CNN
 — 

Philip Kreycik should have survived his run.

In the summer of 2021, the 37-year-old ultra-marathon runner used an app to plot a roughly 8-mile loop through Pleasanton Ridge Regional Park in California, a huge stretch of parkland threaded with trails.

On the morning of July 10, as temperatures crept into the 90s, Kreycik set off from his car, leaving his phone and water locked inside. He started at a lightning pace — eating up the first 5 miles, each one in less than six minutes.

Then things started to go wrong. GPS data from his smartwatch showed he slowed dramatically. He veered off…