This is a sequel to Gaining the Quicken Enchantment.
Once someone has gained the Runnark enchantment, they are granted the Runner title. This gives them the speed of an Olympian sprinter and the endurance of an Olympian marathon runner. However, after someone gains the enchantment of twelve Runnark, they become a Boltrunner.
Boltrunners, like regular Runners, have the speed and endurance of an Olympian runner. However, they have the advanced respiratory system of a Runnark (think bird lungs, but human-size) and move much faster. How fast, you ask? The average person walks at 3-4 miles per hour, but a walking Boltrunner will move at 30-40 miles per hour!
"Wait," you say. "Wouldn't that force them to eat an insane amount of food?" No, and that's where Boltrunners are game-breaking. Walking 30-40 mph for a Boltrunner takes as much energy for them as it would take the average person to walk 3-4 mph!
Now remember, each Boltrunner was once a regular Runner, who had the capacity to run at Usain Bolt speeds. Thus, the top speed of a Boltrunner should be about 270 miles per hour! This gets even more insane when one considers each Boltrunner has the ability to run at top speed for what would be 26 miles and 385 yards for a regular runner.
In other words, when a Boltrunner is done running at top speed, they'll have covered about 7,020 miles! I believe this will revolutionize the sharing of information in medieval Europe (the basis of my story's setting), since A) a Pony Express-type system could allow Boltrunners to quickly relay information over vast distances and B) faster couriers, faster information exchange.
However, my question is How Would The Quicken Enchantment Benefit Humans? because I want to know how the Quicken enchantment would benefit people, not just Runners, in the medieval period.
Specifications for Best Answer:
The best answer will first account for how useful Runners and Boltrunners will be as couriers. Remember, we're talking about medieval Europe.
The best answer will also account for the other uses of a Runner and Boltrunner's enhanced speed; the top and average movement speed of a Runner is enhanced so it's directly proportional to Usain Bolt's top and average running speeds. The same goes for a Boltrunner, which moves 10x faster than a Runner. This probably has immense military applications; it's hard to fight, shoot, or retreat from people who are that fast.
Finally, the best answer will account for how beneficial the Quicken enchantment will be on Runners and Boltrunners, not just for the people employing them.
One Last Note: Obviously, the Quicken enchantment reinforces its holders so they are not harmed by the effects of their own speed. Obvious exceptions would be if they slip, fall, or hit something hard at high speed, because slipping on an icy pond or hitting a boulder at 270 mph will have inescapable consequences!