More than 23,000 of the men and women lined up in Hopkinton for the start of the 2019 Boston Marathon will be there having run under an age-specific time threshold in another marathon, which shows just how unremarkable qualifying for the Boston Marathon really is. And yet, if you ask any of the 500,000 Americans who will run a marathon this year (and many of the million-plus marathoners in other countries), qualifying for Boston - a ‘BQ’ - can be a bit of an obsession.

We leave the parking lot, riding side-by-side up a short stretch of fire road before cutting left onto a rock-strewn creek bed that climbed sharply. Making it to the top requires choosing a path that navigates boulders, gravel, damp leaves, and roots - and then executing. Gravel can spin; boulders may be insurmountable; leaves and roots are slippery when damp. The hill is steep enough that the wrong choice would bring me to a halt. I carefully select a good line and push forward, breathing hard.

In the 15 years I have practiced obstetrics, I have been the surgical assistant on hundreds of cesarean deliveries that seemed to me, at the time, to be unnecessary, and I’ve been the surgeon of record for a handful of unnecessary cesarean deliveries myself. I know firsthand how difficult it is for physicians, nurses, policy makers, and administrators, all of whom are well aware that the United States has a cesarean epidemic, to wrestle with it.

Practically anyone who decides to run a 5K could do it tomorrow. It’s 3.1 miles - an easy hour-long walk for the non-runner who wants to get out there and pin on a bib. I have two daughters who run, and one who doesn’t, and all three of them are at the starting line most Thanksgivings for an annual turkey trot.

One early afternoon in December, the Blue Line platform at State Street held a couple dozen adults, a few of us obviously awaiting a train to the airport based on the luggage we dragged. The other platform, across two sets of tracks, was desolate except for one man, positioned at the end of the platform where the front of his train would stop. It was surprisingly quiet - so quiet that the sound of a suitcase rolling along the platform reverberated through the concrete station. The quiet was suddenly punctuated by the automatic voice announcing when the next train would arrive.