No I just think much like Jakob's current 800m PB is 1:49 but he has run 3:30 in the 1500m, Jakob will continue to infrequently race the 800m. This will mean he doesn't get much practice at the event, and with his lack of basic speed will not get the opportunity to break 1:45.
Henrik is 29. His PB is 3:31 and his 800m PB remains at 1:48.
Filip is 27. His PB is 3:30.01, the fastest of them all. His 800m PB remains at 1:47.8.
Basically, Gjert doesn't have them race the 800 often, doesn't do the speed or lactic work required. The focus of their training is on endurance. He clearly doesn't see the value of the 800 for the 1500m or he doesn't care about it. That's probably not gonna change.
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You can´t compare Jakob´s 800 PB at 16 with his 1500m PB at 18! At 16 Jakob ran 3:40 in the 1500m!
You can´t compare Jakob with Henrik and Filip since Jakob (also in the 800m) has been so much better that his older brothers. As Jakob has been much better than almost all toprunners according to the following statistics (note that I have added a number of runners to my earlier post!):
Steve Ovett. age 17 1:47.34; age 22 1:44.09
Seb Coe. age 20 1:44.95; age 24 1:41.73
Steve Cram. age 20 1:46.29; age 24 1:42.88
El-Guerrouj. age 20 1;47.18
Marcin Lewandowski. age 17 1:51.73; age 19 1.46.69; age 28 1:43.72; age 32 1:43.74
T. Makhloufi. age 21 1:49.40; age 28 1:42.61
Centrowitz. age 20 1:51.40; age 25 1:44.62
Elijah Manangoi. age 22 1:47.40; age 25 1:44.15
Craig Engels. age 16 1:55.37; age 19 1: 51.03; age 25 1:44.63
Jake Wightman. age 18 1:52.16; age 19 1:48.01: age 24 1:44.61
Timothy: age 18 1:45.92; age 23 1;43.11
Kalle Berglund. age 16 1:58.39; age 19 1:46.85; age 22 1:46.63
Drew Hunter. age 16 1:59.55; age 18 1:48.64; age 20 1:48.57
Josh Kerr. age 16 1:53.80; age 19 1:48.05; age 21 1:45.35
Medhi Baala: age 17 1.49.62; age 19 1:49.71; age 23 1:43.15
Mo Farah: age 19 1:51.97; age 25 1:48.25
Souleiman. age 18 1:51.78; age 19 1:47.45; age 22 1:42.97
Iguider. age 17 1:49.65; age 19 1:48.00; age 28 1:46.67
Nick Symmonds. age 19 1:49.51; age 28 1:42.95
Duane Solomon. age 17 1:51.76; age 19 1:47.45; age 27 1:42.82
Henrik Ingebrigtsen. age 16 1:54.26; age 19 1:50.84; age 23 1:48.09
Filip Ingebrigtsen. age 17 1:54.65; age 19 1:50.52; age 23 1:47.79
Jakob Ingebrigtsen. age 14 1:52.60; age 15 1:51.07; age 16 1:49.40; age 19 ???
From this statistics you can at least conclude 2 things
1.Jakob was far better in his mid teens than almost all the above mentioned top runners. Only Ovett, Coe and Timothy seem to be close or better (even though we don´t know their early teen times)
2. Every single toprunner has improved significantly up into their twenties and some even into their late twenties.
And I will ask as before on these pages: Why should Jakob develop differently?
By the way: I think Filip could set PB with 1.5- 2 seconds tuesday. But I maintain that Jakob will run faster than Filip.