Study one, strength training prevent loss of stride length..OK...maybe relevant...maybe not. Second..soccer players..not endurance athletes. More of a stop and go sport. Third study a review in the Journal of Strength and Conditioning Research. It is an OK journal. I subscribe, but they have a large pro strength training bias. Not sure I would look there for a balanced review on the subject. Third study, core strength training. Not sure what they did.
Consistently what is found is that in some cases running economy can be improved with some strength training. Probably resulting from an increase in the elastic properties of the muscle (stiffer series elastic component). There is SOME evidence to support strength training for runners, but it is not overwhelming and most elite runners do not employ strength training regularly. Some include some in the off season. Rarely do they continue it into racing season.
For other sports like swimming and cycling, the research is much more consistent; strength training does not improve endurance performance.