Try boosting your weekly mileage by about 20 percent over the course of 4 to 6 weeks. The extra mileage shouldn't be difficult. If you're wondering, the majority of your runs should be easy runs.
Add a mile or two to your long run as well, remembering that "long slow distance" isn't always the best way to run these. Try running the last 3 to 5 miles at a moderate pace (15 to 30 seconds faster than your easy pace), or surging for 30 seconds to 1 minute every 4 minutes during the last few miles.
These varied long runs don't have to be too structured, but doing a little bit of fast running during the second half of a long run produces fantastic endurance adaptations.
PR Principle #2: Speed Development
As well as gaining endurance, boosting your speed will also help to reduce your current 5K PR. But in addition to strides (which you should be doing 2 to 3 days per week), what else can you do to improve your ability to run faster?
A more advanced version of regular 'ole strides are hill sprints, which are shorter, faster and run up a steep hill. Remember these basics:
- Start with 2 to 4 hill sprints lasting only eight seconds each
- Run the first one at 95 percent maximum speed, while the rest are at 100 percent effort (yes, you'll be going as fast as you possibly can)
- Find a very steep hill, one that you would normally avoid for regular hill repetitions
- Take a full 1 to 2 minutes of walking recovery in between each one. Don't rush these
- Run hill sprints after an easy or moderate run, 1 to 2 times per week
- Build to 6 to 8 reps that last 10 seconds each
Hill sprints have a host of benefits, including injury prevention (once you get used to them), enhanced stride power, improved running economy and efficiency, and a better ability to recruit more of your fast-twitch muscle fibers.