Exercise-associated Muscle Cramps in Runners : A Review

revalence of Exercise-associated muscle cramp (EAMC) has been reported in different studies and groups of athletes [1-5]. One of these groups is runners [6, 7]. Due to the fact that a lot of muscles are used during running and the amount of energy consumed in these runners is high, and considering that no review study was not found that addressed the causes of EAMC in runners, this review study aims to investigate EAMC in runners to determine the cause and general nature of EAMC in this sport to provide P more complete and better information for interventions and future studies on EAMC in runners. As a result, it can help prevent, treat and reduce its occurrence.

Hanson et al. [39] Potential nutrition contributions to exercise-associated muscle cramping in four recreational half-marathoners: A case series Case series Half-marathon The observed case of EAMC does not appear to be entirely inconsistent with the traditional dehydration/ electrolyte loss theory.

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Fredericson et al. [40] Disabling foot cramping in a runner secondary to paramyotonia congenita: A case report Case report Endurance running The runner had cramping in left foot. His symptoms developed insidiously after about 20 minutes of exercise. The more he continued to run, the more the symptoms were aggravated. This symptom was easily provoked when he was exposed to cold temperature.

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Caselli et al. [41] Lower extremity injuries at the New York City marathon

Cross-sectional Marathon
Their results indicated that muscle cramps was one of the most common injuries occurring in marathon runners. An inverse relationship was observed between the number of miles trained per week and the number of injuries

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Ferreira et al. [42] Hydration practices of runners during training vs competition Cross-sectional -A significant difference was observed for reported hydration practices between training and competitions. 41 % of runners in competitions and 54% in training had inadequate hydration habits. Runners were not able to transfer their knowledge about proper hydration during both training and competition practices.
Hawes et al. [43] Exertional heat illness in half marathon runners: experiences of the Great North Run Cross-sectional Half marathon As the exercise intensity increased and the body temperature rose above 41 degrees, the athletes were more likely to fall. Under these conditions, during cooling and recovery, muscle cramps occurred in runners.

Cross-sectional Marathon
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.

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Hoffman et al. [45] Muscle cramping during a 161km ultramarathon: Comparison of characteristics of those with and without cramping Observational Ultramarathon Muscle cramping is most common in those with a prior history of cramping and greater muscle damage during an ultramarathon, suggesting an association with relative muscular demand. Impaired fluid and sodium balance did not appear to be an etiology of muscle cramping during an ultramarathon.

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Schwellnus et al. [46] Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exerciseassociated muscle cramping: A prospective cohort study in 210 Ironman triathletes Prospective cohort Triathletes The results from this study add to the evidence that dehydration and altered serum electrolyte balance are not causes for EAMC. Rather, endurance runners competing at a fast pace, which suggests that they exercise at a high intensity, are at risk for EAMC.

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Schwabe et al. [47] Medical complications and deaths in 21 and 56 km road race runners: A 4-year prospective study in 65 865 runners-SAFER study I

Prospective cohort Marathon
The incidence of medical complications was higher in 56 km runners but sudden cardiac deaths only occurred in 21 km runners.

Cross-sectional
Endurance running Abdominal cramping was directly related to dietary restrictions. The prevalence of these cramping was higher in younger athletes, especially females, which may explain their propensity to avoid foods. There are no clinically significant alterations in serum electrolyte concentrations and there is no alteration in hydration status in runners with EAMC participating in an ultra-distance race
Cross-sectional Ultramarathon and marathon Moderate, mostly negative, correlations with nutrient intake were seen for abdominal cramping. During a competition day, a large variation was found in nutrient intake; this may be related to a high incidence of abdominal cramping 7/11 or ultrarunning or athletes or athletic performance, exercise or endurance exercise, water-electrolyte imbalance, electrolytes or dehydration or sports nutrition or hydration. After finding articles, first their title and abstracts and then their contents were read. If they met the inclusion criteria, they would be used in the review. Inclusion criteria were: Being published in Persian or English, studies on EAMC in runners, and availability of fulltexts.

Results
The search in online databases yielded 326 articles. By reviewing their reference sections, 5 more articles were yielded. After removing duplicates, 241 were identified for review. After reviewing their titles and abstracts, 202 were deleted and 39 remained for reading their fulltexts. Finally, 15 eligible articles were selected and their results were reported (Table 1).

Discussion and Conclusion
The purpose of this study was to investigate EAMC in runners. Studies have reported a variety of information on EAMC in runners. Studies showed that the causes of EAMC are: dehydration and electrolyte deficiency, cold, prolonged training or competition, increased body temperature during training or competition, history of muscle injuries and cramps in the past, increased intensity of training in a short time, and dietary restrictions. Therefore, in order to reduce the occurrence EAMC in runners, it is necessary to consider these factors and study them in detail.

Compliance with ethical guidelines
There were no ethical considerations to be considered in this research.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or profit-non sectors.

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.