Slowing down to run farther seems obvious, but it is the hardest thing for people to force themselves to do when they first attempt longer runs. To explain this, I’m going to target people who’ve never exceeded the 3-5 mile run range, think anyone going farther is crazy, and probably genetically superior.
Take your average high school athlete that has had to run 1-2 milers to stay in shape and maybe was able to crank out a 5 miler or 10k at one point for a charity race. This likely seemed like the hardest thing on their body because they were trying to keep the 1-2 mile pace over the longer distance. The fact is your body cannot maintain the heart rate you get up to when running a fast 1 mile over the course of 5 miles.
To show this point I’ve plotted the world record paces for the Olympic distances along with the mile and both full and half marathons:
Assuming that the average person would exhibit this rate of slowdown, someone who could run an 8 minute mile would be able to run a:
5k (3.1 mi) at a 9.1 min/mile pace (multiply by 1.13),
10k (6.2 mi) at a 9.4 min/mile pace (multiply by 1.17),
Half Marathon (13.1 mi) at a 9.6 min/mile pace (multiply by 1.20),
Marathon (26.2 mi) at a 10.6 min/mile pace (multiply by 1.33)
By slowing down at these rates for longer distances and periods of time, the body avoids crashing like when you finish a hard sprint and need to immediately stop to catch your breath.
There are a number of methods out there to determine your body’s thresholds like heart rate training and VO2 max determination, which I highly recommend looking into if you’re training for 13+ mile events. If you’re not a competitive runner and sticking to 10Ks or less the best thing is to listen to your body; it’ll tell you when you can pick it up and when you should slow down.
If you’re not consistently running and try this approach a few times a week you’ll be amazed at how easy it becomes to get up to 45 - 60 minute workouts. You’ll quickly be at a cardio level recommended by most doctors and medical journals. If you get the bug and want to push it longer or harder I would advise researching nutrition management to ensure you’re replacing adequate calories and fluids to keep you going and avoid serious injuries.
That’s my approach to running farther: slow down. I’d be curious to hear if any of you have found other methods that have really helped when trying to go from short to long distance running.