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Why is it so difficult for older, particularly endurance, athletes to know how hard to train? That's a really key question, and one we will answer in this video. Whether you're cycling, running, rowing, or doing gym work, how hard should an older athlete train so as not to damage their heart? It also applies to climbers like Dr Peter Clarkson. He's an NHS cardiologist in the Scottish Highlands, and he sees folk like us when things go wrong. He'll also explain who's at greatest risk of sudden serious cardiac events. You do not want to meet him professionally, so you'd better watch this.
Let's be clear: fitness for health is not just cardiovascular. It's functional strength, mobility, balance, and body morphology, not just how much fat you're carrying but what your bone density is. Are you doing weight-bearing exercise? That is important. I love cycling, and I've done lots of cycling. If that's your favoured form of exercise, you're going to find it difficult to move through a wide range of motion, and it doesn't protect your bone density to the same extent because you're probably not weight-bearing. That's why this is part of a comprehensive, ongoing series looking at different aspects of health for older athletes. As individuals we have unique issues, so please check with your doctor before exercise. This is not medical advice for you, and Dr Clarkson cannot answer individual, specific follow-up questions. That's the disclaimer, done.
But there's always the question: what is too much? Is there something that's going to cause problems downstream by doing too much exercise? Can we as older athletes do too much? On the cardiac side, there are two things we are concerned about: coronary artery calcification and atrial fibrillation. We'll talk a little about both.
In 2023, a study of about 300 athletes aged 50 to 60 took part in the MARK-2 study, which is measuring athletes' risk of cardiac events, and more research will take place over the next decade. Endurance athletes are more prone to getting coronary artery calcification, which means hardening of your arteries, and this can potentially cause further cardiac trouble downstream. What the data is telling us so far is that it's particularly common in men, but it is more prevalent in people who spend a high percentage of their time doing very vigorous exercise. By very vigorous exercise we mean things greater than nine metabolic equivalents, which is generally heavy rowing, running, or pushing yourself very hard in cycling events. It doesn't seem that the overall duration of exercise makes any difference. If you exercise for longer, it doesn't seem to make any difference to coronary artery calcification.
So what are the current take-home messages? What I would probably take from that is that you need to spend a significant proportion of your time doing lower-intensity exercise as well. We definitely know that doing some high-intensity exercise is good for you. It's good for your VO2 max, it's good for your body in lots of ways, and I don't want people to stop doing high-intensity exercise on the basis of this small risk of coronary artery calcification. But as I said, it's the high percentage that seems to be the trouble. So I think sticking to the more 80/20 type of exercise that we're told to do, rather than pushing yourself towards a more 50/50 split, is likely to be more protective to your coronary arteries. We'll find out more as the decades progress and we get more information on this matter.
80/20 training is explored in this video, number seven in the series. It means that 80% of your training should be done at an intensity where you could hold a conversation but may struggle to get out the last few words. Limit high intensity to around 20%. This might impact your turbo training, especially in winter. Hard intervals on Zwift or another platform are more interesting than long steady rides and feel like proper training, but they are harder to recover from, and if such intensity is more than 20% of your training, you could be storing up a problem. There's no easy way to check. Unfortunately, the studies on this are all based on CT scans of the heart, and I wouldn't recommend people get CT scans of the heart to determine this, because you need to irradiate your chest to do so. The data is coming from looking at serial CT scans. We don't have a biomarker, and there's nothing physically evident by looking at someone from the outside. As a cardiologist, I can't tell who has coronary artery calcification without recourse to X-ray.
That fixation has continued pretty much for 40 years, and Peter's love of climbing is equally complex. I think it's a combination of multiple things. It is actually quite a complex sport, one that involves not just the physicality of things. I like the puzzling out of things. I like playing chess, so I like that sort of how do I join these dots together to actually move on a piece of rock and get myself up these things. He's a regular at the Ledge climbing gym in Inverness. His chosen sport trains his strength, balance, mobility, and more, as well as his cardiovascular system.
For all athletes, regardless of sport, there is one big red flag to look out for: central chest pain on exercise. If you're getting discomfort in your chest that is not easily localised, most cardiac chest pains we see involve people putting a hand on their chest and saying it's somewhere in here. If you're getting a deep pain that's hard to localise, particularly on exercise, you should definitely be concerned that there's coronary artery disease. Moderate exercise does seem to protect against the worst type of coronary artery disease, and there's no clear link to it from vigorous exercise either. The worst parts of coronary artery disease for us are the fattier plaques in your arteries, less like rocks and more like cheese deposits, which are more prone to rupturing. They are the ones more commonly associated with heart attacks later on. What we don't know is the downstream effects of coronary artery calcification. Are you more prone to heart attacks? We think you're probably more prone to angina and limitation from the hardening of your arteries, but it may be that you don't get many more heart attacks or sudden deaths as a result of coronary artery calcification. We just don't know, because the data is not there in abundance, due to the difficulties of population screening when it relies on CT scans.
If I was given the choice of completely normal arteries versus coronary artery calcification, of course you'd choose the normal ones. But if you were given a choice of hard calcified arteries versus ones filled with fatty plaque, I would definitely choose the calcified arteries. You don't really get a choice like that in life, though, but you have to understand how things are up here. After hearing that, I wondered what the implications are for HIT exercise, short high-intensity intervals. Again, the evidence is not yet clear, but it suggests they should be balanced by more moderate exercise. HIT should not be the only thing you do. You have to understand how things are.
In part three, we'll discover who is at most risk of a sudden cardiac event. First, atrial fibrillation and atrial flutter, for which I recently underwent tests. Previously I'd done a VO2 max test, and the ECG trace showed an unusual heart rate spike. It might have been an early warning of a common problem for older endurance athletes. Our heart works like this: you've got the atria on top, which is where the rhythm starts from. That's like a booster pump. It pushes a bit of extra blood into the ventricles, which are the main chambers that push blood into your lungs and around the body. We know that people who do a lot of endurance activity are more prone to getting atrial fibrillation than atrial flutter. Atrial fibrillation is a very chaotic rhythm of the atria, basically wobbling a bit like jelly. Atrial flutter is an electrical circuit caught up in a rhythm going around about five times a second around the right atrium, which then propagates into the atria. That means it's still inefficient. Your heart is running at a faster speed, and it doesn't have that contraction booster-pump effect before the ventricles contract and push blood into the lungs or around the systemic circulation.
Your left atrium has a blind-ending sac on the side of it called the left atrial appendage. In a normal heart, in normal sinus rhythm, the appendage contracts and pushes blood out of it. If you develop atrial fibrillation or atrial flutter, it no longer pushes blood out, and blood can form slow eddies and start to coagulate inside the left atrial appendage. The concern is that there is a small risk that this coagulated blood can dislodge, travel around the circulation, and if it lodges in one of the arteries deep in the brain, you will have a stroke as a result. The risks aren't huge, but we do know there is a risk in people with atrial fibrillation. Those at greatest risk of AF are those who do very little and those who do a lot of exercise, and on average it gets worse with time. Every 10 years of heavy exercise, your risk of atrial fibrillation increases by 16%, and your risk of atrial flutter increases by 40%, according to some studies.
I see people in my work who are athletic and develop atrial fibrillation, and many of them struggle with it, because it does cap the amount of exercise you can do. You lose that booster-pump effect of the atria, and your heart rate is often not as well controlled as it was before. Many of the drugs we're used to putting people on for control of atrial fibrillation, like beta blockers, are generally not suitable for the very athletic population. They cap the amount of exercise you can do, lower your maximum heart rate, and often give people a degree of fatigue on exercise as well.
At the time of making this, I am still undergoing investigations. It doesn't feel like AF, but I know it can come without symptoms and might only be detected by a family doctor or other health professional checking something else entirely. Usually, though, there are symptoms. Many endurance athletes are fairly well tuned to what their pulse feels like, and many check their pulse anyway. AF will give you an erratic pulse, and you cannot predict exactly when the next heartbeat will come, so you can feel that. Some people don't feel palpitations or don't wear wearables. You may feel capped on exercise, feel more breathless, or simply not feel the same as you did before. When people first start getting it, they get little bursts, which we call paroxysms. You get a trigger, it lasts for a few minutes, then reverts to normal. Those paroxysms get longer and more frequent over time until it drifts into what we call persistent or permanent atrial fibrillation.
So who is most at risk of a sudden, serious problem? It's those of us in mass participation events, sponsored to raise money for charity, or who otherwise feel compelled to take part. What is thought is that these people have a different threshold for saying, actually, I need to do this on this day, even though I don't feel very well. I'm going to turn up and do it anyway. The advice we now give people is that even if you're sponsored, if you're feeling ill on the day you're going to do a long endurance event, please don't do it. It's much better to look after your body than to think, I'll get through it, I'll wing it, I'll be fine, because you are probably pushing yourself into a higher risk by continuing to perform endurance events when you are ill.
Yes, the big scary stuff has never really been my bag, and I think it's very easy to get sucked into the cardiologist way of thinking, which is that physical fitness equals cardiovascular fitness. There are actually a lot of other facets to physical fitness as well as cardiovascular fitness. Muscle strength: are your muscles strong? What's your mobility like? Mobility is coordination. Is your balance okay? Are you able to move properly and put your muscles through a full range of exercise? For me, rock climbing covers both of those. You're working your muscles hard, and you're putting them through a full range of movement, expecting your muscles to contract and provide power throughout a wide spectrum of motion.
Huge thanks to Dr Peter Clarkson for his time and expertise. I'll release the full interview as a podcast soon. Subscribe, turn on notifications, and you won't miss it. In the next videos: the VO2 max you should be aiming for if you want to live an independent life at much older age, how to test your VO2 max more accurately than your smartwatch or app, and what to do to raise it. If you have enjoyed this, please share the video and the series with your friends and folks you know online. I am trying to encourage older athletes, and I think this takes a step towards keeping us that bit safer. Hopefully I've got more expertise to come, and I spend a lot of time trying to find it. In the meantime, you'll find the rest of the older athlete series here and some adventure cycling videos here. I'll see you again next time. Bye.