If your lower back starts screaming during a long run, you're not alone—fatigue is usually the culprit. According to Dr. Theresa Marko, a physical therapist specializing in orthopedics, those fast-twitch muscle fibers that kickstart your run eventually burn out, leaving your deeper, slow-twitch muscles to pick up the slack. And when those stabilizing muscles get overworked? Hello, lower back ache.
The Science Behind Running and Back Pain
Dr. Marko breaks it down like this: Your fast-twitch muscles are the sprinters of your body—powerful but quick to tire. They handle the initial burst of energy when you take off. But after a few miles, they start tapping out, and your slow-twitch fibers (the endurance athletes of your musculature) take over. The problem? These deeper muscles aren’t just responsible for keeping you moving; they’re also crucial for stabilizing your spine. When they’re overworked from compensating for tired fast-twitch fibers, your lower back ends up bearing the brunt of the strain.
Weak Core? Blame Your Hips (And Vice Versa)
Here’s where things get interesting—or frustrating, depending on how you look at it. A lot of runners assume lower back pain means their core is weak. And while that might be part of the issue, Dr. Marko points out that weak hip muscles often share the blame. "Your glutes and hip flexors play a huge role in maintaining pelvic stability," she says. "If they’re not doing their job, your lower back muscles end up overcompensating." Translation: Even if you’ve been religiously doing planks, skipping hip-strengthening exercises could still leave you wincing mid-run.
How to Prevent the Ache Before It Starts
Good news: You don’t have to resign yourself to post-run back misery. Dr. Marko recommends a two-pronged approach—strengthening and stretching. For strength, focus on exercises that target both your core and hips, like clamshells, glute bridges, and dead bugs. And don’t forget dynamic stretches before your run (think leg swings and hip openers) to prep those muscles for action. Static stretching post-run can also help ease tension in your lower back. Pro tip: If you’re logging serious mileage, consider adding a resistance band routine to your cross-training days to keep those stabilizing muscles in fighting shape.
When to Worry (And When to Just Roll It Out)
Not all back pain is created equal. If your discomfort is mild and fades after a rest day or some foam rolling, it’s likely just muscle fatigue. But Dr. Marko warns that sharp, persistent pain—especially if it radiates down your legs—could signal something more serious, like a herniated disc or nerve irritation. In those cases, it’s time to hit pause and see a pro. Otherwise, tweak your routine, listen to your body, and remember: Even the most seasoned runners deal with this. It’s all part of the grind.
Bottom line? Lower back pain during long runs is common, but it doesn’t have to be inevitable. Strengthen your hips, stretch smart, and know when to seek help. Your future self (and your back) will thank you.
