CLASSIFICATION OF EXERCISE-ASSOCIATED MUSCLE CRAMPS IN IRONMAN-DISTANCE TRIATHLETES OVER THREE DECADES

Abstract

Exercise-associated muscle cramps (EAMC) is a common condition in ultra-endurance athletic events. Despite its high incidence, the etiology and risk factors are not fully understood. PURPOSE: The purpose of this study was to explore trends in Ironman-distance triathletes, that presented to the medical tent during competition with muscle cramping as well as those who returned with subsequent cramping after initial treatment. METHODS: Medical records (n=10,553) from the 1989-2019 Ironman World Championship (Kona, HI) were reviewed. Independent samples t-tests were run and odds ratios were calculated to compare athletes with cramping (n=2,859) to those without (n=7,670). The same analyses were used to compare those who returned to the tent with muscle cramps (n=377) to those who had muscle cramps and did not subsequently return with muscle cramps (n=2,248). RESULTS: Triathletes who presented with muscle cramps were more likely to have a history of previously reporting to the medical tent with muscle cramps within the same race compared to those presenting without muscle cramps (OR 2.40; 95% CI = 1.91-3.03). Triathletes who presented with muscle cramps had slightly higher serum sodium (140 +/- 7 vs. 139 +/- 7 mEq/L, p = .007) and potassium (4.3 +/- 0.7 vs. 4.2 +/- 0.6 mEq/L, p < .001) concentrations than those without muscle cramps. Dehydration was more common in triathletes with muscle cramps (OR 1.63; 95% CI = 1.49-1.78) compared to those without. Male triathletes were much more likely to present with muscle cramps than female triathletes (29 vs. 22%, p < .001). For those returning to the medical tent with muscle cramps, faster race completion time was associated with increased risk of returning with muscle cramps (11.0 +/- 1.9 vs. 11.4 +/- 1.8 hours, p < .001). CONCLUSIONS: Our findings from nearly 30 years of elite ultra-endurance data indicate that muscle cramps are likely to be a reoccurring issue throughout the race and are more common among males. We confirm that electrolyte abnormalities are not associated with muscle cramps during ultra-endurance competition. Our finding that dehydration is associated with muscle cramps is somewhat contradictory to current literature.