Wisdom Wednesdays: Why your heart is the ultimate 'use it or lose it' organ - and what you need to do about it.

I was actually born with. So we're going to talk

about today through the lens of one of the most groundbreaking studies ever in exercise science, and it's called the Dallas bed Rest Study. And then there's been a series of studies after that about the Dallas bed Rest and Retraining Study and it's kind of got a fifty year legacy and this researchs really changed medicine. And after my own experience with heart surgery, I can tell you that this isn't just theory, it's actually life saving knowledge. And

it starts. The story starts in nineteen sixty six, five healthy young men in their early twenties, fit and no health issues, volunteered for a radical experiment what they had to do was lie flat on their backs for three weeks. No walking, no standing, no sleeky lapse to the fridge, just bed rest and probably a student's dream get paid to lie in bed for three weeks, But what happened

was a bit of a wake up call. In just twenty one days of complete inactivity, there are cardiovascular systems aged by what would normally take thirty years of living.

Their VO two max, which is they measure the gold standard measure of your cardio respiratory fitness or horsepower if you like it, actually dropped by twenty seven percent in three weeks, and their cardiac output, which is how much your blood how much blood sorry, your heart pumps per minute plummeted by twenty six percent, and the stroke volume, the amount of blood that's pushed out per heartbeat, dropped a whopping thirty one percent, and its submaxim sub maximal effort.

Just like light cycling or light jogging, Their heart rate and blood pressure skyrocketed. Their hearts were working harder, just doing less, And this was the original use it or Lose it research study, But then came a bit of a twist. These men spent the next eight weeks in a structured endurance training program. And this wasn't a walk through the park. It was rigorous aerobic and anaerobic training and it was five to six hours per week and

the results were pretty bloody stunning. Their VO two macs increased by forty five percent, so went way above what they were before they came in. Their stroke volume jumped forty eight percent, and their cardiac output and returned to it and actually even surpassed their baseline levels. And the cardiovascular damage from complete rest was not just reversible, it was reversible and actually went higher through targeted, consistent effort.

And remember this wasn't just a theoretical benefit. This is actually a seismic shift in how heart attacks were treated from their on no more prolonged bed rest after heart attacks. This was the genesis of cardiac rehabilitation. And if we

fast forward thirty years, the researchers tracked down the same thive men, now all still in their fifties, and they tested them again. This time there was no bad rest. They just wanted to examine how three decades of normal aging had impacted their hearts, and to the researcher surprise, their VO two max had only declined by twelve percent in thirty years, and compare that to the twenty seven percent crash after three weeks of bad rest. Now, what

probably happened was that training study that they did. That they went through. The bed rest and training study probably locked in for these guys the importance of fitness, and so they probably had lifelong exercise and that's why their hearts when they were in their fifties actually seemed a lot better than what was the original thirty years of aging. Right, But this time they actually trained these guys again, but this was a bit of a gentler program, and it

was long. It was two hundred and fifty minutes a week, and it was progressive overload. Right. They didn't start them as hard as they did when they were younger. They built it up over time. But again they got significant gains their VEO two max roles fourteen percent, right, not quite as much as in their youth, but that's that's massive. Like, if you're in your fifties and you can increase your VO two max by fourteen percent, that has a really

profound effect on your risk of all cause mortality. Now,

let's bring this study forward now into the future. Twenty eighteen, the same research team and this was at Dallas. They asked a big question, can you reverse cardiac aging in the middle age, not with a late level training, but with a doable, realistic, although reasonably vigorous exercise plan. So what they did is they recruited sixty one healthy but sedentary middle aged adult typical population and their average age

was fifty three. Half of them and were assigned a low intensity stretching and yoga control right, So these were the control group. They didn't do nothing, they were doing low intensity exercise and the other half got a smart structured training program. And this was two years and the

key ingredients of this program and I will send a link to this if you want to really get in and geek out, but essentially it was four to five days of training per week and it started off with moderate intensity aerobic work what we call zone two. Now you may have heard of zone two. That's in terms of heart rate training zones, and it's sixty to seventy percent of your maximum heart rate. This is the bread

and butter of endurance training. And if you don't have a heart rate monitor, you don't know your maximum heartbrate. The easiest explanation of zone too is you can talk, but you can't sing, right, So you should be able to hold a conversation, but somebody should know if they're talking to you on the phone that you're actually exercising. If you can sing, you're in zone one. If you

can't talk in full sentences, you're in zone three or higher. Now, this modern intensity aerobic work is really important because it is very very beneficial for our mitochondria and gives us what we call an aerobic base. And then they added in high intensity intervals and specifically they used my favorite protocol and the one that I'm actually using for my cardiac rehab, and it's their Norwegian style four x four protocol.

So what you do is you go four minutes hard and at the end of those four minutes you should be at ninety to ninety five percent of your max heart rate or a perceived exertion of nine out of ten. Right, So you do that for four minutes. Then you have three minutes of active recovery down to about zone two just to count, so you're keeping moving but at low intensity that three minute recovery, and you do four intervals, right, So it's four intervals with three recovery it's twenty five

minutes in total. And then they added into this one long weekly session of endurance training and importantly as well, they did twice weekly all body strength training. Right, so this wasn't brutal, but it was a pretty reasonable, vigorous exercise program, and it was calculated and it paid off. After two years of this training, their VO two max increased by eighteen percent. Now, this is a massive improvement

in middle age. And like I said earlier on this, if you're in your fifties and you can increase your VO two max by eighteen percent, there's not much else out there that you could do that would juice your risk of all cause mortality as much as increasing your view two march by eighteen percent. But there was a deeper win here. Their hearts actually got younger. So when they really dug into looking at how their heart was performing,

their left ventricular stiffness. So you're left ventrical, that's that you think about that the rooms of your heart, if you like you're left ventricle, is this important room? This is this is where the heart, the heart or the chamber that fills up with blood and then it squeezes and that's when your heart beats and actually pumps the blood throughout your body. So your left fend. The stiffness of your left ventricle, essentially how rigid or elastic it is,

is really important. And in these guys, their left ventricular stiffness drops significantly. That meant that the heart could relax better, it could fill more efficiently, and it could pump more blood per beat. Now this is really important. So with me, when I had that dodgy aortic valve, a bicuspit valve, what that meant was every time that blood pumped out of the left ventricle, and because my valve didn't shut correctly, over time, some of the blood came back in and

that stretched the left ventricle. Now I was lucky that I caught it relatively early. If I'd have waited another year eighteen months, my left ventricle would have got much stiffer and also would have stretched to the point of no return. And that's what we call heart failure. When you hear of heart failure, that's what it is. You're left ventricle is actually stretching to the part of no return, and it gets really stiff and it just does not work well. Now, what also happened in these people is

their stroke volume also went up. The amount of blood that they could pump out with every heartbeat, right, which is really important. The heart size actually increase, So this is a physiological adaptation. And a result of all of that is that the resting heart rate went down because the heart, because it was more efficient, didn't have to beat as often. In real terms, this meant that they were fitter, they have more efficient and more youthful hearts.

And in the control group, they didn't have any change, any positive change. In fact, their heart function decline because remember this is a two year study and they were two years older and they had that two years of decline. So let's break this down really simply in Layman's terms. So, when your heart becomes stiff, that left ventricular stiffness, it loses its ability to relax and fill with blood efficiently. That is a direct pathway to heart failure with preserved

dejection fraction. That's what we talk about, and that's an increasingly common and stubborn form of heart failure, especially and older adults. And here's the kicker that twenty eighteen studies showed that this trajectory is not inevitable. If you intervene in middle age, you can stop this stiffness from setting in the heart remains plastic or changeable into your fifties

and beyond. Now, the same research group did another study where they took people in their sixties and they trained them, and they didn't see the same results, right, So part of that conclusion was you got to get on this when you're in their fifties. But actually, when you look into the detail, they did admit that the training intervention that they did in the sixties wasn't as comprehensive as the training intervention in the fifties. So there's still a

little bit of a question. But what we do though is as your heart ages, it like all tissues in the body, they lose their elasticity, right, So what does this mean. It means that a couple of things. Number One,

your heart remembers. It remembers that three weeks of doing nothing can wreck you more than three decades of aging. So we have to be moving if we want to have a healthy heart. But it also means that consistent smart exercise, especially when it includes a mix of baseline aerobic zone two and high intensity interval training that doesn't

just increase your fitness. This is about cardiac uth. It's about making your heart younger, and if your heart gives up, it's all over, right, And we're not talking about marathons here, right. That twenty eighteen study met the public health guidelines right, one hundred and fifty to three hundred minutes a week, with some of it high intensity interval trainings and strength training.

I think that's also important in this study. It is achievable, it is sustainable, but you've got to do the work. That's the key thing. So the big take home here is if you're in your forties and your fifties, or you're guiding or know somebody is, this is the moment to get on top of this because the longer you wait, the harder it actually becomes. And if you're younger, don't be complacent because your heart can age really really quickly with lack of movement. In the end, your heart actually

wants and needs to be challenged. It was built to respond and it responds to your environment. If you do very little, your heart age is super super quick. But if you actually do do the training, your heart will respond and it will get and can get younger, and you just have to give it the right kind of push. And I'll leave you with probably my favorite quote of any research journal I've ever read, from the Journal of Applied Physiology in twenty twelve by Professor Frank Booth, legendary

exercise physiologist. He said, the human genome has not changed in over forty five thousand years. Their current human genome requires and expects us to be highly physically active for normal functioning, and that is certainly the case for the heart. Catch you next time.