Minimising the risks: chronic inflammation

In my recent post I summarised the evidence indicating that running, at least in amounts up to 50 minutes of vigorous activity per day, is likely to increase your life expectancy, but nonetheless some endurance runners suffer serious ill-health attributable at least in part to their running. There is unequivocal evidence indicating transient heart muscle damage after endurance event such as a marathon; and unequivocal evidence that endurance athletes are at increased long-term risk of heart rhythm disturbance, such as atrial fibrillation. There is quite strong evidence that many years of marathon training increases the risk of fibrosis of the heart muscle and calcification of the coronary arteries. While the beneficial effects appears to outweigh the adverse effects for the majority, at least some endurance athletes suffer serious adverse effects. On the other hand, the evidence that the benefits appear to outweigh the adverse effects in the majority suggests that is sensible to try to identify what causes the serious adverse effects and take steps to minimise them, thereby increasing the likelihood of being among those who derive more benefit than harm.

Although the mechanisms of cardiac damage are not well established, there is a great deal of evidence regarding plausible mechanisms. We are not detached observers who can afford the luxury of waiting until the mechanisms are established beyond doubt, like climate change deniers who prefer to wait until the outcome is certain before acting. Rather, we are each an experiment of one, and we must make our decision for action or inaction based on the current evidence.

Inflammation and myocardial fibrosis

Perhaps the most plausible mechanism for adverse cardiac effects is a mechanism based on inflammation. Prolonged mechanical stress on heart muscle produces damage, which in turn elicits an increase in cytokines, the chemical messengers that circulate in the blood and trigger the events of inflammation which lead to laying down of fibrous tissue. This is the body’s mechanism for repairing damage and increasing the strength of tissues. But the initial deposition of fibrous tissue is slap-dash and unless redundant fibres are removed, the future function of the relevant body tissue is likely to be impaired. In the long term calcium is deposited at the site of damage, making the tissues stiff and inflexible.

In the case of tissues such as the plantar fascia, the misaligned fibres cause the pain of plantar fasciitis and the deposited calcium gives rise to the heel spurs visible on x-ray. In the case of the heart muscle, misplaced fibrous tissue has the potential to interfere with the electrical conduction pathways producing disturbance of rhythm. In the case of the lining of blood vessels such as the coronary arteries, the process is a bit more complex. The accumulation of cholesterol at the sites of damage to the lining of the artery plays a key role in triggering the inflammatory response. The Wellcome Trust have produced an excellent video depicting the sequence of events.

Minimising the risks

From what we understand of the mechanism, there are three key things we can do to minimise the risk of damage:

1)      Allow adequate recovery after heavy training and racing. Studies in animals and humans demonstrate that much of the fibrosis, though perhaps not all, resolves during an adequate recovery period.

2)      Build up training gradually. The tissue trauma that initiates the inflammatory process is less if the tissues have been strengthened by gradual adaptation. This is illustrated by the fact that DOMS is more marked if you suddenly increase training volume.

3)      Consume a diet that minimises chronic inflammation. Current evidence indicates that a Mediterranean diet, in which the pro-inflammatory omega 6 fats prevalent in the Western diet are balanced by omega 3 fats from fish and/or nuts and green leafy vegetables, is a heart-healthy diet.


It is noteworthy that these three strategies not only have the potential to reduce the risk of serious long term adverse effects on the heart, but are also likely to maximises the long term improvement in running performance.

In future posts I will discuss the more complex issue of cortisol and also the exacerbation of rhythm disturbances by excess potassium that is released from damaged muscle cells

6 Responses to “Minimising the risks: chronic inflammation”

  1. Ewen Says:

    Thanks Canute – good post. I like the strategies for minimising the risk of damage. Makes sense, even to the layman.

  2. Oğuz Kesimli Says:

    Thanks Canute. About “Build up training gradually” ; what do you think of annual periodisation of senior runners ? In my younger days I would plan macro resting month anually, and then start building up again. As years passed, build up becomes more stressfull, I feel adaptation to training more difficult. I plan now micro resting weeks 4-6 times a year after races.
    To be more specific, my usual routine of 10+hrs a week, decreases to 50-60 % for about 7-10 days after a HM race, all very easy running. Build up to my usual routine after a week of little running is more easier. I run 4-5 HM races in a year, rest weeks add up to 1- 2 months.

    I hope I made myself clear; sorry for my English.


    • canute1 Says:

      Thanks for your comment. I agree, that with increasing age, fitness is lost more rapidly yet recovering that lost fitness requires a much greater effort. Therefore, it is tempting to minimise the duration of recovery after a challenging race. On the other hand, because of the diminished production of anabolic hormones, it is even more difficult to achieve a good recovery.

      I do not think there is any simple answer to this dilemma. However, as I describe in my next post on cortisol and the stress response, there several different strategies for promoting a healthy balance between the training and recovery. Therefore, I try to minimise the need to cut training volume dramatically for extended periods by employing other strategies. These include sleep and relaxation techniques such as mindfulness, and a healthy diet. I consider that the evidence favours a Mediterranean diet. Once my muscles have recovered (typically a few days after a hard race) I re-introduce resistance training. However, I despite these strategies, I am struggling to prevent deterioration of my fitness with age.

  3. Robert Osfield Says:

    Hi Canute,

    I share your concerns about possible consequences of lots of training and racing.

    In the last few months I have started focusing as much on recovery as training itself, with sleep being central to this. A particular problem that I suffer from is a tendency towards insomnia and I suspect this has been one of the reasons I’ve been prone to injury in the past.

    I have had modest success with trying to improve my nights sleep, I’ve increased the number of nights that I get 6 hours sleep, but still awake and struggle to get back to sleep a few times each week. Now the Scottish summer has arrived, by 5am one is awaking to near full daylight so this doesn’t help. Yesterday I put up a black out blind in our bedroom and result, slept through till 6:30am! Fingers crossed this will help.

    Over the last month I have also started reading up about the health benefits of napping during the day so I have started to take half an hour off from my usual daily route and have a quiet lie down. I have only actually fallen asleep a few times over the past weeks, mostly just relaxed and practise a little mediation. I feel different after this rest period, I’m sure my body has been able to dial down even without the sleep.

    I am also being more conscious about physical, emotional and mental stress. I am trying to avoid adding too many stresses at once, so if I have more work stress to deal with I’ll adjust my training to lower mileage and more recovery paced runs.

    So far this strategy seems to be working out well. I have put in 4 months in a row of 200+ mile months, with several weeks over 60 miles/week, some over 80. I have various minor injury niggles along the way but so far these have all healed up with a couple days off from running. This is really exceptional for me, normally I’d break down after just a month of two of this quantity of training.

    For me combining a good diet, with rest and training in a way that includes plenty of recovery days works well.

    • canute1 Says:

      Thanks for your comment. I agree that integrated adjustments of all of one’s activities in manner that minimises unnecessary stress while promoting repair and recovery is required if you want to push yourself to the limit.

      In my next post I advocate mindfulness as a strategy for improved relaxation at times of stress and also for constructive focus of attention while running. In addition, I find it very effective in helping get to sleep. I used to have great difficulty switching off my thoughts when trying to get to sleep. I find that mindfulness succeeds within minutes on at least 85% of occasions. At present I seem to be turning into an advocate for mindfulness as the cure for all ills. I anticipate that as more evidence accumulates the limitations of this technique will be more clearly defined, but the existing evidence indicates that it is worth exploring.

  4. The Longevity of the Long-distance Runner V : Whole Body Factors | Canute's Efficient Running Site Says:

    […] discussed in a more detail in a blog post in 2014, the three key things we can do to minimise the risk of damage […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: