I used to love running, and even in those days I don't think I would have been able to do 2.4km in 12 minutes - never mind with a pack on my back! My fastest time on Strava is 9.14 mins for 1km. I've never been a fast runner, and I used to be ecstatic if I managed a 10km run in less than 60 mins.
What I do notice is that I'm always relatively slow to start, and if I pace myself at the start and don't go too fast (whether I'm running or climbing a mountain) my overall speed is faster than if I set off too quickly. I'm not a sprinter, unlike my sister, who has always been fast over a short distance, but is slower in distance running.