Friday, 24 April 2015

Virgin Money London Marathon 2015 - Pre-race thoughts

So, this year my race preparation has consisted of more miles than in previous years (Figure 1). In the 8 week run-up to the week before London I covered an average of 130.5 km per week at an average pace of 4:50.3 mins per km.

Figure 1. Strava plot of my weekly distance (km) with the peak week (181 km) marked as the darker column.
Most of the runs during that period consisted of commutes to and from work (12.5km each way) with a light rucksack and heavy trainers. At the start of the year I was wearing some Saucony Echelons which I later discovered were the source of heel pain (my heel spur was hitting the rather hard plastic support and bruising it). I threw them away about 4 weeks ago and the heel pain has subsided dramatically.

I think the distance training has had an effect. I accidentally put in a 5km PB last weekend after two years stuck around 18:40. It was a soft target since I don't think I have attempted a fast 5km for sometime. But, the PB may not reflect my full aerobic adaptations since I was not in race kit and rather fatigued. I suspect I may be able to go a little bit faster - we will see.

My weight is finally back down to 60 kg (7 am weight - neither glycogen depeleted nor loaded). I would have liked to be a bit lighter, but this year I have paid less attention to it. I have resumed an Alpen breakfast, no lunch and normal tea regime. Tea in the evening usually involves more calories than most would happily eat....The 'skipping' lunch remains a deliberate strategy to force my second run of the day to bias away from carbohydrate metabolism and to ensure that during my evening feed my muscles are 'eager' to clear the glucose from my blood stream. It also creates a bit more time in the day for work: running has been eating into my working day.

The heavy shoes and running with a rucksack were designed to promote a general 'overload' response and produce a bit more muscle. But, I was being - perhaps - a bit too conservative because I wanted to ensure hitting a reasonable distance each week - I will use a heavier load in my next training period. Equally, I wore a coat - and earlier in the year - my pink hat and gloves to provide a thermoregulatory stress. There are three reasons for this. First, the warmer arms ensure that my sweat glands remained trained. They are essential for losing heat during a race (when the heat load rises tremendously). Second, the additional blood flow to the skin during training (in an attempt to lose heat) produces an additional cardiovascular load that won't be present during the race. The effect is that the cardiovascular training component of the run increases without having to run faster. This is critical for the older runner where high running speeds cause significant damage and limit training. Third the effect of this additional cardiovascular load during training is to promote plasma volume expansion. This is what results in the 'blood doping'-like effect of prolonged endurance training together with remodelling the heart around a larger stroke volume.

During the training block I did have a rather steep increase in distance - which luckily didn't break me. It was an attempt to see what sort of training a 2:45 marathon runner might look like. I did two weeks of it and decided that it might be something I could attempt in the future. I then rapidly regained my senses and dived into the London taper.

My taper is, as a result of the high distance, rather short. Currently my thigh muscles are twitching away and I am wondering if I have got it right. But, as usual I need to decide what to do at London.

Since I am a scientist I need to weigh-up the evidence. The training-based marathon performance correlation equation (Tanda) - based solely on how far and how fast I have run in the 8 weeks before the race - predicts around a 2:54 marathon. But, I have pushed that correlative equation into 'full causation-mode' and well outside from the dataset that Tanda used to produce the coefficients. This form of extrapolation makes it unreasonable to expect the equation to be more than a general indication of my likely performance - although it has been rather good in the past. My training diet has been a monoculture of relatively slow short distances with little race-specific training. However, much of it was done with coat, heavy trainers and a rucksack. So there are reasons to believe that I might either be in worse or even better shape than the formula suggests. My heart beats per km (a measure based on heart rate at a given speed which I have used to predict previous marathon performance) agrees with Tanda at around 2:54 - but, I have optimized my training to bring my heart rate down. The result of biasing my training in that way is that I may have broken that predictive formula too by failing to attend to other training adaptations. Finally my age-graded 5 km performance projected to a marathon is also around 2:54 - but, such predictions require that you follow some average aerobically-limited declining function with distance. Such predictions have over-estimated performance for me in the past and I have not - on the whole - been able to produce the long distance performance that my 5 km suggests.

Now, whilst almost all objective measures say that around 2:54 should be possible, my brain does not. This is, of course, a problem, and one of my own making. My training has not been 'steady-state' but consisted of a fairly steep and consistent increase in load with a progressive improvement in fitness that I have not really been able to test by racing. I suspect that what makes my brain adapt to improvements, in the absence of racing, may well be a slower time course than the physical adaptations. It is perhaps the key value of races - they provide hard fast efforts that are powerful confidence builders (i.e. mental confirmation of physical attributes that can only be known through testing them).

So, the aim here is a longer term one. I think high mileages may well produce results - given the appropriate training duration. Clearly, my short exploration into that area is not yet long enough to expect the proportionate results. Once London is over the real training begins - a longer haul towards 2:45. Quite how far I get before I either break or fail is part of the fun - but, I remain convinced that for most normal healthy people the limit of performance remains the extent to which they are willing to force training adaptations and the strategy they use to do so.

For London I am starting in Green Pen 2 - which is where the 3:15 runners are. I will get a sensible slow start there and plan a first mile around 7 mins per mile. Then I plan to gradually ease to 145 beats per minute which I should hit at close to 6:45 mins per mile. Then it will be a matter of keeping heart rate below 154 to halfway - how close I get depends on the conditions. I hope by then to have an average pace of a second or so faster than 6:45 per mile. The trick will be to manage the heart rate rise smoothly to about 162 at the end. I will look and see if I can find 'The Wall' at 20-23 miles. If I can't find it I will try and approach my aerobic limit for the last 3 miles - thanks to the inhaler my breathing feels like it can be tested. Ideally I don't want to push the last 800 m - but, I guess that is racing. If my heart rate rises faster than I expect I will deliberately slow down.

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