I've run marathons and I am pretty sure I could not do this: 12 1/2 mile march in combat gear, no more than 5 hours while hauling almost 90-pounds of gear, at

I've run marathons and I am pretty sure I could not do this: 12 1/2 mile march in combat gear, no more than 5 hours while hauling almost 90-pounds of gear, at nearly a 4 mph pace (almost a jog), rifle included