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Muscle Cramping in the Marathon: Dehydration and Electrolyte Depletion vs. Muscle Damage

Journal of Strength and Conditioning Research: June 2022 - Volume 36 - Issue 6 - p 1629-1635 doi: 10.1519/JSC.0000000000003713


To compare dehydration variables, serum electrolytes, and muscle damage serum markers between runners who suffered exercise-associated muscle cramps (EAMC) and runners who did not suffer EAMC in a road marathon. Also analyzed was race pacing and training background.


Nighty-eight marathoners took part in the study. Subjects were subjected to a cardiopulmonary exercise test. Before and after the race, blood and urine samples were collected and body mass (BM) was measured. Immediately after the race EAMC were diagnosed. Eighty-eight runners finished the marathon, and 20 of them developed EAMC (24%) during or immediately after the race.


Body mass change, post-race urine specific gravity, and serum sodium and potassium concentrations were not different between crampers and noncrampers.

Conversely, runners who suffered EAMC exhibited significantly greater post-race levels of:

  -  Creatine kinase (464.17 ± 220.47 vs. 383.04 ± 253.41 UI/L).

  -  Lactate dehydrogenase (LDH) (362.27 ± 72.10 vs. 307.87 ± 52.42 UI/L).

Twenty-four hours post-race the values of both biomarkers were higher among crampers:

  -  CK: 2,438.59 ± 2,625.24 vs. 1,166.66 ± 910.71 UI/L.

  -  LDH: 277.05 ± 89.74 vs. 227.07 ± 37.15 UI/L.

The difference in the percentage of runners who included strength conditioning in their race training approached statistical significance (EAMC: 25%, non-EAMC: 47.6%).

Eventually, relative speed between crampers and noncrampers only differed from the 25th km onward. Therefore, runners who suffered EAMC did not exhibit a greater degree of dehydration and electrolyte depletion after the marathon but displayed significantly higher concentrations of muscle damage biomarkers.


Ultimately, muscle cramping and the inability to function at an optimal level is caused by many factors. It is normally thought that muscle cramps are caused solely by dehydration and electrolyte depletion. However, cramping can also be caused by muscle damage in extended events (i.e., marathon) as indicated by the presence of higher levels of lactate dehydrogenase (LDH) and creatine kinase (CK), two enzymes that catalyze energy production.

Muscle damage can be avoided or at least minimized if prior strength training is incorporated as a part of an extended event training program.

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