During 2001 training camp, Vikings lineman Korey Stringer died at age 27 from exertional heatstroke. In the aftermath, new protocols and a psychological pivot changed football.During 2001 training camp, Vikings lineman Korey Stringer died at age 27 from exertional heatstroke. In the aftermath, new protocols and a psychological pivot changed football.Read Morewww.espn.com – NFL