Stylish - my training as usual had been suboptimal, and the mileage pathetic, but I tried to keep all long runs in and ran 3 x per week. I think the improvement on my previous marathon time was due to strength training - I also recovered quite quickly with minimal DOMS.
This research has not been published in peer reviewed journal yet, but presented at a conference. As I understand it it's based on self-reported data, which is good for the numbers of participants but perhaps not as robust as having the data verified by actually examining the study participants by doctor/researcher.
Interesting that the author of the study is very clear about not being able to draw any definitive conclusions, but that never stopped the tabloid (or broadsheet) journos before..