While cruising with a couple former high school cross country teammates on a long run recently, we chatted about everything under the sun. We reminisced on our teenage years, caught up on where we’re at now in our lives, and, of course, debated about super shoes and so-called “runflation.” (If only carbon-plated shoes had existed when we were in high school!) But then naturally, as runners often do, we dived into a conversation about races and our own running journeys. We started going back and forth about training philosophies—specifically for the marathon distance . Two of us three on the run had completed multiple marathons (myself included), so we quickly started bouncing ideas off each other. What’s the sweet spot for weekly training volume ? Can you run a fast marathon on 40 miles a week? How much is too much quality work? Are doubles necessary for building mileage? We shared what’s worked for our own builds, the tweaks we’ve made after setbacks, and the eye-opening lessons we’ve learned along the way.…