Physiology and Pathophysiology of Marathon Running: A narrative Review

Abstract

Background: Marathon training and running have many beneficial effects on human health and physical fitness; however, they also pose risks. To date, no comprehensive review regarding both the benefits and risks of marathon running on different organ systems has been published.

Main body: The aim of this review was to provide a comprehensive review of the benefits and risks of marathon training and racing on different organ systems. A predefined search strategy including keywords (e.g., marathon, cardiovascular system, etc.) and free text search was used. Articles covering running regardless of sex, age, performance level, and event type (e.g., road races, mountain marathons) were considered, whereas articles examining only cycling, triathlon, stress-tests or other sports were excluded. In total, we found 1021 articles in PubMed, Scopus, and Google Scholar, of which 329 studies were included in this review. Overall, marathon training offers several benefits for different organ systems and reduces all-cause mortality. As such, it improves cardiovascular risk factors, leads to favorable cardiac adaptations, enhances lung function, and improves quality of life in chronic kidney disease patients. It also enhances gastrointestinal mobility and reduces the risk of specific tumors such as colorectal cancer and hepatocellular carcinoma. Marathon training enhances bone health and skeletal muscle metabolism. It further positively affects hematopoiesis and cytotoxic abilities of natural killer cells, and may act neuroprotective on a long-term basis. After a marathon, changes in biomarkers suggesting pathological events in certain organ systems such as cardiovascular, renal, gastrointestinal, liver, hematological, immune, musculoskeletal, central nervous, and endocrine systems can often be observed. Mostly, these changes are limited to 1-3 days post-race and usually normalize within a week. Moreover, marathon running poses the risk of serious adverse events such as sudden cardiac death or acute liver failure. Concerning lung function, a decrease after a marathon race was observed. Acute kidney injury, as well as electrolyte imbalances, are relatively common amongst marathon finishers. Many runners complain of gastrointestinal symptoms during or after long-distance running. Many runners suffer from running-related musculoskeletal injuries often impairing performance. A marathon is often accompanied by an acute inflammatory response with transient immunosuppression, making runners susceptible to infections. Also, hormonal alterations such as increased cortisol levels or decreased testosterone levels immediately after a race are observed. Disturbances in sleep patterns are commonly found in marathon runners leading up to or directly after the race.

Conclusion: All in all, marathon training is generally safe for human health and individual organ systems. Considering the high popularity of marathon running, these findings supply athletes, coaches, sports scientists, and sports medicine practitioners with practical applications. Further large-scale studies examining long-term effects on the cardiovascular, renal, and other system are needed.

Keywords: Athletic injury; Endurance training; Exercise overtraining; Sex differences; sports performance.

Fig. 1

Mean changes in CK-MB, hs-cTnT, and NT-proBNP in studies investigating cardiac biomarkers before and after a marathon [, , , , –, , , , , , , –246, 252, 252, 253, 311, 311, 363]. CK-MB, creatine kinase myocardial band; hs-TnT, high-sensitive cardiac troponin T; NT-proBNP, N-terminal prohormone of brain natriuretic peptide

Fig. 2

Mean changes in serum creatinine, cystatin C, and blood urea nitrogen in studies investigating renal biomarkers before and after a marathon [, –, , –, , , , , , –158, 195, 196, 199, 243, 244, 254]

Fig. 3

Mean changes in serum sodium, potassium, calcium, magnesium, and phosphorus in studies investigating electrolytes before and after a marathon [42, 45, 47, 59, 89, 106, 156, 243, 244, 255, 271, 271, 314]

Fig. 4

Mean changes in ALT, AST, total, direct, and indirect bilirubin in studies investigating hepatic and cholestasis biomarkers before and after a marathon [45, 59, 84, 106, 195, 196, 199, 246, 254, 316]. ALT, alanine transaminase; AST, aspartate transaminase

Fig. 5

Mean changes in hemoglobin, hematocrit, and LDH in studies investigating hematological biomarkers before and after a marathon [, , , , , –, , –, , , , , , , , , , –273, 286, 308, 311, 314, 316, 326, 333]. LDH, lactate dehydrogenase

Fig. 6

Mean CK and myoglobin changes in studies investigating biomarkers of muscle damage before and after a marathon [, , , , , , , , , , , , , , , , –, –255, 260, 311, 363]. CK, creatine kinase

Fig. 7

Mean changes in erythrocytes, leukocytes, platelets, and leukocyte subtypes in studies investigating total blood count before and after a marathon [, , , , , , , , , –, , –274, 286, 295, 297, 306, 308, 311, 326, 339]

Fig. 8

Mean changes in ferritin, transferrin, transferrin saturation, and serum iron in studies investigating the iron status before and after a marathon [16, 59, 246, 254]

Fig. 9

Mean changes in D-dimer and fibrinogen in studies investigating the prothrombotic state before and after a marathon [89, 244, 245, 273, 284, 287, 290, 292, 358]

Fig. 10

Mean changes in CRP, TNFα, IL-6, and IL-10 in studies investigating pro- and anti-inflammatory biomarkers before and after a marathon [29, 64, 86, 87, 90, 123, 133, 178, 223, 225, 226, 281, 282, 294, 304]. CRP, C-reactive protein; IL, interleukin; TNFα, tumor necrosis factor alpha

Fig. 11

Behavior of immune function after high-intensity endurance exercise such as marathons (adapted from Åkerström and Pedersen [318], with permission)

Fig. 12

Association between exercise amount and intensity and risk of upper respiratory tract infections (adapted from Nieman [301], with permission)

Fig. 13

Mean changes in glucose, LDL cholesterol, HDL cholesterol, triglycerides, and serum cortisol in studies investigating endocrine biomarkers before and after a marathon [, , , , , , , –, , –314, 342, 343]. HDL, high-density lipoprotein; LDL, low-density lipoprotein