To all those saying "He's not making enough money to be on drugs!", if he wins TNF in 11 days that will be Close to $15,000 in just three weeks/2 races (not including whatever bonuses he has on his Hoka contract).
He trains in Flagstaff, and has made insanely massive improvements in just one year. So we can roll our eyes at the track/roads but ultra-guys are just too "pure" to raise suspicion?
Oh come on, we all know PEDs are near impossible to obtain in Flagstaff. ;')
The lack of money argument is weak cheese. Those of us who have been around a while all all know endurance athletes who have used PEDs, and apparent lack of funds has never been a significant barrier. A good program designed to circumvent WADA type testing can be expensive I suppose, but there simply is essentially zero scrutiny of PED use in ultrarunning.
That said, I personally choose not to believe Walmsley is using PEDs. But it is naive to not at least critically and openly assess these kinds of stunning performance improvements.