About negative splits

I was not going to write anything about marathon pacing. In fact, since I don’t re-read my own posts on this blog it is very possible I have already shared some views on the matter. But then I’ve started reading articles online about it and friends, colleagues and relatives have started taking part in autumn marathons, plus we have already witnessed a couple of majors recently with some impressive results (WR by Kipchoge and ER by Mo Farah), so I thought I’d share my take on it.

I guess two questions come to mind immediately when it comes to best pacing strategy:

• Positive, negative or even splits?
• Is it the same for elite as it is for recreational runners?

When we look at the best marathon results for the elite field, for example in last Sunday’s Chicago marathon, we see that the European Record and the Japanese record were achieved by running a negative split. This, of course, means the second half of the race faster than the first half. Mo won Chicago with an impressive 02:05:11 (01:03:06 for the first half and 01:02:05 for the second). He ran the second half of the marathon almost a minute quicker than the first.

Same goes for Osako Suguru and his Japanese marathon record. Osako ran the first half with Mo in 01:03:04 and then he ran the second half in 01:02:46 for a 02:05:50.

Also, if we take a quick look at Kipchoge’s mind boggling new world record of 02:01:39 we see that hi second half (01:00:33!!!!!) was 33 seconds quicker than the first half.

Understanding why those runners achieved those impressive feats running faster the second half of the race is understanding marathon running.

Let me bring in a caveat at this point and mention that obviously those runners not only are the best at their craft in terms of athletic prowess but they have also trained adequately for the event they are competing in. This means they have trained for the distance, as one would expect. When talking about the best of the best it almost seems a joke that I bring this up but later I will refer back to this point as it is probably a key piece of information.

So we start taking a closer look at how it’s possible to achieve that level of performance and still run the second half of the race faster than the first half after 13 miles of running. Surely the longer we run, the more we fatigue and the worst we perform. But in marathon running, given you have adequately prepared for the distance, the name of the game is energy. Fuel management.

When I say adequately prepared I mean that the body is strong enough to be on the road for that amount of time and muscularly we can take it. If we’re strong enough, and these athletes are very strong, suddenly the marathon becomes about regulating the effort, about managing our fuel stores over the course of the distance.

The way I have always imagined it is by visualising a car with a fuel tank. The size of the tank will depend on your training. The higher aerobic capacity the bigger the tank. The fuel in the tank powers the car engine. When we run a short race we never have any problems with fuel, the issues are more with the speed of the car. We may not have a fast car but we can rev it to the limit and push it to its maximum as the amount of fuel available is always sufficient to finish the race.

Marathon running, however, throws in that energy variable to the mix. Suddenly the speed of the car becomes relative and dependant on more important variables such as the chassis of the car, the durability of the tyres and the amount of fuel available to us. Not much point being able to speed up to 140mph if that means we run out of fuel or the tyres disintegrate after 10 miles.

So marathon runners need to train to ensure the body has the right “durability” and that the size of the tank is big enough to store a large amount of fuel but, more importantly, that we are also efficient with the use of that fuel.

We’ve all experienced the motorway roadworks where we’re forced to do 50mph for a few miles and suddenly the car’s MPG reading starts telling us we can now travel farther on the same amount of fuel. That is the essence of what marathon running is about.

In this simile, training for a marathon when understanding the fuelling aspect is about increasing that efficiency so that we can still travel the entire distance, not at 50mph but, at the fastest possible speed without running out of gas.

If our engine is not primed for endurance the car will start consuming unsustainable amounts of fuel and sooner or later, usually around mile 20 we run out of gas. The wall.

As the tyres start to degrade or the suspension goes (or whatever car part that starts malfunctioning — I am not really a car person) the car will start requiring larger amounts of fuel to maintain its speed.

The reason a negative split or even split strategy works for the elite is because they already have the fast, reliable car and their main worry then is fuel.

So they start at a speed that allows them to use just about the right amounts of fuel for when the tyres start degrading a little bit, or for when the chassis starts feeling the bumps of the road. They need to constantly have enough fuel to keep the speed going.

What then happens is that, as they get near the finish, elite runners can start using up more and more fuel to speed up with the view to run out of gas just as they cross the finish line. Any fuel left in the tank after the finish would be considered as waste as it could have been used to power up the car to go a little bit faster even in the final mile or two.

When we decide to start banking time, because we know the car will start falling apart so we might as well make sure we’re ahead of where we should be, we are being short sighted.

We are not thinking about the entire distance. That banked time comes at a cost we cannot afford. Banking time uses up way too much fuel, and we may not realise it at the time, but when we do that the race is already over. We just don’t know it yet.

In fact, banking time feels great. We’re speeding through the early part of the race making the most of a primed machine. If the race was only 10–15 miles shorter we would power our way to the finish. We’d smash it right out of the park.

We think that, as the car starts becoming less efficient, we will be able to reduce speed and get us over the line but the more accurate physiological fact is that once the car is out of fuel it’s game over.

The amount of energy it takes to move the car even at slow speeds over the final 10 miles is way more than we realise. The car suddenly is the heaviest car ever and we can’t even push it to the finish.

Now, let’s separate concepts. Pace, intensity and effort. The name of the game in negative splitting is to slowly crank up the pace in the second half of the race. For well-trained athletes, even non-elite, that fine line can be as little as 4–5 seconds per mile (below in yellow).

It can go from about 99% of the target marathon pace early in the race to about 101%. A healthy negative split can be anything from 30 to about 90 seconds. Less than that it could be considered even splits and more than 90 seconds difference I would already consider a miscalculation in terms of time lost in the first half.

Intensity I link to heart rate. It’s a real value of beats per minute against your maximum heart rate. It helps understand how hard you are working at any given time. In theoretical terms, and based on experience, we may start the marathon at around 75%-77% of our heart rate max (Formula HR value = (HRmax-HRrest x HR%)+HRrest) to then stay at around 80% until the first hour. Then up to about 88%-90% until the final 20–25 minutes where we can crank it up to about 97%.

We don’t really get to 100% as our fatigued body will not be fresh enough to get to maximal intensity (one we would get to at the end of a 5k).

And then there is effort. Or think of it as perceived effort actually. That is the level of effort we are sustaining given intensity, pace, mental and physical pain, etc.

We may start the race at a very low percentage (no effort at all to maintain marathon pace for the first few miles) but soon get into the 30%-40%. Here you can apply the famous saying “the marathon starts at mile 20”. That means that at that specific point we may go rapidly from a manageable effort to pain levels and work rate reaching 90% and getting close to 100% for the final mile or so. When it really hurts.

To the second question then. Is it the same for elite as it is for recreational runners?

We know elite runners have the best cars. Efficient and durable. But we’re not elite, our car is an old banger and we need to fuel it several times when running for over 4 hours. Chances are it will start breaking down for non-fuelling reasons anyway. Anything can start malfunctioning. The longer you’re on the road racing, the more chances you have of breaking down. Suddenly the speed of the car and fuel efficiency are not really key variables to worry about as you will have to make several refuelling stops anyway. Finishing becomes the priority over finishing fast.

And that is where specific marathon training can help. I can’t really put my finger on where precisely the line is, but somewhere between 3 and 5 hours the principles of the pacing strategy change. It no longer becomes about fuel but it becomes about car integrity. Will the tyres last? That is more of a limiting factor than fuel when having to pound the roads for a long time. Joints, tendons, muscles cramping up… it’s a different ball game altogether.

Even the elite runners would have problems performing perfectly after 4–5 hours of running. In fact, the equivalent would be the elite ultra-marathon runners and, after doing some light reading on the subject, even they would tell you the body is not designed for that level of endurance. The vital organs start suffering under the stress of sustained running for those amounts of time.

But having experienced marathons between 2.35 and 3.30 I would definitely back negative or even splits running for up to that time (3.30) and possibly even up to 4 hours. The key becomes what kind of training have we done to:

A) make our car sustain the hours of racing — Long runs, strength work, minimum weekly volume, etc. and…

B) become more efficient at race pace — tempos, intervals, long runs finishing at marathon pace, etc.

And before I close this one up I will make one more point (which I have made in previous entries)… Just because the vast majority of people are not able to run a negative split it does not make it the wrong strategy. Pacing strategy is the icing on the training cake, it does not solve lack of specific training.

If you have not trained adequately for the distance and are not in shape to run the time you are aiming for there is no strategy that will help you. The marathon will find you out and ruin your day!