Blummenfelt is a very special athlete. I saw him do a triathlon here in Australia as a 17 year old where he ran a 15:07 5k at the end of Sprint distance triathlon in 100 degree (37 celsuis) day. Now what was impressive is that he ran away from the top Aussie junior who ran 8:08 on the track for 3k just a few months prior. I suspect Blummenfelts VO2Max is very very high.