Karl Metzer, the 42-year-old distance runner who is testing his endurance in Red Bull’s “Human Express” this month and next, crossed into Utah from Nevada over the weekend, bringing his total mileage past the 500 mark.

Meltzer is slated to run 2,300 miles of largely unpaved trail along the old Pony Express route from Sacramento, CA to Kansas City, MO.

According to Red Bull, Meltzer is averaging about 4 miles per hour, and about 50 miles and just 2,740 calories per day. His average heart rate is pegged at 99 beats per minute.

Global Rescue is providing medical evacuation coverage for Meltzer, with aircraft and ground transport on standby throughout the route in the event of a medical emergency.