It’s long been believed that, if you over pronate, you’re more likely to suffer a running injury. That’s why we have so many motion control shoes with so many types of plastic, dual density foam and other materials to control our pronation.
What a typical runner’s progression might look like
In the spring of 1996, I lowered my 5K PR from 17:06 to 16:08 in two races. Afterward, I could consistently run in the low 16s. However, lowering that PR just wasn’t happening for the remainder of that track season or the 1997 season.
Then, after a year away from track for reasons that had nothing to do with running, I returned in the spring of 1999 and progressively worked my PR down to 15:43. Sub-16 became routine. I took my 10K PR from 34:12 to 32:57 in a single race. A mid-33, a short time earlier over 30 seconds faster than my PR, would now be a bad race.