Your Liver & Kidneys: The Ultra Runner’s Hidden Recovery System
When you run 50 or 100 miles, your legs aren’t the only things working overtime. Your kidneys and liver are working behind the scenes to keep your body functioning, processing waste, balancing fluids, and supporting recovery. Taking care of these organs should be part of every ultra runner’s plan.
Long races can place significant stress on the kidneys. Dehydration, heat, reduced blood flow, and prolonged exertion can all contribute to temporary changes in kidney function.
The answer isn’t simply to drink as much as possible. Overhydration can also be dangerous. Instead, practice your hydration strategy during training. Consider your sweat rate, weather, effort level, fluid intake, and sodium needs.
Your goal is to arrive at the finish line hydrated—not dehydrated and not overhydrated.
This is one of the biggest lessons for ultra runners.
Ibuprofen and other NSAIDs can interfere with prostaglandins that help maintain blood flow to the kidneys. During prolonged exercise, especially in heat or when dehydrated, that can increase kidney stress. One review of severe exercise-associated kidney injury cases found that NSAID use was common among hospitalized cases.
That doesn’t mean you should never use medication. It means routine or preventive NSAID use before or during an ultra deserves serious caution and discussion with your healthcare professional.
The liver plays a major role in metabolism, energy management, and processing substances your body needs to eliminate.
After an ultra, blood tests may show elevated AST and ALT. That does not automatically mean your liver is damaged. These enzymes can also come from skeletal muscle, which is heavily stressed during endurance events. Looking at other markers, such as CK, GGT, ALP, and bilirubin, can help healthcare professionals determine where the elevation may be coming from.
Your best recovery strategy is simple: eat enough, replace fluids and electrolytes appropriately, and give your body time to recover.
Heat can turn a difficult race into a medical emergency. Severe heat stress can reduce blood flow to the digestive system, damage the gut barrier, and contribute to a systemic inflammatory response.
Learn the warning signs: headache, dizziness, nausea, weakness, confusion, or unusual behavior.
If heatstroke is suspected, rapid whole-body cooling and emergency medical treatment are critical.
Pain is information. During an ultra, medications that reduce pain or alter your perception of discomfort can potentially hide warning signals from your body.
Acetaminophen (Tylenol) is different from NSAIDs, but excessive dosing can cause serious liver injury. The combination of prolonged exercise, dehydration, fasting, illness, or alcohol can make medication decisions more complicated.
Never exceed the recommended dose, and talk with your healthcare professional about what is appropriate for you.
After a long race, your body needs building blocks—not a “detox.”
Focus on whole foods containing carbohydrates, protein, healthy fats, fruits, vegetables, fluids, and appropriate electrolytes. Carbohydrates help replenish glycogen, protein provides amino acids for repair, and adequate fluids support normal kidney function.
Your kidneys and liver work hard enough during an ultra. Give them the nutrition, hydration, and recovery time they need afterward.
For more conversations about ultra running, nutrition, recovery, heart disease, training, injuries, and becoming a stronger endurance athlete, listen to Running Miles with Heart Disease CHD. I share real experiences, practical strategies, and conversations with experts to help runners go farther while taking better care of their bodies.
1. Protect Your Kidneys With Smart Hydration2. Be Careful With Ibuprofen and Other NSAIDs3. Don’t Forget Your Liver4. Respect Heat5. Think Twice Before Reaching for PainkillersRecover With Real Food
