Is Running Bad For Your Heart?

Now here’s a funny thing: I was about to write a few linked posts about the importance of exercise for health and the difficulties of changing habits and persuading  adults to make even a minimal effort, when I came across an article warning that exercise might have dangers. (Not that there's anything in it to change my plans as only good things can happen if someone moves from inert to 150 minutes a week). No the dangers are for those who are are worried about their health but for those who become intoxicated by the challenges, the idea of pushing back physical limits, and addicted to the feeling of being both physically empty and extremely satisfied.  Doing too much, or more specifically taking part in endurance events like marathons, triathlons, or ultramarathons might not actually be too healthy. There may be some unwanted adaptations to the heart and it is possible there is a dose effect so that just as too little exercise is bad for a body running too much might not be so good!

The origin of the concern was a paper has been published in Mayo Clinic Proceedings entitled ‘Potential adverse cardiovascular effects from excessive endurance exercise’ and many of you might not want to read any further than the title. Feel free to close your eyes, put your fingers in your ears, say “I am not listening!’ or ‘this cannot possibly be right because I don’t want to believe it’. If you write for a newspaper you can do this at slightly greater length. That’s OK as long as you are clear in your mind why you run and know that if you run for more than about 30 minutes a day you do so for reasons other than health.  However although we might want to continue doing what we do we should not treat unwelcome sounding research like and leave it unopened like an unwanted bank statement. We must face it dispassionately to see what the researchers actually say and be prepared to put aside our preconceptions. Before doing so though we can be strengthened by the thought that what is actually proved in any scientific papers is usually very specific within precisely defined limits which often do not bear the weight of the more generalised (and lurid) headlines.

So what to make of the Mayo paper?  Well from my lofty position of a non-expert it looks like a good survey of what is known about the effect of extreme exertion on the heart. It shows evidence that the hearts of highly trained athletes can enlarge and thicken in a way that would be seen as worrying for a normal person and there can also be scarring and other damage. However we don’t know enough about what that means for overall health and longevity, as the authors recognise in the abstract: 

However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity.

Nevertheless there is enough in this paper to get one thinking. But it must be emphasised that the authors are not warning about exercise of itself, instead they are raising the question as to whether there can be too much of a good thing. They explicitly offer no excuse for the couch potato to remain inert as their opening sentences make clear:

Regular exercise is one of the cornerstones of therapeutic lifestyle changes for producing optimal cardiovascular (CV) and overall health. Physical exercise, though not a drug, possesses many traits of a powerful pharmacological agent. A routine of daily physical activity (PA) stimulates a number of beneficial physiologic changes in the body and can be highly effective for prevention and treatment of many of our most prevalent and pernicious chronic diseases, including coronary heart disease (CHD), hypertension, heart failure, obesity, depression, and diabetes mellitus.¹ People who exercise regularly have markedly lower rates of disability and a mean life expectancy that is 7 years longer than that of their physically inactive contemporaries.

The point needs to be emphasised because there is no way you want a simplified message that running is bad for your health to seep into the public consciousness. It shouldn’t from this paper, which is a restrained academic review that does not editorialise. However that is done by the authors in the BMJ journal Heart, where they are clearer in describing the effect of exercise as a U curve where too much high intensity work loses some of the gains of a more moderate regime. (It can be found here but unless you have a subscription or access from a library it is not worth the £24 they want to charge. Instead watch the TED talk that covers the same ground). 

The article has caused more controversy because it inspired the article in the Wall Street Journal I previously mentioned. As is common for newspapers the headline and opening paragraphs were overly alarming, even if there was more balance further down the piece (as is also common in newspapers). This has been a push back with some people to contest the conclusions (e.g. here and here) and a little flurry of concern.

My take (for what it’s worth - and that is very little because it is just the intuitive response of someone who runs about a bit) is that I am very ready to believe that there is a sweet spot for exercise to offer maximum health benefits, which might not accord with the amount of work needed to fulfil other ambitions. It is very likely that more might not mean better especially for those of us over 50. But I am not sure if I have to worry too much. I may be old but the amount of running I do faster than 8 min miles is vanishingly small. I, like most people, am probably well within the boundaries of exercise being a good thing. However the problem is we cannot precisely define where those boundaries are. Take for example easy exercise: apparently we can walk as much as we like without hitting  a point of diminishing returns but does that also apply to slow, low intensity running?  If so the majority people who run marathons have no worries because, from the middle to the back of the pack, the long slow running dominates training (and the race). For most people the debate about a U shaped exercise curve is irrelevant because we don’t run hard or fast enough to reach the bottom of the U. The people at risk are the seriously competitive and they are the very people whose motivation has nothing to do with wellbeing or health. But the amount of that risk, if at all, is not yet known. 

It is all neatly summed up in an article in Outside about the original Mayo review: “high-intensity, high-volume exercise is really, at this point, a black box in terms it what it does for you over the long haul.”

Juneathon 2012 Day 23 - Clog Dancing

Juneathon 2012 Day 23 - Clog Dancing

Cycle - 17 miles, Time - 1hr 14min, Weather - Scudding grey clouds, blustery

As I was cycling into Harpenden I was startled to hear some yells, clatter, drumbeats, and a fiddle. Clog dancing was the last thing I expected - but there it was, happening in a tiny space outside Pizza Express. As is common with many such events in England, the shoppers passed by half turning, glancing out of the corner of their eye, not wanting to become drawn in. A handful of people stood and watched but mostly all the fun was had by the participants.

Seeing as clog dancing developed out of the cotton mills in the time of the industrial revolution, when workers would tap their feet to the rhythm of the machines and then later have competitions to see who could produce the best, most intricate rhythms, it is obvious there would be a team in Harpenden. The dark satanic mills of Hertfordshire are notorious. 

But no! I should not be sarky, it is unbecoming. Long ago I knew there was a team in Harpenden as a friend of mine who moved down from St Helens, joined it. Also the enjoyment the participants get cannot be gainsaid.

Fitness is a growing public health concern and the key thing in getting someone to do something regularly is enjoyment. For people (with more of a sense of rhythm than me) dancing is the answer. I want to see more of this - dancing in the streets.

Juneathon 2012 Day 8 - Exercise and depression

Juneathon 2012 Day 8 - Exercise and depression

Walk - 3.3 miles, Time - 1hr 5min, Weather - high winds with rain

The study in the BMJ on facilitated physical activity as a treatment for depressed adults has already been well discussed and just about every point I would want to make has already been made. But I can't let that stop me,   being late is one of my specialities and the subject of exercise and health is central to this blog.

First of all some background. There is a lot of anecdotal evidence that exercise can affect mood and help people cope with depression and a structured group physical activity programme is recommended by NICE as an intervention for those with subthreshold depressive symptoms. However the academic evidence is scant and the Cochrane Review of 2010 found that when data from  25 trials was combined,  exercise did seem to improve the symptoms of depression, but there was uncertain as to how effective it was, or what the most effective types of exercise were. So it is an area ripe for further study.  A heavyweight study from Bristol University would therefore seem to be just what was needed. 

It is a proper large scale study with 361 adults split into two randomised groups one of whom received normal treatment, the other normal treatment + support with an exercise programme. Their conclusion that the exercise support programme they used (3 face to face sessions and 10 telephone calls with a trainer over 8 months) had no noticeable extra benefit over normal treatment must therefore be taken seriously. But all that it really shows is that a particular type of intervention did not work. It did not show that exercise could not help people with depression and it had no information whether there were differing effects with different types of exercise. 

Unfortunately that was not how it was reported. The news bulletins all reported that exercise made no difference. This was not really the journalists fault because it is very much the line of the press release (upon which all stories were based). However there is a thin line between this and an interpretation that 'scientists prove exercise is no good at all for depression'. Some people who suffer with depression read it that way and reacted with outrage. It seemed as if someone was trying to invalidate their own experience.

Simon Hattenstone is a thoughtful and entertaining writer for the Guardian but his immediate response reads like a howl of pain. You cannot lightly separate a man from knowledge he has gained from his own experience. Unfortunately you also cannot generalise from that experience and think it is the same for everybody. His article was fisked by Pete Etchells, in a way that not only  showed what was wrong with his response but also pointed out some of the limitations of the study itself (it is well worth the read, including the comments). Other good summaries have also been written by Tom Chivers and Martin Robbins

I find this all rather heartening. There was a study the reporting of which made claims that could not fully be supported by the research, there was a kickback and then there was an attempt to make some sense of what was actually said in the initial report. This is good because too often the initial, simplified news headline is repeated and repeated until it becomes accepted as fact. This subject has caused more debate, perhaps because of the  number of people with personal experience who are in a position to write about it, and report itself has been looked at more closely.

This attention might also help some of those who initially reacted with hurt to the news items. Mark Rice-Oxley started his response by saying: "The problem with arguing with science is that it is often an uneven contest, a bit like hitting a steamroller with a stick of rhubarb." But it is not like that at all. He only needs to look at the Responses attached to the article in the BMJ to see how the subject can be engaged and the way the limitations of the study can be exposed. From that it is very clear there is still an awful lot more we need to know and huge scope for further research. The subject is far from settled.

P.S. Any time there is a claim about health in the papers the place to go for context and evaluation is the 'Behind the headlines' service from NHS Choices. Its reporting of this issue was, as ever, excellent.

P.P.S. I should also mention my blogging friend Travelling Hopefully who tackled this subject before me and covers much of the same ground,

P.P.P.S. Today's picture of blurry trees is my attempt at showing how windy it has been.

Janathon 2012 Day 20: Exercise and Health

Janathon 2012 Day 20:Run - 3.6 miles, Time - 44min, Weather - cloudy, windy, bleak

Another day, another slow run keeping the heart rate down. There were signs of progress as I managed to run quite long segments with a flat heart rate. Huzzah! Us runners are very simple folk - all we need is a little bit of encouragement and everything seems brighter, even if the weather is dreich. 

Over the past few days I have been superficially looking at the evidence for the benefits of exercise. i started with a video that suggested exercise was a magic treatment - the single most effect way of improving general health, followed it with a correction which said the evidence wasn't quite as dramatic as presented. This was followed with a couple of Cochrane Reviews that looked at the effects on specific complaints.

This is not good enough - there needs to be more of an overview. In 2004 the Department of Health published a report 'At least five a week: Evidence on the impact of exercise and its relationship to health', which can be downloaded.  Table ! summarises the level and strength of evidence for a relationship between physical activity and a number of chronic conditions

For me the most important thing is the distinction between the preventative properties of exercise as opposed to its use as a therapy because this makes it clear that there is much stronger evidence for the role of exercise in preventing illness rather than helping with a cure.

P.S. The photo is another one from Monday - some blossom to balance up the greyness of the day.

Janathon Day 18: Avoiding feeling bleak

Janathon Day 18: Run - 2.92 miles, Time - 32min 47sec, Weather misty moisty

Another picture from Monday as I took none today - it was too grey and oppressive. At the moment I am trying to avoid feeling bleak.

Today's run was a help, just because I did it. It would have been so easy to continue to mope about yesterday but I didn't. I adopted the shock tactics of rolling out of bed, into my running kit and out the door before my brain could start to argue. Still dazed I pushed the start button on my watch and was off. 

Just like yesterday my heart rate started to go a bit crazy but this time I decided to run 3 miles whatever and pay more attention to the heaviness of my breath. I stopped and started a few times but the heart rate eventually evened out and I ended feeling that I had achieved my goal, even if it was on average a few beats higher. Far more important than an arbitrary number was the feeling that I was doing something

The feeling you get from running links in with another Cochrane Review about the effect of exercise - this time on depression. The overall conclusion was that it has a positive effect but one that is difficult to quantify. It is hard even to say what exercise is the most effective. There is thus plenty of scope for more methodologically robust trials to discover dose and effect

It is interesting that Cochrane Reviews, which are the nearest thing we have to a summary of the current state of knowledge on health matters, seem to show that we know very little for certain. Yet people still have to make recommendations and the current one of 30 minutes a day of any type of exercise seems to be prevalent.

My next task is obviously to try and find out where it comes from

Janathon 212 Day 15: Some progress

Janathon 212 Day 15: Run 3.17 miles, Time - slowish, Weather - crisp and cold, bright and blue

A glimmer of hope today: I managed to run most of the way without walking to reduce my heart rate. It was not fast but at least it was a sign that the current discipline might become  becoming manageable; a sign that things are not hopelessly stuck. Huzzah!

Everything I have read about base training emphasises that it is a matter of patience - and so patient is what I will be. I am now looking forward to my next run to see if the progress will be maintained.

But enough of me. I need to return to the subject of exercise and health and the evidence of benefit

The obvious place to start is Cochrane Reviews, which are systematic reviews of the primary literature in health care and health policy. They have done a number of reviews about the effects of exercise. The first I looked at concerned its effect on type 2 diabetes.

The findings were:

Fourteen randomised controlled trials comparing exercise against no exercise in type 2 diabetes were identified involving 377 participants. Trials ranged from eight weeks to twelve months duration. Compared with the control, the exercise intervention significantly improved glycaemic control as indicated by a decrease in glycated haemoglobin levels of 0.6% (-0.6 % HbA1c, 95% confidence interval (CI) -0.9 to -0.3; P < 0.05). This result is both statistically and clinically significant. There was no significant difference between groups in whole body mass, probably due to an increase in fat free mass (muscle) with exercise, as reported in one trial (6.3 kg, 95% CI 0.0 to 12.6). There was a reduction in visceral adipose tissue with exercise (-45.5 cm2, 95% CI -63.8 to -27.3), and subcutaneous adipose tissue also decreased. No study reported adverse effects in the exercise group or diabetic complications. The exercise intervention significantly increased insulin response (131 AUC, 95% CI 20 to 242) (one trial), and decreased plasma triglycerides (-0.25 mmol/L, 95% CI -0.48 to -0.02). No significant difference was found between groups in quality of life (one trial), plasma cholesterol or blood pressure.


So it had a good effect but not as overwhelming as promised in the video especially as it did not seem to improve quality of life.

Janathon 2012 Day 11: Circumspection

Janathon 2012 Day 11: Walk - 3 miles, Time 55min, Weather - clear and mild for time of year

I must make some sort of correction, or rather a reservation, to something I posted a couple of days ago.

I saw an illustrated talk on the benefits of exercise, which had been going round the internet, thought “that’s neat’ and posted it up. OK, up to a point - it is neat - but it is not the full story. I should have thought about it a bit more. 

I posted it because I am a believer in the benefits of exercise and it is a good demonstration but it is not the whole story. The story line is too strong and it seems the evidence is more equivocal than is claimed. 

This posting on the BMJ site is very good about the way we should look at such claims and  treat them with circumspection even if they support our own side - no make that especially when they support our own side.

The thing is that having posted the video clip I feel a sense of responsibility to delve a little deeper and find out what evidence there is about the link between exercise and health.

Janathon 2012 Day 7: Half and hour a day

Janathon 2012 Day 7: Walk - 3.5 miles, Time - 1hr, Weather - blue skies before the grey swept back in

I ought to be feeling shamefaced about the low level of activity in this years Janathon. A three and a half miles walk is more of a holding activity than anything else but it might be doing more good than I think.

This video is a little illustrated talk which proposes that exercise might be the most efficacious public health intervention. The surprising thing to me is how little is needed to have dramatic benefits. Just half an hours walk a day will do the job.

Obviously this is rubbish if you want to train for a marathon but it shows I should not belittle these little outings too much