Speed hiker and ultrarunner Mikhail "Misha" Popov died last week of heatstroke following a solo training run in Death Valley, California. He was 34. On Tuesday morning, he drove to West Side Road with his partner, Sarah Spelt, to complete a six-mile solo training run to Badwater. Spelt said she regretted not being able to talk him out of the route, which he didn't start until noon. "I said, 'Mish, you can't try to get across here.' I pictured him stranded in bushes in the heat, stuck, dying. I just can't get over that I didn't just slap him and make him listen to me." Popov ended up misjudging his route, lengthening his time in the 123-degree heat. When paramedics arrived, they were unable to revive him. Popov was well known for breaking the speed record for the 222-mile John Muir Trail in 2007, hiking it unassisted in 4 days, 5 hours, and 25 minutes.