🏃🏽‍♀️ This is Your Body After a Marathon

Training for a marathon is hard work. Running a marathon is hard work. But anyone who’s ever crossed the line after 26.2 miles also knows that the hard work isn’t over when you stop your watch. At that point, the hard work of recovering is just beginning.

And, sure, we all expect that we might be walking downstairs backwards or sideways for a few days…and the toilet seat just feels so far away. The muscle damage is real–and it can take longer to recover from after 40. 

But here's what's gotten less attention: a marathon doesn't just wreck your legs. It temporarily stresses your kidneys, your gut, your immune system, and — new research shows — your brain (which, let’s face it, most of us who’ve done the distance, could’ve told you). And as women in midlife, we have some extra recovery considerations that the standard "take a week or so off" advice doesn't account for.

Since marathon season is in full swing, it seems like a good time to get into it.

It’s a Bit of a Kidney/Gut Punch

A study published last year out of the Boston Marathon found that virtually everyone — regardless of age, sex, pace, or hydration — showed signs of organ stress after 26.2 miles. Among 72 runners (average age 50, evenly split between men and women): 88% exceeded the clinical threshold for acute kidney injury risk, 96% had a creatinine spike that would "ring alarm bells" in a clinical setting, and 75% showed measurable damage to gut cells. When the intestinal barrier gets disrupted like this, bacterial endotoxins can leak into the bloodstream and drive systemic inflammation — making everything else harder to recover from.

Interestingly, about the kidneys specifically: recovery isn't linear. A Frontiers in Physiology study that tracked runners for eight days post-marathon found that kidney filtration rate appeared to normalize at 24 hours — then worsened again at 48 hours before finally recovering around day 4 to 8. That biphasic dip may be why so many runners feel okay on day two and then crash on day four.

Your Brain Literally Ran on Fumes

Some eye-opening research explaining why your brain feels like it’s stuffed with cotton balls post-marathon came from a small study published in Nature Metabolism. Researchers used MRI to scan runners' brains before and after a marathon and found that myelin — the fatty sheath that insulates your neurons and keeps signals firing cleanly — was measurably reduced in 12 brain regions after the race.

The researchers hypothesize that when glycogen stores run out, the brain may dip into myelin lipids as an emergency fuel source. The affected areas govern motor coordination, sensory integration, and emotional processing — which tracks with the post-race fog, emotional flatness, and shaky legs that have nothing to do with muscle soreness (though the researchers didn’t assess cognitive function).

The study found that myelin had substantially recovered by two weeks post-race and was fully restored within two months. The researchers stress that running marathons is not harmful for the brain; “on the contrary, the use and replacement of myelin as an energy reserve is beneficial because this exercises the brain's metabolic machinery,” said researcher Carlos Matute in a press release. 

Help Your Body Heal Up

Obviously, your body is gonna need a little time to recover from all that. You can help nudge the healing process along with a little TLC. Along with some light recovery activity to keep the blood moving over the following week:

Eat. Eat. Eat.  You’ve just drained your energy stores (including from your brain!), damaged your muscles, and pummeled your organs. It’s time to give them the fuel and nourishment they need to restock and rebuild. Focus on complex carbohydrates to restock depleted glycogen, protein to rebuild muscles, and anti-inflammatory foods like fatty fish and fresh produce to soothe joint and muscle stress. 

Importantly, muscle protein synthesis — the process that actually repairs the microscopic damage from 26.2 miles — requires a bigger protein signal than you might expect, and that threshold goes up after 40 due to anabolic resistance. Older muscles become less responsive to protein's repair signals, meaning you need more to get the same effect.  

A small trial on women aged 48+ found that 40 grams of high-quality protein along with 30 grams of carbs immediately post-exercise had a meaningfully better effect on muscle function recovery at 24 hours compared to the standard 20-gram (plus carbs) dose — and 20 grams showed no clear advantage over a carb-only recovery drink. Leucine-rich sources (whey protein, chicken, salmon, Greek yogurt) drive the response most effectively. Aim for that 40g dose within 30–60 minutes of finishing, then repeat every 3–4 hours for the first 24–48 hours.

Watch your iron. The repetitive foot impact of marathon running causes a mechanical breakdown of red blood cells — foot-strike hemolysis — that depletes iron stores. Up to 48% of female marathon runners have clinical iron deficiency. Standard blood panels can look completely normal while ferritin (your storage iron) is critically low, with real impacts on energy, mood, and recovery speed. If your fatigue isn't resolving after two weeks of solid rest and nutrition, ask your doctor for a full iron panel including ferritin — not just hemoglobin.

Sleep. Sleep is recovery tool #1. Deep sleep is when growth hormone peaks, and growth hormone is your primary overnight tissue repair signal. Poor sleep after a marathon doesn't just make you tired, it also directly impairs the recovery you're trying to accomplish. If you have hot flashes disrupting your sleep, it’s well worth addressing them for proper recovery–and long-term health.