Monday, 6 January 2014

Introducing the concept of "Aerobic Resilience"

I'm now into my forth year of running Ultra-marathons and this year will take my biggest challenge so far - running the West Highland Way Race that covers 95 miles from Glasgow to Fort William. Preparing for this race is both a physical and mental challenge for me, and having a rather analytical streak I'm drawn to try to understand how best to prepare for the challenge.  I did start writing a long reply on a friends blog about my thoughts so far, but it really deserved a blog post of my own, so I've put together my thoughts, a little rough and ready, but should help understand where I'm going.

A mass of advice, but a vacuum of scientific evidence and models

There is huge amount of material in books and our on the web about how different people prepare for marathons and ultra-marathons, really too much material to digest especially as advice can conflicts, and in particular ulra-marathons have almost no scientific studies that might help us understand what might best.  I love an intellectual challenge as much as a physical one so I've been trying to distil things down to key factors that we should be training for when training for marathon or ultra marathon distances race.

Understanding Patterns that emerge from analysing Ultramarathon race results

From my analysis of ultra marathon results I've seen the trend for faster runners to slow less through races and for them to be able to  sustain a greater proportion of their shorter races paces (for instance looking at ultra vs 10k pace.)   I will need to write this analysis up, but as this is quick post I'll leave this for a later series of posts.

There is also a great deal of noise to the data, so while there are overall trends there is huge individual variations.  I'm hoping to come up with a simple but viable model to explain these variations, at least accurate enough to inform how one should train and paces races to get the best performances.

Introducing the concept of Aerobic Resilience

My current model is to view basic "Aerobic" fitness as equating to a runners 10k or half marathon distances where pace is near is tad faster or around the anaerobic threshold, but still the vast majority of energy production is aerobic.  One then introduces a "Resilience" factor that determines how well we can maintain pace as we run further.   A very simplistic mathematically model one could use might be:

  Speed(distance) = MaxAerobicSpeed *  (ResilienceFactor)^Distance

When ResilienceFactor is nearer to 1.0 for the best endurance runners and lower for those who struggle to achieve their potential at marathon or further distances.

The term Aerobic Resilience probably best sums up what I'm trying to encapsulate with this model.

With training for short distance races like 10k and half marathons it's all about maximizing our aerobic fitness, and topping this off with a small contribution from our anaerobic metabolism.

For longer distances like the marathon and beyond the contribution from anaerobic metabolism is less than 2% so it's it's almost entirely a case of maximizing our aerobic fitness.  However, it's not just about aerobic fitness, muscle damage, dehydration and glycogen exhaustion all play a part.  These other factors all combine to give our Resilience on race day.

When training for races of marathon and longer we have to train to maximize the combination of our Aerobic fitness and our Resilience.  Ignore either and you will not make the best of your potential.

For me the key factors in Resilience are Mental Resilience, Structural Resilience and Metabolic Resilience, The ReslienceFactor is the product of these individual factors.

Mental Resilience

Mental Resilience covers out ability to stay focused and positive through a race, to keep on top of discomfort, to monitor all our physical and mental systems and know what to do when areas need more support i..e take a gel, take a drink, take a walking break, get back running.  The mental side also includes the macro level planning over the whole race and management of pace.  For trail races one often has to keep an eye on the weather and navigation, so being able to have a fully functioning brain throughout the race can be crucial to not making costly mistakes.  You can also borrow a bit of Mental Resilience from any support you might have or from other runners, either competitively or collaboratively.  Things outside your own personal body can also impact on your Mental Resilience, for instance getting over taken or seeing what you feel is cheating might impair you mood or judgement on how to manage your own body and race.

Structural Resilience

Structural Resilience covers the ability of our bones, ligaments, muscles, fascias, cartilage, nervous system, digestion and cardiovascular systems to work continuously handling the physical demands placed upon without breaking down.  All these factors are multiplied together, if any one part starts failing then our overall Structural Resilience is compromised, our running economy will diminish as well as put a large strain on our Mental Resilience as the discomfort levels mount.

Metabolic Resilience

Metabolic Resilience covers the ability of our body to metabolise carbohydrates, fats and proteins efficiently.  Our ability to digest carbohydrates, fats and proteins efficiently also plays a part in longer races.  A runner who has poor ability to metabolize fats will almost certainly have a relatively poor Metabolic Resilience so will likely hit the wall, and will be very dependent on consuming carbs during the race.  Runners with ability to maintain a good pace whilst metabolising primarily fats will have good Metabolic Resilience and will require less fuelling during races.

Ingesting too much food when working too hard causes gastric stress, so a poor Metabolic Resilience puts strain on our Structural Resilience and our Mental Resilience.  A runner with good Mental Resilience would not give in, but slow down till the gastric stress passed then push on when the body settled.  This is just one example of how each of the element of Resilience are interconnected connected.

How to maximize Aerobic Resilience?

A simple model of long distance performance like Aerobic Resilience is only useful if it helps inform how we should train and prepare to maximize our performance come race day.  This is a big topic in itself so I'll leave putting down my thoughts for another post or two.  If you feel that this model is useful, or has elements that I should include just let me know, I'd like to refine it over the coming weeks, months and years to help myself and others enjoy training and racing as much as possible.


  1. Robert,
    I am not sure if my first attempt to respond got lost in cybsersapce, or is perhaps awaiting moderation. However, I will try again on the assumption it was lost.

    As you know from my blog, I have been exploring a similar issue, though my main focus has been the marathon rather than ultras. I have discussed the metabolic factors in some detail in my recent posts and in my most recent post, focussed on the mechanical factors, especially structural damage to muscle, as there is good evidence that muscle damage is associated with a drop off in pace after the halfway stage in a marathon.
    In my own recent discussion I have not dealt with the mental aspect of resilience, but agree that it is also important.

    As for the mathematical equation you present, I will be interested to see if the data does fit a power law with distance in the exponent. If this equation is to be dimensionally valid, the distance term should be specified relative to some standard distance. Do you envisage the standard distance would be 10K and the exponent would have the form (race distance-10K)/10K ?

    However, I don’t suppose the exact mathematical form matters all that much, unless you plan to use this equation to predict optimum pace in an ultra. Perhaps more important from the practical viewpoint is how you might train to increase your resilience. I look forward to your ideas on the implications of the concept of resilience for planning and monitoring training

  2. Sorry about the lost comment, I just wrote a comment with the Chrome browser and it got lost too, trying Firefox now.

  3. That's a very interesting concept, though I'm not convinced the 10k time has much influence on your ultra performance. I would assume your half or full marathon times are much more telling.

    The slowdown factor isn't quite so straightforward and can change dramatically with distance. My own marathon times are poor when compared to my 10 mile times (the MacMillan calculator always says I should run about 5 minutes faster for the marathon; this has been the case for almost 10 years now), yet my 100 mile/24 hours performances are significantly better. I think my main bonus in ultras is what you describe here as "mental resilience", though that is extremely hard to measure.

    I find the "structural resilience" is almost always due to muscle breakdown, especially in the quads. Sure, if you break a bone or rupture a ligament, your race will be drastically impacted, but that is a rare occurrence. Slowing down due to failing quads or calves, on the other hand, happens at virtually every ultra.

    No matter the details, the useful part comes in how to adapt your training in order to increase your race times, like you said. I'm very much looking forward to the next instalment.

  4. The MacMilliam calculator is something I've used in the past and have noticed in the last year that they have extended it to estimate ultra distances, but I haven't yet done any comparisons over a range of distances to see if it fits to the formula I've proposed in this post. It would be interesting to see how they compare, and also how well either map to performances like your own. Any chance you could email me a list of your recent times for different distances? robert.osfield at

    Real races have potential for lots of non-linear incidents, such as injury, getting pacing or fuelling wrong. One could average a set of races to derive ones average ResilienceFactor. This is an area where the Aerobic Resilience model should be able to improve upon estimates provided by the MacMillan calculator as you can personalize to fit better your own results and adapt them as your fitness goes up and down.

    I am also working on trying to estimate the ResilienceFactor from my training logs, this can't capture all aspects of Aerobic Resilience but should at least be able to give hints at the Metabolic Resilience with heart rate drift being the key indicator, i.e. if you have strong heart drift during long runs then it's likely that you have poor aerobic fitness and poor Metabolic Resilience.

    As you suggest Mental Resilience is hard to put a figure on. It is however, something you can probably work out as a general strength or weakness and train to improve it.

    Both of us have suffered with cramp in races so believe both us have a weakness here with our Structural Resilience that goes beyond just muscle damage and fatigue. Some runners never get bothered by cramp no matter how fatigued they are. It could be case of the weakest link is the one that breaks, so if you are stronger in Mental and Metabolic Resilience then it's likely that you'll be able to run faster longer and start putting more stress on Structural Resilience so eventually muscle damage and/or cramp starts slowing you down.

    1. Thomas, I have just started a bit of analysis of data provided by the MacMillian calculator comparing it to published data for records at different distances, and my own Aerobic Reslience formula and to me it looks like the MacMillian calculator is overly optimistic about marathon times - a clear discontinuity in pace change is noticeable. I will need to write this up in a follow up post, but it looks to me that this discrepancy might go some way to explain your apparent 5 minute marathon short fall.