My postulate to why Jakob won't improve as much as El Guerrouj or Bekele past 19? Because Jokob is already running fast times at 19. As simple as that. He is already developped physically and you don't improve fast after that. Some people mature earlier than others and Jakob has alway been an early bloomer. Kejelcha and Barega ran much quicker time at similar age and have not make further progress in times. They have made progress in the ability to run more and be more consistant in races. But not in overall times.
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I am not answering because I think I can convince YOU of anything. But since so many people on these pages for so long time have claimed that Jakob is about to peak soon I think it is of general interest to scrutinize your arguments:
A. Already running fast times at 19!? Should that be an argument for early peaking? Initially I will say that fortunately Steve Cram, K. Bekele and Alan Webb did not know this.
Cram held the 17 age WB in the mile for 39 years at 3:57.42. He ran 3:46.32 when 24!
Bekele was U20 WR holder in 3000 m at 19 running 7:30.67. He ran 7:25.79 when 24!
Webb was the fastest highschool miler at 18 running 3:53.43. He ran 3:46.91 when 24!
But in general: Why should being a very good teenager cause that you peak early? Isn´t - just as you say - a POSTULATE? And I will add without a supporting argumentation.
B. Then you add that he will peak early because he is an early bloomer. I acknowledge that this statement is a real argument. I, however, think that the statement is wrong:
a. I don´t think that Jakob is very early developed. I think he is average for a boy from Northern Europe. I am not sure he can grow a beard yet. I am myself from Northern Europe (not Norway) and I can remember that the early bloomers in highschool fancied beards, moustaches and whiskers but I don´t think Jakob can yet. He is possibly just about to finish growing.
Further I don´t think that he is developed earlier physically than the likes of Cram, Morcelli, El-Guerrouj, K. Bekele, Alan Webb and other toprunners who has improved up into their twenties and even their thirties, see more below.
b. I don´t think that a man is in his prime immediately after finishing growing. He has some years before he at his best regarding speed and physical strength. Sprinters normally don´t peak before in their early twenties. Many much later.
C. Here comes the most important argument against your postulate.
a. If an athlete (it is not only runners) trains aerobically which a longtime view without overtraining ( with a good mix of hard and soft days) he can develop his aerobic capacity for many, many years.
That is why the likes of Kipchoge and Bekele are able to set WR/ PB in their mid thirties in the Marathon. Performances in the marathon are almost solely determined by the athletes aerobic capacity.
Regarding Jakob: Why should Jakob be different? Why shouldn´t he be able to increase his aerobic capacity up into his thirties as well. Meaning that he will lower his times on the track from 1500m and upwards since the aerobic capacity is an important part the performance on these distandes too; the longer distance the closer correlation. And he can lower the times at least as long as he in his prime or close to the prime.
b. Some have claimed that Jakob will peak or even burn out soon because he has trained for so many years. It is true that he has trained in some way almost from the time he started in school being already VERY good aerobically at 10 (running 8km in 30 minutes) and that he started training systematically like his older brothers (but at an reduced mileage) at 13.
But should that really matter?
Gebrselassie, K. Bekele, Kipchoge, Mo Farah, Bernhard Lagat, Marcin Lewandowski and many more have trained much longer and still being able to set WR/ PBs in their thirties.
c. More statistics:
I have checked the all time toplists in the 1500m, 3000m and 5000m.
Africans some times peak early around 20 and some few before.
But runners of European origin including immigrants i The Americas and Oceania almost never peak before earliest in their mid twenties and most even later.
In the 1500m I can only find Jim Ryun (peaked at 19) and Ryan Gregson (peaked at 20).
In the 3000m and 5000m the youngest peaker of European origin is -as far as I can see - Craig Mottram at 24.
So why should European Jakob peak earlier than in his mid twenties? When his training seems to be almost the optimum aerobic exercise with a mix of of rather intense treshold repetitions followed by days with long recovery runs.
JAKOB´S OLDER BROTHERS HENRIK AND FILIP BOTH SET PB IN THE 5000M LAST YEAR AT AGE 28 AND 26 RESPECTIVELY. And Henrik also in the 3000m. They set PB in the 1500m at 23 and 25 respectively.
And I think they most likely improve futher! Just a confirmation that their well balanced aerobic training works!
Why do you compare Jakob with Barega and Kejelcha?
It is true that these 2, and you can include Gebrhiwet, have had difficulties to replicate earlier performances .
Barega his amazing 5000m PB in 2018.
Kejelcha his 3000m and 5000m PB also in 2018. Kejelcha had run almost same time 2 year before in 2016.
And Gebrhiwet who ran a very fast 5000m already when 18 and first at 24 broke this time with a couple of seconds.
On the other hand Jakob has improved every single year for many years in the 1500 (from age 12) and from 2016 in the 5000m so Jakob is the stable one! That is quite natural considering he is steadily heightening his aerobic foundation year after year.
So who do you think is most likely to plateau soon? Jakob or the Ethiopians?
Finally: Jakob´s performances doesn´t variate as much as fore example Barega´s and Kejelcha´s! Even in the races where Jakob is not at his very best he is still not far from his PBs.
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Are you ready to come back to this thread at the end of the season and comment on your statements as per now?
I promise to came even if my positive predictions don´t hold.