Yes, following on from lasts week's post where I used the data from this year's London Marathon to show that running a negative split is not an indication of a good performance, tonight I will hopefully provide an explanation into why the negative split doesn't work for non-elite runners.
In response to last week's post, and to previous pacing posts, I have received a number of comments. Thanks for the comments, it is nice to know that people are reading these blogs, and the blog is achieving its aim, of getting people to question / evaluate their ideas on running, in this case on pacing. Some of the comments I totally agree with, others have got me questioning why I believe my view that differs is more likely not to be wrong.
I guess the key issue, which many people have difficulty dealing with, is that if the negative split seems to work for the very very best in the World. i.e. the World recorder holders, then surely it should work for everyone. Below are two comments received.
"As I pointed out in my recent post about the folly of positive split, elite marathoners achieve their best performances by running negative or very even splits. This evidence screams out the small negative or even spits are best, but you just dismiss that somehow Elite's and non Elite's are somehow different because they train differently, and that somehow "magically" positive split becomes best." Robert.and
"No offence to hundreds of thousands of runners, but quite frankly I don't care that 95% of them run positive splits. The real question should be could they have run a faster time if they would have run more even splits? And again, who cares if it was even a PR - could that PR have been a better PR? I think this topic is very hard scientifically to prove physiologically...but I do think a big stack of correlated data is useful. If you look at the data and nearly all world records at all distances come from even to slightly negative splits, that has to mean something. Random middle of the pack people running positive splits to me only solidifies the point." Brett.How elite marathon runners manage to achieve a World record on a negative split, I don't know. However, what I do know is that for non elite runners, attempting to achieve an even split or a negative split in a marathon is not the right approach. I have provided the statistics to show this, e.g. 121 out of the first 122 finishers of the non-elite field at the 2013 London Marathon ran a positive split. But now is the time to explain why for non-elite runners, the positive split is the best approach.
Firstly, the argument for the even split strategy as provided within a comment left:
"Mathematically and energetically, even splits are best. If you do a negative split, then you will have been losing time in the 1st half of the race. A positive split and you'll be losing time in the 2nd. Fact. Additionally, any variation in pace will generally result in poorer running economy. Of course, things are never as simple as that and tactics, course and environmental conditions will all have an affect on what is the ideal pace" Andy.
Yes, on the face of it, if we look solely at the energetics of running, keeping a constant physiological intensity does appear to be the correct approach. The only problem is, that for non-elite marathon runners a constant running pace DOES NOT result in a constant physiological intensity. This is where the confusion lies! Now you will note that I again have used the term for non-elite runners. This is because I have been unable to find published material within the scientific literature that has data on elite marathon runners, in terms of how much the physiological intensity increases throughout the duration of the race, whilst running at the same pace. If anyone has got some literature on this aspect, please e-mail me the author names/title or provide a link within a comment.
So in paraphrasing/plagiarising Brett above:
"No offence to the elite runners, but quite frankly I don't care that the very very best of them run negative splits. The real question should be could I run a faster time if I would have not tried to run even splits? And again, who cares what the elite do if it was even a World Record - I am not an elite runner, I do not have the some time / resources / 'talent' etc, what do I need to do regarding pacing so that my marathon time could have been a better PR?"
So what do I mean by a constant running pace DOES NOT result in a constant physiological intensity? Lets look at some data.
First I will look at the following study: How Do Humans Control Physiological Strain during Strenuous Endurance Exercise? Jonathan Esteve-Lanao, Alejandro Lucia1, Jos J. deKoning, Carl Foster. This study monitored the running performance of 211 male middle and long distance runners with an average age of 32, and of various abilities. All trained for and entered competitions with the intent of achieving their best possible performances. Although not elite performers, all were serious competitors and some were successful in regional competitions. The average time for the marathon was 3 hours 01 minutes. The graph below displays how as the marathon race progresses, there is a continuous increase in heart rate, whilst at the same time there is a decline in running speed, starting at around the 20km mark, (ignoring the downhill section between 25-30km).
One explanation for increases in heart rate during endurance events is that it is a result of cardiovascular drift, and this is thought (not totally understood) to be due to a combination of dehydration, increased body temperature and increased sympathetic nervous system activity (e.g. adrenaline release). Whether the percentage increase in heart rate attributable to cardiovascular drift truly represents the same percentage increase in physiological intensity is debatable. Although the heart rate is increasing, the cardiac output (this being the amount of blood being pumped out of the heart every minute) may not be increasing, as the reason the heart rate has increased, is because the stroke volume (the amount of blood being ejected each heart beat) may have decreased. I'm trying to stay away from the actual causes of fatigue tonight, so won't comment on the relationship between the heart rate and the rating of perceived exertion, and how this relates to fatigue, as I am trying to solely focus on the physiology. But typically a rise is heart rate during a race means that the athlete is 'working harder'.
So if these 211 marathon runners wanted to maintain an even pace throughout the marathon, to avoid the decline in their running speed in the second half of the race, they would require an even more significant increase in heart rate during the second half. Already the heart rate has increased from around 85% of HRmax until half way, up to around 90% of HRmax at the end of the race, so most likely an increase in HR of around 8 - 9 beats per minute. To maintain an even pace for the second half of the race would require an even greater increase in heart rate, so as you can see, running an even pace DOES NOT result in a constant physiological intensity.
Just to get around the issue of whether the increase in heart rate does actually represent an increased physiological demand, if one wants to define physiological intensity as being represented by cardiac output rather than heart rate. Then looking at how cardiac output increases during a race would be useful. A recent study from 2012 did exactly this! Using some new technology they managed to record cardiac output of 14 middle-aged runners running in a real marathon race, with an average finish time of 3 hours and 50 minutes (so a slower group of runners than the previous study).. The study was titled: Cardiac Output and Performance during a Marathon Race in Middle-Aged Recreational Runners. V´eronique L. Billat, H´el`ene Petot, Morgan Landrain, RenaudMeilland, Jean Pierre Koralsztein, and LaurenceMille-Hamard.
Again, as the marathon statistics from the London Marathon showed, with 96% of runners positive splitting a marathon race, there was a continuous decline in running pace as shown in the graph below.
The graph also shows how even though pace has significantly decreased, the cardiac output has stayed pretty constant, maybe a slight increase. Again it is clearly obvious that if the 14 runners wanted to maintain a constant pace, i.e. run an even split, then there would need to be quite a significant rise in cardiac output. The authors of the paper have illustrated this in the graph below, where they have expressed heart rate, stroke volume and cardiac output in relation to per metre run, so in essence in relation to running at a constant speed.
I appreciate that these 14 runners have an average finish time of 3 hours 50 minutes, so some of these runners were achieving slower finish times than what many runners aim to achieve, so some people may question the 'value' of this data. In addition, the finish times had a standard deviation of 45 minutes, so a large range of finish times. The fastest time was 2:57, and the slowest 5:10, hence why there are large standard deviation bars on the above Figure 4. Taking into account this large variation in finish times, the researchers looked for any significant relationships between the physiological data and the marathon finish time. The following graph displays one of the key relationships found. This being that there was quite a strong relationship (r = −0.65, P < 0.01) between the upward drift in the Cardiac Output /speed ratio and finishing time.
When comparing between the elite and the non-elite, one must also remember that the duration of the race for the elite (with a finish time of a little over 2 hours) is on average around only half the finish time of the average runner. Therefore the average runner is running for double the amount of time! As the upward drift in cardiac output is continuous over time, then the longer the time of the event, the greater the drift will be, and hence in terms of the optimal physiological energetics, the further away the runner must then be from trying to achieve an even race running pace strategy.
Now lets go back to the message I was trying to get across in my last post, based on the data from 25,000 marathon finishers (< 5 hours) at the 2013 London Marathon, although I only looked in detail at the the first 11,000 finishers (< 4 hours). Still a pretty big sample size. The table below lists the percentage average percentage slowdown for six finishing time bands.
One must also look at the 14 subjects used in the study (middle-aged, male, recreational marathon runners all of whom were national-level short-distance triathletes or international level cyclists). It is therefore likely that due to not being marathon runners, their legs may not have been 'conditioned' to the pounding they get whilst running a marathon, as opposed to cycling. It is therefore likely that they may have experienced increased drift in cardiac output due to extensive damage and fatigue within the leg muscles. I am only speculating here, but leg muscle fatigue has been shown to have a large influence on marathon running performance. And with these 14 subjects being national level or international level, one would expect that aerobically they were very fit, so this excessive muscle fatigue could be a reason why the average finish time was only 3:50.
Anyway, regardless of the specifics of these 14 subjects, I hope that I have been able to illustrate above that in order to run at a constant even pace throughout a marathon, requires a progressive increase in physiological load, and therefore is contradictory to the even split physiological energetic argument often presented as to why the even split pacing strategy is optimal.
As I have just mentioned the issue of muscle fatigue, which has been shown is a key aspect with regards to marathon running performance, I'll expand of this aspect a wee it. A recent 2013 study (Running Pace Decrease during a Marathon Is Positively Related to Blood Markers of Muscle Damage. Juan Del Coso et. al.) that investigated muscle damage in 40 amateur runners with an average finish time of 3 hours 12 minutes, found that their leg muscle power, tested immediately after the marathon, had decreased by 17%. Interestingly the average percentage decrease in running pace was 16%. So clearly with marathon running inflicting muscle damage, with the muscle becoming fatigue, there is obviously going to be an increase in physiological load as the marathon progresses, and hence the upward drift in cardiac output.
Again, a bit of speculation, but perhaps due to the extremely high levels of training that the elite marathon runners are able to perform, due to being full time athletes, then perhaps their legs are more 'conditioned' and therefore they do not 'suffer' the same amount of muscle fatigue, and so do not encounter the same upward drift in cardiac output. Hence why it is not wise for the non-elite runner to try to 'mimic' what the elite runners achieve. Hence why trying to run an even split / negative split for the non-elite runner is simply foolish!
In terms of how foolish. What consequence will it have? Well lets say for a 3 hour 50 minute runner. with a percentage slowdown of 9:9%, which is the average for a runner of this finishing time, then this runner on average would slow down 11 minutes and 23 seconds during the second half of the marathon. So if they went out to go through half way in 1:55, they would miss their 3:50 target by on average a little over 11 minutes. If they had just gone out that little bit faster, rather than running totally comfortable for the first half of the race, they would only need to have reached half way in 1:49:35, less than 5 and a half minutes quicker, and they would achieve their target finish time of 3:50. By going out that little bit quicker, they are therefore able to slowdown their pace during the second half of the race, in order to keep the physiological intensity more constant , which is argued as the optimal strategy one should adopt.
Well, this post again has ended up being a bit longer than anticipated. However, hopefully I have helped explain why the even spit pacing strategy is not wise for non-elite runners. The fact that 96% of marathon runners positive split isn't because 96% of marathon runners are getting it wrong. It is because the concept of the negative split / even paced strategy is WRONG!
I am suggesting that due to the on average 5.1 - 9.9% slowing down of pace during the second half of the race, for a sub 4 hour marathon time. In order to counteract this, in reality this rather small amount of slowing down, the runner only requires a slight increase in running pace for the first half. By acknowledging this percentage slowdown, which takes into account the physiological responses that actually occur during a marathon, rather than some non-evidence based ideal of an even paced strategy, then there will be an increase in marathon runners achieving their goals, which surely must be a good thing!
I will sign off tonight again with the quote from Tom from Marathon Talk:
“My money's still on the even / negative split but I'd be delighted to be proved wrong. My quote for the day... I'd rather know I was wrong than think I was right ;)" Tom Williams, 2011.Hopefully after tonight's post, there is sufficient proof for Tom to stop encouraging the thousands of listeners to Marathon Talk to try to achieve an even split, or at worse a negative split.
All the best as you plan your pacing strategy for your next race,
PS I promise that this will be my last post on road marathon running. I will get back to trail running blog posts, so apologies to those trail runners out there that aren't interested in road marthons, and the emphasis on mile split times and finishing times.
Yes, UltraStu will return to trail running, and just as a taster, I received an e-mail from the Cotswold Outdoor Store asking if I could promote their newly released trail running video titled "Why I Run: A short trail running film". So to get back into trail running mode, here is the LINK to their video. Take a look as I 'm sure it will remind you, after all of this road running talk (not that you probably need reminding), of the joy of running on the trails.