This article is the second of a two-part series exploring new research into marathon pacing.
Click to revisit Part 1: New Research Investigates the Challenges of Good Pacing
PART 2: A Look at the Physiology of Pacing
Having a basic grasp of what’s happening in your body while you’re running a marathon, and how and why that affects your pacing, can be extremely helpful for improving your own pacing and performance.
There are plenty of existing theories about pacing for endurance sports. Dr Dan Gordon is leading the research team looking at the data discussed in Part 1. He explains:
“There are six well-established pacing models:
• Going “all out”
• Positive split (running the first half faster than the second)
• Negative split (running the second half faster than the first)
• Even splits, with even pace (running at a steady pace throughout)
• U-shape: starting faster, decreasing pace in the middle, and increasing again at the end.
• Inverted U-shape: starting slower, increasing pace in the middle, and decreasing at the end.”
But what’s the most efficient pacing model? The prevalent thinking among club runners tends to be to aim to run an even pace (and also perhaps that the ultimate objective is a negative split, given that recent world records were set with negative splits).
Are the best pacers running an even pace? Part 1 of this article included a chart showing how the fastest 5% and 25% of runners are running at a much more even pace than the slowest 5% and 25%, and the scattergraphs showed how these faster groups were also much more accurate at predicting their performance.
So I asked Dan – is an even pace the way to do it? Or perhaps aiming for a negative split?
“Well, logically an even pace should mean that you will be able to run and not be exhausted at the end. But in practice, pacing is always variable – it oscillates constantly and is never really ‘even’. Within a mile, there’s all sorts going on – you’re speeding up and slowing down irregularly.
“The main point isn’t really whether you are running evenly, or running a negative split, but about how you’re managing your energy. The key idea in pacing theory lies with something called Critical Power (CP). CP is the highest sustainable exercise intensity your body can work at without getting too close to VO2 max.”
How does Critical Power work?
Dan puts it this way:
“Think about ability to exercise being based on two forms of energy: aerobic and anaerobic. The aerobic (using energy from oxygen) is technically unlimited. Anaerobic (using energy stored in the muscles), on the other hand, is very limited. Once you’ve used up the anaerobic, you’re going to struggle to get it back. And as you use anaerobic energy up, fatigue sets in.
“If you are working above Critical Power, you’ll drain the anaerobic energy store very quickly. Whereas if you’re working too far below CP, you’re probably not working optimally. But if you work just below CP, then you are using both sources while minimising depletion of anaerobic.”
What happens if we get that wrong, and go out too hard or not hard enough?
“There is already well-established evidence that if you start out too slowly, you’ll never make up for lost time. You only have to be out by around thirty seconds over a kilometre before you’ll miss the boat altogether and not be able to make that time back up.
“But the more damaging approach is to start too fast – as many of the poorest predicting groups in our data seem to be doing. If you start out above CP and drain the anaerobic resource, you will not be able to sustain that pace for long, and you will not get that energy back. Even if you then slow right down to an easy pace, you may remove some of the by-products associated with anaerobic effort (e.g. lactate), but you’ll not recover the energy expended enough to catch up with the time you lose in the process.”
So the best pacers (i.e. those running closest to their predicted times) are avoiding setting out too fast or too slowly?
“Yes, it would seem that the best pacers are able to judge their pacing to run just below CP, at the fastest pace they can tolerate before draining anaerobic energy.
“So, for a marathon runner, the key is actually to consider CP as the upper threshold for sustained work, while the lower threshold is the Lactate Threshold (LT-1)*.
“Therefore when we consider marathon pacing, we have to ensure that we never go above CP as this means we just deplete the anaerobic energy at a very fast rate and increase fatigue.”
*See our previous interview with Dan for an explanation of Lactate Thresholds for endurance running.
The research from Dan’s team at Anglia Ruskin University in Cambridge is valuable to understanding marathon pacing because of the sizeable pool of almost 800 runners. Many previous pacing studies have relied on tiny sample groups, and have looked at other sports, or shorter distances. So I asked Dan what the pacing physiology looks like in practice, based on the new data:
“In pacing studies based on other sports or shorter distances, there is often a ‘U’-shape curve: for example in Olympic rowing, successful teams typically go out hard, cruise in the middle, then pick up at the end. It also happens in shorter running distances such as the 800m: athletes start fast, then go steady, then sprint.
“Our new large marathon data set confirms a different picture for endurance running. What we are seeing is that ALL groups are conforming to a pattern of slowing down throughout the race. Even the groups of best predictors are slowing.
“There is less of a decrease of pace, on average, among the best predictors, particularly among the faster runners. The poorest predictors, on average, are starting too fast and slowing down significantly towards the end of the marathon.”
The mind and the body
It seems there’s a fine judgement involved here? How do I know where my Critical Power is? What pace should I be running at, and how do I know if I’m going too fast?
“It’s a big challenge. But this is where experience becomes vitally important. We know that more experienced runners tend to be much better at understanding an appropriate pace. The data we’ve got shows the more marathons you’ve done, the better a pacer and predictor you’re likely to be.
“Pacing is a combination of two constructs: biological and emotional. The biological construct involves systems physiology: critical power, training status, VO2 max, economy… all those types of variables.
“The emotional construct is your ability to cope with sensations such as pain and fatigue, and thrown in there are factors like arousal and adrenaline.”
So how does experience help with this?
“The key thing is perceived exertion, which is a function of both biological and emotional factors.
“If you’ve never run a marathon before, the ability to pace is on very thin ice because there is no frame of reference for interpreting the information. If you’ve only run one 20-mile run in training, you’ve got no means of working out required exertion and using the information available to you.
“But if you have lots of experience of how you’re likely to feel during a marathon, you become a much better judge of the effort needed. Experience helps with everything, such as:
• understanding the tendency to go off too fast, and how to control it;
• intuitively understanding the role of adrenaline at the beginning of the race; and
• expecting and dealing with the feelings of pain and fatigue.
“So there’s a big gap between people who have never done a marathon before, and people who have run several.”
How can I monitor my pacing?
Runners are different. Some like to check their watch on a very regular basis, others prefer not to look at all. Some have a strict pacing strategy that they intend to stick to, others try to run on feel. Some are obsessing over their finish time, others just want to complete the distance.
However you choose to run, we hope that learning more about pacing is useful. There are a few trends that seem to be coming across clearly from the research, such as the tendency of many of the poorest pacers and predictors to go off far too fast (this isn’t news of course, but it’s interesting to see it in practice). And experience seems to be a good indicator of better pacing.
Many runners find wearing a pacing band a helpful way to stay focused, avoid going off too fast, and manage the mental aspects of their race.
So The Flying Runner has created a new marathon pacing calculator which enables you to build your own pacing profile in a more user-friendly way than many of the existing tools on the internet, and you can output your own pacing band from your personalised pacing.
Your pacing band:
- Most standard pacing bands simply chop up your target time into equal mile divisions. We’ve developed something more flexible for you.
- You can create a pacing band based on a completely personalised pacing strategy.
- The calculator enables you to input a target time and you can choose to look at how you might pace your race with even splits, a positive split, negative split, and make adjustments to any particular mile splits wherever you like.
- So for example if you’re running a marathon with a big hill half way through, you can allow for that by using the +15 / -15 second toggles on the relevant mile splits.
- Then you can create your own personalised pacing band to wear during the race – simple!
And if you want to, you can even start from the ARU data to select a pacing profile based on a group of runners similar to you in experience and age, who you think paced their race well. You can view and tweak the data as your own pacing plan. You might not like the idea of using existing real data, and we’re not necessarily recommending this as an approach – our aim is simply to equip you to use the data in whatever way you like.
Go straight to the Marathon Pacing Calculator.
Skip back to revisit
PART 1: New Research Investigates the Challenges of Good Pacing