More than 30,000 runners, representing a range of ages and fitness levels, are expected to amass at Central High School on Sunday morning for the Broad Street Run. I was excited to be among those who registered before the popular 10-mile run reached capacity in an unprecedented five hours.

My excitement, however, quickly gave way to anxiety. I am no elite athlete or seasoned runner; I am a suburban mother of four who started running less than a year ago.

For reasons that defy conventional wisdom and my own conservative nature, I picked up running at the age of 42, with four small, needy children underfoot. At the time, my youngest was 3. My eldest, a teenager, has severe multiple disabilities requiring extensive care.

As a busy stay-at-home mother, I had neglected my health for a long time, living off diet sodas, coffee, and junk food. I had not set foot in a gym, or done so much as a single halfhearted sit-up on my bedroom floor, for more than four years. Furthermore, I had not actually run in about three decades. Convinced that I loathed running, I had avoided it since retiring from my cross-country team at the age of 13.

And yet here I am in middle age, running. Loving running. OK, obsessed with running.

I'm not alone. The cohort of female runners — especially women between the ages of 35 and 45 — has increased dramatically in recent years. As of 2010, about 41 percent of American marathon participants were women, and the female presence in half-marathons was up to a solid majority — 59 percent.

My hypothesis is that something resurfaces in many women after years of sleepless nights, diapers, spit-up, and tantrums. We put so many of our dreams and desires on the back burner as we created and guided growing families. But once our children start school and become more independent, blocks of time and psychic energy begin to free up. Then it's as if all the time spent in the trenches of motherhood has made everything about us stronger, and we want powerful bodies to match our resilient souls.

If we lost ourselves under piles of laundry and dirty dishes, perhaps we're rediscovering ourselves while lacing up our shoes and covering eight miles by foot instead of crumb-encrusted minivan.

When I run, it's not an escape, but an act of determination. Every mile I cover feels like outer proof of my inner strength.

A year ago, I never thought I could run one mile, let alone 10. But on Sunday, I will be out there in the early-morning air on the corner of Broad and Somerset. I will be running with tens of thousands of others, each with a story to tell, and running for no one but me. Sixty-five thousand shoes will beat against the blacktop, and mine will be among them.

And I'll be a speck somewhere in the ribbon of bobbing heads and Under Armour cascading across the finish line — one middle-aged mom running slower than lightning, faster than her children cheering her on, and right on the heels of all I dare to be.

Alicia DiFabio is a writer who lives in South Jersey. Her blog is at http://welcometomyplanet4.blogspot.com.