A week or two ago, Ewen’s comment about down-hill running led me to pose the question about the balance of risks and benefits of fast downhill running – and more generally, the risks of long term muscle damage from forms of training that focus on eccentric contraction. I am still looking into the scientific evidence on this question – but it is a tricky subject because the type of long term damage that I am concerned about might not emerge for years and it is virtually impossible to conduct rigorous comparative studies over that time scale. There is little doubt that at least some people who do a lot of very demanding training do eventually suffer long term damage (see Grobler et al, Br J Sports Med, 38,697-703). This seems to be a greater problem for runners than cyclists, but whether this is due to eccentric loads, is not easy to establish.
Even more important for the average runner, is whether a minor, but nonetheless appreciable degree of long-term damage occurs in the majority of runners, but this is even harder to establish. In a fairly recent review Brancaccio and colleagues point out that downhill running is associated with increased release of the muscle protein creatine kinase into the blood-stream and that this might be associated with significant damage of muscles. They conclude that in individuals with evidence of muscle damage, intense prolonged exercise may produce negative effects, as it does not induce the physiological muscle adaptations to physical training given the continuous loss of muscle proteins. (Br Med Bull. 2007;81-82:209-30). I am still working on assembling as good a collection of evidence as possible.
Meanwhile I have been grateful to receive interesting comments from several people based on their experiences. Thomas, who is preparing for Boston this year, commented on a friend who had injured himself with down hill running in preparation for Boston, with its notorious down-hills. Jason pointed out that he has experienced a gradual reduction in the DOMS produced by downhill running after a moderate amount of down hill running at speed incorporated within his overall training plan. I think that taken together, these comments confirm that downhill running at speed has some risk, but a period of moderate amounts of fast downhill training leads to adaptive changes so that it is no longer as damaging. This of course is the training effect that is the goal of most training programs, and makes sense. It suggests that someone preparing for Boston might benefit from a moderate amount of down hill running.
It still leaves open the question of very long term consequences – but even if very long term adverse consequences are possible, this is merely a specific example of the risk that we take with any demanding training – and it is probable that gradual adaptation is less damaging than a single major stressful event without adequate preparation. So on balance, if I were preparing for Boston, I think I would incorporate a moderate amount of downhill running at marathon pace or slightly faster, into my program. However, a least until I have a better understanding of the situation I am trying to minimize the amount of high demand eccentric work in my program, and in particular, I do only a very small amount of light plyometrics.
However, my experience last week when I went all-out to hold off a challenge in a 100 metres sprint late in the afternoon with inadequate warm-up despite rapidly dropping air temperature, an hour or so after a mile race, illustrated the fact that subjecting ones muscles to large eccentric loads without adequate preparation is almost certainly more damaging than a gradual build up of eccentric loading in a sensible training program. However, as I remarked last week, sometimes life is more fun when you throw caution to the winds and I do not regret the choice I made, despite the fact that my wings have been clipped for the time being.
In fact my injury is not too bad; my hamstring complains a bit if I inadvertently stretch it when bending down, but it feels OK when jogging a few metres. Tomorrow I will probably go for a short, slow paced run.