It's not that Jakob is a slow twitch runner at all. He can close very well, 54 in a 4:50 top ten all-time 2k, 3:30 several times, and can close faster than most, but not as good yet as Tim or GWet, as proved a number of times. But that's the way he is being trained by Gjert. They just don't do a lot of high speed work. They're trained as miler/half marathoners. That is, the vast majority of the work, not including easy runs, is at half marathon pace or at best 10k pace, and then they do hill sprints, strides, and only do a limited number of mile race pace items during the late part of their season, ten days prior to Monaco and championships (10x300 at mile pace). Gjert yells at them if they run faster than mile pace, at least early on in that workout. So, to me, it is a great thing that he is running an 800m. In order to compete for gold, he has got to train that 800m time down to 1:44-43. That will allow him to run away from people with 400 to 600m to go, to avoid those with better top end speed like Lewandoski. The Ethiopians do a lot of top end speed work, as well as sprints in the course of their forest runs at 10000 ft. That pays off at the end of races. With milers not used to running 8s, it can take a few races to get their times down because they're not used to going out that hard. Steve Scott, for instance, only got down to 1:45.05 in his mile pr year. Alan Webb had a pr of over 1:46 as a pro for a long time, maybe even at the start of his wunderjahre of 2007 when he ended up running 1:43.84 and getting a twinge that hurt him at World's that year. So, maybe he runs low 1:46 or high 1:45 first time out this year and then eventually gets down to 1:44 this year and 1:43 in a year or two.