What does a world record ultramarathon do to your biomarkers?

Which biomarkers did we track?

We set Sophie up with multiple testing kits to assess her Vitamin D status, cholesterol levels, B vitamins, inflammatory markers and liver biochemistry.

The first kit was used on the morning of her world record attempt, before Sophie started running. The remaining tests were taken immediately after and in the weeks and months that followed.

What did we see in Sophie’s results?

As you can imagine, there are a lot of biological processes that are affected when someone undertakes such an extreme amount of endurance exercise. Here are a few key markers that saw a dramatic effect.

Inflammation

C-reactive protein (hs-CRP) is an inflammatory marker that can rise significantly, most commonly in response to acute infective illness or inflammation (such as autoimmune disease). It can also rise due to extreme physical stress and muscle damage, as seen in Sophie's case. Forty-eight hours on a treadmill can produce a high level of muscle breakdown and oxidative stress, leading to an acute inflammatory response in the body.

Sophie’s hs-CRP the morning after her world record rose to an incredible 154* mg/L, noting that the normal range is below 3 mg/L. Her levels had dropped to 33.7 mg/L by the fourth day, but remained elevated until a full two months afterwards. Such a prolonged elevation in the blood just shows you how long her body needed to fully repair itself after such an effort. 

*Although very uncommon, we have seen other Thriva users with hs-CRP levels this high. Results at this level would be acknowledged by the reporting doctor and often require the user to urgently follow up with their GP in person, as there are many potentially serious causes of raised hs-CRP, such as acute infection or underlying illness. This is why context is very important, and Sophie’s results were interpreted in the context of extreme exercise. 

Kidney Function

Creatinine is a by-product of muscle metabolism and is usually filtered by the kidneys. At Thriva, we use creatinine to estimate your Glomerular Filtration Rate (eGFR), a marker of kidney function. Higher creatinine levels can indicate an inability to effectively clear the body of creatinine. Additionally, if Sophie was suffering from dehydration post-run this can further drive up creatinine levels.

Running 230 miles led to a 10% increase in creatinine in Sophie's blood, which her body was able to normalise within the following days. It’s also worth mentioning that her own personal baseline is much higher than the average female Thriva user, which is 72.7 μmol/L.

Interestingly, a 2022 study on ultramarathoners found that females didn’t experience as significant a post-exercise rise in creatinine as males. This is likely a result of the relative differences in total muscle mass. We can see a similar effect when looking at Thriva user data, where males who undertake more than 300 minutes of resistance training per week have average creatinine levels 11.1% above non-exercisers, while for females that increase is only 5.9%.

Ferritin

Ferritin is an iron storage protein, and its levels can rise sharply in response to inflammation or physical stress. These rises don’t necessarily reflect an increase in iron stores, but rather a short-term response triggered by extensive muscle breakdown and tissue repair.

Sophie saw a near threefold increase in her Ferritin levels, from 86 mcg/L up to 243 mcg/L. Despite her post-race result being classified as “high”, her levels had normalised by day 8. This indicates that her changes were likely a reaction to exercise and not a chronic issue.

This temporary spike in Ferritin isn’t unique to ultra runners and may also occur in the general population after moderate exercise. For this reason, doctors may recommend a follow-up test to determine whether “high” results are reflective of a true issue or simply a short-term response to exercise.

Liver markers

Alanine aminotransferase (ALT) is an enzyme found primarily in liver cells, but it is also present in skeletal muscle. During long-distance running, muscle breakdown can release significant amounts of ALT into the bloodstream, leading to elevated levels that are not related to any issue with the liver itself.

In Sophie’s case, ALT spiked from an optimal 22 IU/L to a peak of 254 IU/L post-run. The body’s repair processes take time, especially from such a highly demanding event, and one week later her levels were still up at 82 IU/L - four times her baseline.

As with other markers, it’s important for doctors to be able to differentiate between results that are elevated due to exercise or because of an underlying health condition. This is where markers like Gamma-glutamyl transferase (GGT) come into play. Sophie’s GGT remained optimal (12-21 IU/L) across all six of her blood tests, evidence that her ALT rise was linked to muscle stress and not liver dysfunction.

Cholesterol

There were changes to Sophie’s cholesterol levels, but perhaps not what you might expect. During prolonged physical activity, the body increasingly relies on fat-based energy sources, including lipoproteins, which make up the different components of cholesterol.

Sophie’s non-HDL cholesterol levels dropped from 2.8 mmol/L to 1.9 mmol/L, an indication that her fat reserves were utilised to help fuel her run. They were still lower four days later (2.2 mmol/L) before normalising on day 8. This is consistent with what research has observed in the post-race lipid levels of marathon runners.

What does this mean for the rest of us?

Sophie’s record-breaking effort gives us a unique look into how the body responds to extreme physical stress. However, even if you're not running 230 miles on a treadmill, many of the same principles still apply. Intense or prolonged exercise can temporarily alter key blood markers, especially those related to inflammation, liver function and iron status.

These fluctuations are part of the body’s adaptive response to exercise and are important for athletes of all levels to understand when taking their test. Knowing how your body responds to exercise and when it returns to baseline can help you better time your test and get the most accurate interpretation of your biomarkers at rest. 

Hopefully this article has helped to shine a light on the acute effects of exercise and its wide-ranging influence in the body.