Lately, “strong” has been a one-word mantra for me. In workouts, it pushes me to go for another rep or add weight to the bar. In life, it gives me confidence to tackle challenging assignments and helps me stay grounded when my kid emerges from his bed for the 27th time. But today, my definition of “strong” was challenged.

This morning I attended a charity event for Lauren Bovis, a bone marrow recipient and woman in my running group—a woman who has shown more strength in the past several months than I’ve ever needed to in my life. The event consisted of a run, yoga class and the opportunity to sign up as a bone marrow donor through the organization Be the Match. After completing a strong run and feeling strong on my yoga mat, I stood at the donor table and read the pamphlet on bone marrow donation. I freaked out a little.

I’ve tried to donate blood once in my life. I got dizzy and turned white within seconds, so they stopped the process and sent me home. Ever since then, I’ve been afraid to try again. Obviously, donating bone marrow is much more intense. It is a surgical procedure that involves taking liquid marrow from your pelvic bone (there is only about a 1 in 500 chance that if you register as a donor, you will actually be called). Just the thought of this made me a little queasy. I looked around me. No one else was freaking out. Lauren was standing a few feet away, chatting with friends through her surgical mask.

Strong. I was surrounded by strong women, women who were wearing my one-word mantra on their sleeves.

I thought, “Come on Nicole, your body can run 26.2 miles and deadlift 150 pounds. Twice, you’ve carried a baby for nine months and had natural births both times. You’re strong enough to do this. Suck it up.”

Over the past few years I’ve learned to not take my body for granted, to appreciate what it can do more than how it appears. Our bodies can do amazing things, and here was another opportunity to prove it: to be strong not just for myself, but for someone else.

I thought about how I’d feel if I signed up to donate and got a phone call that I was someone’s match. I could save someone’s life, at the expense of a week or so recovery time on my part.

I grabbed a donor form and didn’t look back. Done.

My one-word mantra still stands, but it’s not just mine anymore. Don’t just be strong for yourself. Be strong for someone else.