok, so we are getting a bit complicated again. So do our listeners need to use like a mathematical formula for these things to figure out like exactly how to work out?

    [00:08:55] Javier Gonzalez: No, they don't need a mathematical formula. Let me take you through some of the studies that have compared different types of exercise to help you understand how these factors work together. We can start with a review from 2015 in the Journal of Sports Medicine. They compare the health effects of people doing high-intensity interval training to people doing more classical endurance or prolonged continuous training.

    [00:09:19] Jonathan Wolf: And Javier, I keep asking these questions. What's the difference between those two types of exercise?  

    [00:09:23] Javier Gonzalez: So, high-intensity interval training has become very popular recently. It involves short, quick bouts of high-intensity exercise, one after the other with short rest periods in between. So that might be one or two minutes of exercise, and then another one or two minutes of rest in between those repeated bouts.

    Whereas endurance training is of a lower intensity overall, but it's more prolonged. So a 30-minute. Continuous jog or continuous bike ride for example. And this is sometimes thought of as the more traditional method of cardio.  

    [00:10:01] Jonathan Wolf: Alright, so that's really interesting 'cause the second one, they're clearly spending way more time exercising, right, than in the first with all the gaps.

    So it seems obvious that the one with longer time is gonna be better. What did the researchers find out when they compared these two?  

    [00:10:14] Javier Gonzalez: Well, interestingly, both types of exercise elicited large improvements in the VO2 max of healthy young to middle-aged adults. But actually, the gains in VO2 max were greater with the high-intensity interval training compared with the more classical endurance training.

    [00:10:33] Jonathan Wolf: So just to make sure I got that, you are saying that the high-intensity exercise, even though actually it had a lot more gaps in it, actually improved the participant's cardio fitness more than when they're just like literally nonstop for the full 30 minutes doing the endurance training.

    [00:10:49] Javier Gonzalez: Yes, exactly.

    And we know that exercise intensity can act as a replacement for exercise duration. It's a bit of a trade-off. So if the intensity of the sessions is very high, then less time is needed to obtain some of these health benefits.  

    [00:11:04] Jonathan Wolf: So I think I'm finally starting to understand why my trainer likes me to do something that wipes me out in 30 seconds, which always feels really unpleasant.

    Um, and it feels like we're getting a bit closer to the answer to our question?

    [00:11:15] Javier Gonzalez: Yeah. So if we really want to know what the absolute minimum amount of time needed to get a benefit from exercise is, then one study has shown as little as 6 X 10 to 20 second sprints per week, so that's just six sprints per week with some lower intensity activity just as a warmup and a cool down has been shown to improve fitness by almost 10% within two months,  

    [00:11:40] Jonathan Wolf: 10% just with like six, 10 second runs. That's totally crazy. That's like two minutes of exercise a week.


    So this information is definitely useful for anyone who is time-pressed. Um, and our team did some research, um, before this podcast and, um, what they found is that 80% of Americans do not achieve the CDC's exercise guideline, which is for at least 150 minutes of moderate-intensity aerobic exercise every week.

    But I think what you are saying is they could increase the intensity of the exercise and actually get away with doing a lot less than 150 minutes. Is that right?  

    [00:12:20] Javier Gonzalez: Yeah, these recent studies would suggest that would work. Yeah.  

    [00:12:23] Jonathan Wolf: So that's amazing and exciting, I think for anybody who's, who's really struggling with the time.

    But what about if I really don't like doing these intense bursts of exercise? Or maybe physically, I, I can't, right? Lots of people may be listening to this who have, have restrictions, but maybe I do have a bit more time on my hands, like, what should I do?  

    [00:12:41] Javier Gonzalez: So if the intensity is lower, then the duration needs to be longer.

    And even very low-intensity activity has been shown to have a number of health benefits. And something just like fidgeting might even be enough. A recent study showed that just lifting your heel off the floor repeatedly whilst you're sitting down in your chair, just like you and I now can lower the rise in blood sugar after meals by as much as 50%.

    And one thing to bear in mind with intensity and time is that. For the longer-term changes in your health, a certain amount of intensity is probably needed, whereas low-intensity exercise gets you some of these immediate effects on metabolism, albeit not as long-lasting.  

    [00:13:23] Jonathan Wolf: Amazing. So you've told me that I can either do a quite small number of short bursts of exercise like this, like 10 to 20-second sprints, six times a week, or I can do a lower intensity exercise for longer.

    How often do I need to do that? Is it every day, you know, a few times per week?  

    [00:13:41] Javier Gonzalez: Well, we have an interesting study that looked at links between the amounts and the intensity of exercise and cardiovascular mortality in nearly 4,000 people. These people were aged 40 years and over and were based in the US and these were all volunteers who didn't have cardiovascular disease when they entered the study.

    They wore a type of tracker called an accelerometer for a week, which is a device that measures movement.   

    [00:14:07] Jonathan Wolf: And Javier, is this a bit like a fitness tracker or a smartwatch?  

    [00:14:10] Javier Gonzalez: Yes, it is very similar.  

    [00:14:12] Jonathan Wolf: And so what did the study find?  

    [00:14:13] Javier Gonzalez: They found that most people didn't do very vigorous exercise, and instead, those who met the CDC's exercise guidelines of at least 150 minutes of moderate-intensity aerobic activity every week achieved this mainly through activities like walking or cycling, or even doing household chores or playing a sport.

    All the participants who were active enough to meet those guidelines still had a lower risk of all-cause mortality.  

    [00:14:40] Jonathan Wolf: And so that like lower risk of all-cause mortality in like, like normal speed basically means they were just less likely to die from anything. Is, is that right?

    Yes, exactly.

    And they were able to do that, you're saying even without the high-intensity exercise, so even just with, 'cause in fact, you're saying not many people in reality were doing this despite this. People who were just walking more, maybe doing a little bit of sport with their friends or cycling, were having this really big impact on just being alive.

    [00:15:11] Javier Gonzalez: That's right. So, the lower intensity activity was enough to have this beneficial effect on their risk of death. But what the researchers also found was that people who exercised more vigorously had an even lower risk than those who exercised more moderately.

    [00:15:30] Jonathan Wolf: Brilliant. So, Javier, you've taken us on this tour of the topic. What's your verdict on cardio exercise? How much and how often should we be doing it?  

    [00:15:38] Javier Gonzalez: So as I hinted at earlier on, something is better than nothing but more is better than less. So movement is key and doing it relatively frequently, trying to incorporate some into our daily routine can be helpful.

    And if we enjoy doing shorter amounts of exercise, then we should probably raise the intensity. If we are not so keen on the intensity, then that's fine. We can still get a load of health benefits from exercise, uh, but we probably need to do it either, either even more frequently or slightly longer in duration.

    So finding what works for you is probably key.

    [00:16:15] Jonathan Wolf: And I think life is also about compromises, right? I think about my own exercise regime, which is definitely driven by health benefits rather than the joy of like going to the gym. I get no joy going to the gym and a great deal of joy at the end of the session knowing that I've finished it Javier.

    Um, and so I end up going three times a week, which feels like an acceptable compromise because I just think I can't do more with Zoe and my family and all the rest of it. Is that a good trade-off? Am I losing out massively by not going, you know, five times a week?

    [00:16:49] Javier Gonzalez: No, that sounds great. We get most of the beneficial effects from going from very low or nothing to something, and then it's diminishing returns thereafter. 

    So the three days a week, you're getting a whole load of health benefits there. And I guess the other thing I'd be keen for listeners to think about is that. Physical activity is more than just those exercise sessions in the gym, and there are small things we can do in our daily life to increase our overall physical activity, things like taking the stairs or just increasing the number of steps we take throughout the day. 

    [00:17:20] Jonathan Wolf: And I was going to ask a bit about that because on the other hand, what's happened for me, you know, from the start of COVID and then continued is suddenly I do a lot more working from home than, um, than I did before. And, uh, I suspect there'll be quite a lot of people listening to this call who are also sort of at home more than before. 

    How worried should I be about the fact that actually I'm basically sitting in this chair and I'm not doing the, the commute that I, that I would have done before? I'm sure it's really early, so you're gonna tell me there's not all the papers, but what's your sense?  

    [00:17:55] Javier Gonzalez: Yeah, like you say, I haven't seen hard evidence, but I would agree with you, at least my own experience of working from home from the office is my step count is always lower on a day working from home than than working in the office without that commute. 

    Um, as a, as a practical message, I think we should probably be aware of that and try to incorporate, um, some kind of movement throughout the day, maybe build it into your schedule, um, in the time that you would be commuting if that's possible.  

    [00:18:21] Jonathan Wolf: I think it's really interesting. We should come back to specifically that topic because I think that, um, it is harder to be active. 

    I'm definitely less active, but I've been starting to try and add things into my day to sort of force me to do things because it's really tempting. The biggest plus for me is that my study, where I'm sitting right now, is at the very top of the house, and the kettle, uh, is at the very bottom of the house, and as anyone who knows me knows, I'm completely addicted to tea. 

    So half a dozen times a day, I have to go all the way down in order to make a cup of tea.  

    [00:18:55] Javier Gonzalez: Exactly, that sounds like a great tip with, um, kind of the habit of making a cup of tea, and you get a little goal at the end of it of a nice cuppa after you've walked down the stairs.   

    [00:19:05] Jonathan Wolf: Javier thank you so much. If you've enjoyed today's podcast and perhaps you'd like to learn a little bit more about how your exercise and your health works for you, you may be interested to try ZOE's Personalized Nutrition Program. You can learn more and you can get 10 percent off by going to joinzoe.com/podcast. I'm Jonathan Wolf.

    [00:19:22] Javier Gonzalez: And I'm Javier Gonzalez.  

    [00:19:25] Jonathan Wolf: Join us next week for another ZOE podcast.

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