Learn how your body adapts, recovers, and thrives through the ultramarathon challenge.
Running an ultramarathon is one of the most extraordinary challenges a person can take on. With distances surpassing the traditional marathon’s 26.2 miles, ultramarathons push your body and mind far beyond what you thought possible. Every mile, your body undergoes astonishing changes to keep you going.
These events aren’t just physical; they reflect the adaptability and resilience of the human body. Let’s explore seven unbelievable things that happen to your body during an ultramarathon.
7 Things That Happen to Your Body in an Ultramarathon
1 – Your Muscles Break Down and Rebuild Stronger
Running for hours on end takes a toll on your muscles. Every stride causes tiny tears in your muscle fibers, particularly in the legs. This process, called muscle breakdown, can result in soreness, stiffness, and fatigue during and after the race. For ultramarathoners, this breakdown happens on a much larger scale compared to regular runs.
The good news is that this is a necessary step for growth. When the race ends, your body goes into repair mode. Muscle fibers are rebuilt, not just to their original state, but stronger and more resilient. This is why ultramarathon training is carefully structured with rest days and recovery weeks—to allow your muscles to adapt and become more efficient.
For recovery, ultrarunners rely on protein-rich foods, stretching routines, and techniques like foam rolling to ease soreness. Massage therapy and compression gear also help accelerate muscle repair.
Key takeaway: With proper care, the stress on your muscles turns into a strength-building process that prepares you for future challenges.
2 – Your Heart Becomes a Powerhouse
The heart is the engine that drives your ultramarathon performance. During a race, your heart rate increases to pump oxygen-rich blood to your muscles. Over time, the demands of endurance training cause significant adaptations in your cardiovascular system.
One of the most fascinating changes is the enlargement of the heart’s chambers, especially the left ventricle. This allows your heart to pump more blood with each beat, making it more efficient. Over time, this adaptation enables you to sustain intense physical activity for longer periods without fatiguing as quickly.
However, during an ultramarathon, the prolonged strain on your heart can temporarily reduce its efficiency. This is why recovery is crucial post-race. Rest, hydration, and light movement allow your heart to return to its baseline and prepare for the next challenge.
Pro tip: Monitoring your heart rate during training and races can help you optimize performance while avoiding overexertion.
3 – Your Body Becomes a Fat-Burning Machine
One of the most amazing adaptations ultrarunners experience is the body’s ability to switch energy sources during prolonged exercise. Typically, your body relies on glycogen (stored carbohydrates) for quick energy. But in an ultramarathon, glycogen stores are depleted after a few hours, forcing your body to shift to fat metabolism.
This process, known as ketosis, is a survival mechanism that allows the body to keep functioning even when carbohydrate reserves run out. Ultramarathon training often includes long, slow-distance runs to teach the body to burn fat more efficiently.
Why is this important? Fat provides a much larger energy reserve than glycogen. For endurance athletes, this shift is essential to sustaining energy over hours—or even days—of running.
Fueling tip: Ultramarathoners consume a mix of carbohydrates and fats during the race to support both energy systems. Gels, energy bars, and nut butter packets are common choices.
4 – Your Kidneys Work Overtime
The kidneys play a vital role in maintaining balance during an ultramarathon. They regulate hydration, filter toxins, and manage electrolytes. However, during extreme endurance events, the kidneys face significant challenges.
As blood flow is redirected to working muscles, the kidneys may receive less oxygenated blood. This can result in a temporary reduction in kidney function. If hydration isn’t properly managed, this can lead to dehydration or, conversely, overhydration—a dangerous condition known as hyponatremia, where sodium levels in the blood drop too low.
To support kidney health during a race, ultrarunners need to strike a careful balance between hydration and electrolyte intake. Sipping water regularly, combined with electrolyte supplements or sports drinks, can help maintain this equilibrium.
Warning sign: Dark urine or swelling can indicate issues with kidney function. If these symptoms occur, slowing down and rehydrating is critical.
5 – Your Hormones Go Haywire
Ultramarathons place incredible stress on the body, and this stress extends to your hormonal system. Cortisol, the body’s primary stress hormone, is released in large amounts during prolonged endurance events. While cortisol helps mobilize energy and manage inflammation, elevated levels over long periods can suppress your immune system and leave you feeling drained post-race.
For women, ultramarathons can also disrupt the menstrual cycle due to hormonal imbalances caused by physical and emotional stress. This condition, known as exercise-induced amenorrhea, is common among endurance athletes. It’s a reminder that adequate fueling and recovery are vital, especially for women taking on extreme distances.
Recovery strategy: Incorporating rest days, consuming anti-inflammatory foods, and managing stress can help regulate cortisol levels and support hormonal balance after an ultramarathon.
6 – Your Brain Plays Tricks on You
Sleep deprivation, physical exhaustion, and mental strain can lead to surprising effects on the brain during an ultramarathon. Many runners report experiencing hallucinations, especially during overnight races or multi-day events. These can range from seeing imaginary figures to hearing non-existent sounds.
Beyond hallucinations, decision-making and coordination can become impaired as fatigue sets in. Navigating trails or pacing yourself can feel increasingly challenging as the miles add up.
On the flip side, ultramarathons can also unlock a unique mental clarity. Many runners describe entering a meditative state, where their focus sharpens and they feel deeply connected to the present moment.
Mind over matter: Training your mind through visualization, mindfulness, or mantras can help you overcome mental hurdles and stay focused during the race.
7 – Your Immune System Takes a Hit
The physical stress of an ultramarathon doesn’t just affect your muscles and hormones—it also impacts your immune system. After such an intense effort, your body may experience a temporary drop in immune function, making you more susceptible to colds or infections.
This suppression occurs because the body prioritizes recovery and repair, diverting resources away from the immune defence. While this is a natural response, it highlights the importance of post-race care.
Recovery tips:
- Eat antioxidant-rich foods like berries, leafy greens, and nuts to reduce inflammation.
- Prioritize sleep, as it’s essential for immune system repair.
- Avoid large crowds immediately after a race to minimize exposure to germs.
The Mental Game of Ultramarathons
Running an ultramarathon isn’t just a physical challenge—it’s a mental marathon as well. Pushing past discomfort, fatigue, and self-doubt requires immense mental strength. Runners often adopt techniques like positive self-talk, visualization, and mindfulness to keep their minds focused and motivated.
Many ultramarathoners say that finishing a race is 90% mental. It’s about finding that inner voice that says, “I can do this,” even when your body feels like giving up.
Why it matters: Building mental resilience on the racecourse can translate into greater confidence and perseverance in everyday life.
Training Smart: Preparing for the Distance
Preparation is the key to a successful ultramarathon. Building endurance, practicing nutrition strategies, and incorporating rest days are all essential components of training. Gradually increasing your mileage ensures your body adapts without risking injury.
Don’t forget the power of cross-training! Activities like cycling, swimming, or strength training can enhance your performance while giving overworked muscles a break.
Pro tip: Investing in quality gear, such as moisture-wicking clothing and supportive footwear, can make all the difference during long runs.
Final Thoughts
An ultramarathon is more than a test of physical endurance—it’s a journey of self-discovery. The body undergoes incredible changes during these races, showcasing its adaptability and strength. From muscle breakdown and fat-burning adaptations to hormonal fluctuations and mental resilience, every mile teaches you something new about your capabilities.
While the challenges of ultramarathons are undeniable, the rewards are equally profound. Crossing the finish line of an ultramarathon isn’t just about physical achievement—it’s about overcoming mental barriers, embracing discomfort, and proving to yourself that you’re capable of more than you ever imagined.
If you’re looking for resources to enhance your training, nutrition, or mental game, visit PositiveKristen.com and PowerofPositivity.com. These platforms provide tools and insights to support your ultramarathon journey—and beyond!
