What Happens to Your Body After a Marathon?

Running a marathon is undoubtedly strenuous on the body. And your biomarkers will likely sharply fluctuate in response.

This article outlines what post-marathon side effects to expect from your body and blood biomarkers after running long distances. We'll also share evidence-based recovery strategies that’ll help you feel strong and mended by your next starting line.

» Improve your health span through nutrition, supplements, exercise, and lifestyle recommendations

What to expect from your biomarkers post-marathon

Running a marathon certainly impacts how your body feels. But what actually happens internally?

During a race, the body goes into overdrive, depletes energy stores, breaks down muscle, and loses fluid and electrolytes. And afterward, it needs to recover from that damage. Measuring blood biomarkers after a long race can provide you with real data on your recovery status and explanations for specific post-marathon symptoms.

» Find out how biomarker tests unlock peak performance and how you can use this science to gain your own edge



Here’s the science behind four biomarkers impacted by a marathon.

1. HsCRP and inflammation

The biomarker hsCRP measures the body’s general inflammation levels and provides unique insight into athletic performance and recovery. It’s no secret that running a marathon can leave your joints and muscles inflamed. Continuous strenuous exercise can increase inflammation and cause markers like hsCRP to stay elevated. While some acute inflammation is necessary for the body to grow and repair muscles, uncontrolled inflammation can halt muscle gains. [1]

» Learn how to measure inflammation

Levels of hsCRP typically peak within 24 hours of intense exercise and can stay elevated for up to 7 days. One study investigated the impact of marathon running on blood biomarkers in 86 runners. Researchers found that 8 days post-marathon, hsCRP levels were still higher than baseline levels. [2]

» Determine if inflammation is affecting your training and recovery

2. Testosterone

Testosterone is a crucial hormone for male and female athletes alike. Testosterone is anabolic, meaning it triggers processes that build tissue and help it recover. This hormone impacts marathon performance—low levels of free testosterone are associated with improper recovery, impaired fitness gains, and increased risk of injury. It also stimulates red blood cell production, which is important for transporting oxygen from the lungs to muscle tissue. [3]

» Understand the science behind testosterone biomarkers

Markers like testosterone typically detail a longer-term view of how an athlete is handling a training cycle. If the training intensity is too high, race day can increase sex hormone-binding globulin (SHBG) levels—which almost always coincide with below-optimal levels of free testosterone. [4]

Going into a marathon with increased SHBG levels and decreased free testosterone can slow down post-marathon recovery. Studies show that training can increase testosterone levels, but testosterone levels may plummet after longer distances like a marathon. [5]

» Learn how to improve your testosterone levels

3. Cortisol

Cortisol, the “stress hormone,” increases in response to emotional and physical stress—like a marathon. This hormone is essential for short-term energy production to meet the immediate energy demands a marathon requires. However, prolonged high cortisol levels signal the body to diversify its fueling sources—including breaking down muscle for energy. When cortisol and stress levels are elevated, performance and recovery can decline. [4]

Post-marathon cortisol levels increase proportionally to testosterone’s decrease. High cortisol combined with low testosterone is characteristic of inadequate recovery. In fact, changes in cortisol levels typically correspond to similar changes in testosterone post-marathon. [5]

» Discover how to manage high cortisol levels

4. Creatine kinase

Creatine kinase is an enzyme primarily stored in muscle tissue. During intense training, it leaks into the bloodstream, rising about 12-48 hours post-workout. [6] Moderate levels of creatine kinase in the blood are normal. However, high creatine kinase levels can indicate muscle damage. So, creatine kinase levels can show how much your muscles are over-exerted.

Studies show that creatine kinase levels peak about 24 hours after intense exercise. And though creatine kinase levels tend to decrease after that 24-hour mark, they can remain elevated for six days post-race. [7] Interestingly, the rate of creatine kinase recovery is an indicator of how the body handled its training. Creatine kinase levels tend to recover faster after a marathon in trained athletes but can recover more slowly in overtrained individuals.

» Take control with regular biomarker testing



Biomarkers to optimize before race day

Other biomarkers, when left unoptimized, impact marathon performance. For example, ferritin (the storage form of iron), vitamin D, and vitamin B12 are three biomarkers to be proactive about prior to race day.

» Read more about how these three biomarkers impact athletic performance

What to do within 24 hours of a marathon to properly recover

Running a marathon is a huge physical feat, and it can cause significant immediate damage to the body. Proper rest and recovery are essential to ensuring longevity in the sport—and the first 24 to 48 hours after a race are the most critical.

» Explore clear warning signals of overtraining

Hydrate and replace electrolytes

Your absolute first priority after crossing that finish line should be to hydrate and get some electrolytes. “You should be getting 24 ounces of fluid per pound of weight lost,” says Stevie, “and there’s usually about 1 gram of sodium in every liter of sweat.” So, say you lose 2 pounds of body weight after a marathon, you would need to consume about 47 ounces of fluid (about 1.4 L) and about 1.4 grams of sodium.

Don’t feel the need to chug this all at once, but rehydrating with fluids and electrolytes is an immediate priority post-marathon. [7]

» Maintain peak performance with hydration, sodium, and potassium

Eat a balanced recovery meal

What you eat is just as crucial as what you drink. And electrolytes like sodium can also come from food. The ideal post-marathon meal contains a balance of carbohydrates, protein, fat, and micronutrients. [7]

You need protein to prevent excess muscle breakdown and carbohydrates to replenish energy stores. An ideal ratio of these two macronutrients is 3 grams of carbohydrates to every gram of protein consumed. [8, 9]

» Wiped out? Try these foods to help you recover

If you can’t eat a full meal within an hour after the race, opt for a snack first to keep you going. 

» Learn how tailored dietary plans can optimize your health and well-being

Keep moving, but slowly

Runners and running coaches also recommend light, easy movement post-marathon. Jonathan says he likes to walk for 30 minutes after a race as a form of active recovery. Stevie adds, “This will allow your heart rate time to slowly lower and keep blood flow strong to the exhausted muscles—helping clear lactic acid and initiating the recovery process." [9]

» Understand your heart rate variability and how it impacts your overall health

What not to do post marathon—habits that prolong recovery

Certain choices you make post-marathon may actually hinder recovery and delay the healing process.

Don’t drink too much alcohol

Finishing a marathon is a feat to celebrate! Drinking alcoholic beverages is frequently a part of those festivities. “Alcohol can negatively affect muscle protein synthesis, which interferes with repairing the damaged muscles from the marathon,” says Stevie. But the choice to consume alcohol or not post-marathon is highly personal. 

Jonathan also says he often sees runners switch to beer too fast after a race without drinking enough water. And beer and other alcoholic beverages don’t count towards those post-marathon rehydration goals. Alcohol acts as a diuretic, further ridding the body of salt and water. When already dehydrated from sweat loss post-marathon, alcohol intake can make matters worse. [10] So, be sure to replenish with fluid and electrolytes before having a celebratory beverage. 

» Find out how alcohol affects your athletic performance

Don’t restrict or limit food intake 

In the hours and days following a marathon, you should aim to eat consistent meals and snacks throughout the day to get enough carbohydrates, fat, protein, and color. Evidence suggests that beneficial plant compounds called polyphenols (like those in green tea) may help mitigate exercise-induced muscle damage and oxidative stress. [11]

» Learn why you should consume a colorful variety of fruits and vegetables for a balanced diet

When counseling her clients, Stevie often encourages them to lean into their hunger cues. “It’s normal for appetite to be suppressed for a day or two after a marathon. So when the hunger hits, it’s important to listen to your body—if a burger sounds good, have a burger! Just don’t neglect nutrient-dense foods." [7] 

» Learn more about how underfueling impacts performance—and how to prevent it

Don’t do too much too soon

Take some time off from intense exercise after a marathon. Your body needs time to rest and recover.

Marathons can throw biomarkers like CK, testosterone, cortisol, and hsCRP completely out of whack, and the best way to get them back to optimized is through resting your stressed body—not by piling on more pressure.

Lower-intensity activities like walking, yoga, or stretching offer the benefits of movement while allowing those biomarkers to recalibrate. After proper rest and recovery, you can pick up your training volume again. 

» Listen to your body—know when to rest and skip your workout for better health

Should you run the day after a marathon? 

The short answer is probably not. And this is a great example of doing too much too soon.

“Running the day after completing a marathon is not recommended. How long that rest period lasts should be based on a number of factors. This includes an athlete's training status, goals, and mental and physical health. For the most part, I’d recommend taking at least a whole week off from running (if not more),” says Stevie. 

Some people may be ready to run again within a week, whereas others want to take more time off. And some runners may choose to run races back-to-back or within the same week. It’s best to talk with a running coach to determine your ideal race and training schedule. But running too hard too soon after a marathon may increase the risk of injuries. [12]



Why can’t you sleep after a marathon?

“Sleep can be challenging after a hard physical effort for a number of reasons. A hormonal response to exercise, including cortisol and norepinephrine (which makes your heart beat faster), dehydration, elevated core body temperature, and high caffeine intake during races can all negatively impact sleep,” says Stevie.

High heart rates keep you alert, which is not ideal for sleep. Body temperature begins to drop around bedtime, so a high internal temperature can delay the signal that it’s time to wind down and go to sleep.

» Discover how magnesium can improve your sleep, memory, and mood

A post-race high is also common among runners. This high can be emotionally and physically driven. You’re proud of yourself for finishing a marathon, and your stress hormones cortisol, norepinephrine, and adrenaline are likely still elevated. A 2020 study shows that norepinephrine and adrenaline return to near-normal by a week after a marathon. [13]

» Gain insight into the importance of sleep for athletes and the consequences of sleep deprivation on performance

When should you contact a doctor or other health professional?

Different bodies recover at different speeds. However, “after proper rest, the biomarkers related to muscle health, immune health, and stress that spiked because of the marathon should start to drop back to normal levels,” says Stevie. “If these biomarkers remain extremely elevated a few weeks post-race, I’d recommend evaluating your rest and recovery and contacting a professional.” 

A blood test is needed to measure these biomarkers. If you're running consecutive races, consider getting a blood test between them. The results will provide an objective view of your body's recovery progress and reveal whether you have mended sufficiently for your next race.

» Learn all about blood biomarkers and how to interpret your blood test results

How can InsideTracker help with your post-race recovery?

InsideTracker can measure your blood biomarkers and show you what you need to do to improve them. Their most comprehensive package—the Ultimate Plan—can analyze:

• hsCRP
• Testosterone (men and women)
• Cortisol
• CK
• Ferritin
• Vitamin D
• Vitamin B12

After getting your results, you can choose a specific goal, such as enhancing endurance. Then, based on your selection, InsideTracker will give you personalized food, supplements, and lifestyle recommendations to support your progress. And if you have an Apple Watch, Garmin smartwatch, or Fitbit, the devices can sync with the InsideTracker app and pull data on your heart rate and sleep.

Get ready to chase down your next personal best

Running a marathon is an incredible accomplishment that pushes your body to its limits. But with the right combination of rest, nutrition, and personalized insights, you can bounce back stronger and ready for your next race.

Remember, every runner's journey is unique. So, listen to your body, celebrate your achievements, and embrace the process of continuous improvement.

» Unlock your full potential and enjoy a lifetime of running success

References:

1. C. C. Kaufmann et al., “Effect of marathon and ultra‐marathon on inflammation and iron homeostasis,” Scandinavian Journal of Medicine & Science in Sports, vol. 31, no. 3, pp. 542–552, Nov. 2020, doi: 10.1111/sms.13869. Available: https://pubmed.ncbi.nlm.nih.gov/33140866/
2. M. D. Bernat-Adell et al., “Recovery of inflammation, cardiac, and muscle damage biomarkers after running a marathon,” Journal of Strength and Conditioning Research, vol. 35, no. 3, pp. 626–632, Mar. 2021, doi: 10.1519/jsc.0000000000003167. Available: https://pubmed.ncbi.nlm.nih.gov/31045685/
3. H. Mairbäurl, “Red blood cells in sports: effects of exercise and training on oxygen supply by red blood cells,” Frontiers in Physiology, vol. 4, Jan. 2013, doi: 10.3389/fphys.2013.00332. Available: https://pubmed.ncbi.nlm.nih.gov/24273518/
4. M. Marinelli, G. S. Roi, M. Giacometti, P. Bonini, and G. Banfi, “Cortisol, Testosterone, and Free Testosterone in Athletes Performing a Marathon at 4,000 m Altitude,” Hormone Research, vol. 41, no. 5–6, pp. 225–229, Jan. 1994, doi: 10.1159/000183929. Available: https://pubmed.ncbi.nlm.nih.gov/7959625/
5. H. Keizer, G. M. Janssen, P. Menheere, and G. Kranenburg, “Changes in basal plasma testosterone, cortisol, and dehydroepiandrosterone sulfate in previously untrained males and females Preparing for a marathon,” International Journal of Sports Medicine, vol. 10, no. S 3, pp. S139–S145, Oct. 1989, doi: 10.1055/s-2007-1024962. Available: https://pubmed.ncbi.nlm.nih.gov/2532181/
6. P. Brancaccio, N. Maffulli, and F. M. Limongelli, “Creatine kinase monitoring in sport medicine,” British Medical Bulletin, vol. 81–82, no. 1, pp. 209–230, Feb. 2007, doi: 10.1093/bmb/ldm014. Available: https://pubmed.ncbi.nlm.nih.gov/17569697/
7. N. B. Tiller et al., “International Society of Sports Nutrition Position Stand: nutritional considerations for single-stage ultra-marathon training and racing,” Journal of the International Society of Sports Nutrition, vol. 16, no. 1, Jan. 2019, doi: 10.1186/s12970-019-0312-9. Available: https://pubmed.ncbi.nlm.nih.gov/31699159/
8. K. M. Zawadzki, B. B. Yaspelkis, and J. L. Ivy, “Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise,” Journal of Applied Physiology, vol. 72, no. 5, pp. 1854–1859, May 1992, doi: 10.1152/jappl.1992.72.5.1854. Available: https://pubmed.ncbi.nlm.nih.gov/1601794/
9. P. Menzies, C. Menzies, L. McIntyre, P. Paterson, J. Wilson, and O. J. Kemi, “Blood lactate clearance during active recovery after an intense running bout depends on the intensity of the active recovery,” Journal of Sports Sciences, vol. 28, no. 9, pp. 975–982, Jul. 2010, doi: 10.1080/02640414.2010.481721. Available: https://pubmed.ncbi.nlm.nih.gov/20544484/
10. L. D. Vella and D. Cameron-Smith, “Alcohol, athletic performance and recovery,” Nutrients, vol. 2, no. 8, pp. 781–789, Jul. 2010, doi: 10.3390/nu2080781. Available: https://pubmed.ncbi.nlm.nih.gov/22254055/
11. M. Malaguti, C. Angeloni, and S. Hrelia, “Polyphenols in exercise performance and Prevention of Exercise-Induced muscle damage,” Oxidative Medicine and Cellular Longevity, vol. 2013, pp. 1–9, Jan. 2013, doi: 10.1155/2013/825928. Available: https://pubmed.ncbi.nlm.nih.gov/23983900/
12. M. Fredericson and A. K. Misra, “Epidemiology and Aetiology of marathon Running Injuries,” Sports Medicine, vol. 37, no. 4, pp. 437–439, Jan. 2007, doi: 10.2165/00007256-200737040-00043. Available: https://pubmed.ncbi.nlm.nih.gov/17465629/
13. J. Chmura et al., “The Effects of a Marathon Effort on Psychomotor Performance and Catecholamine Concentration in Runners over 50 Years of Age,” Applied Sciences, vol. 10, no. 6, p. 2067, Mar. 2020, doi: 10.3390/app10062067. Available: https://www.mdpi.com/2076-3417/10/6/2067