Sports Medicine Research: In the Lab & In the Field: Are Your Parents Cramping Your Style? (Sports Med Res)


Monday, September 17, 2012

Are Your Parents Cramping Your Style?

Collagen genes and exercise-associated muscle cramping

O’Connell K., Posthumus M., Schwellnus MP., Collins M. Clinical Journal of Sports Medicine. 2012; ahead of print

Previous research has shown that variants, like single nucleotide polymorphisms (SNPs), within collagen genes (e.g., COL5A1, COL3A1, COL6A1, and COL12A1) can influence the structure and function of different collagen fibers. Furthermore, altered collagen fibers may be a predisposing factor to exercise-associated muscle cramping, however, research has yet to examine if genetic variants in these collagen genes are associated with a history of exercise-associated muscle cramping among runners. Therefore, the purpose of this study was to determine if 4 SNPs within 4 different collagen genes were associated with a history of exercise-associated muscle cramping in ironman triathletes and ultra marathoners. Two hundred sixty-eight athletes were recruited from either the 2006 and 2007 African Ironman triathlons (n = 211) or the 2009 and 2011 Two Oceans ultra-marathon (n = 57). One hundred eighteen participants reported a history of exercise-associated muscle cramping (defined as a painful spasm occurring during a competition or within 6 hours after a competition) within the past year. One hundred fifty athletes reported that they never had an exercise-associated muscle cramp in their lifetime. DNA was extracted from the participants’ blood samples. The investigators, who were blinded to the athletes’ phenotypes (history of exercise-associated muscle cramping or no history of muscle cramping), obtained the genotypes for COL5A1 rs 12722, COL3A1 rs 1800255, COL6A1 rs 35796750, and COL12A1 rs 970547 among 264, 228, 209, 225 participants, respectively. There were no differences found in triathlon training distance between muscle-cramping and non-muscle cramping athletes, and no training data was collected for marathoners. The authors found that a genetic variant in COL5A1 (COL5A1 rs 12722) along with participant weight, height, and self-reported history of tendon or ligament injury were associated with an increased risk of history of exercise-associated muscle cramping (CC vs TC or TT alleles; an alternate form of a gene at a specific location). There were no associations among the three other SNPs and a history of muscle cramping.

Genetic variants located within the collagen genes can alter the amino acid sequence and/or change the amount of protein produced. These changes can alter the overall structure and function of the muscles. Within this study, researchers established that a genetic variant in COL5A1 (COL5A1 rs 12722); which was previously associated with reduced tensile strength of collagen fibers, increased muscle stiffness, and decreased muscular endurance; may also be associated with exercise-associated muscle cramping. Specifically, those carrying the T allele (TT or TC genotype) were more likely to have a history of exercise-associated muscle cramping compared to those with the CC genotype. These results suggest that changes to type V collagen containing tissue may modify the risk of a history of exercise-associated muscle cramping. Prospective studies with larger cohorts will be necessary to assess a cause-effect relationship. Do you believe screening for these SNPs may help with preventative measures to decrease muscle cramping in ultra endurance athletes?

Written by: Jane McDevitt MS, ATC, CSCS
Reviewed by: Jeffrey Driban

Related Posts:
O'Connell K, Posthumus M, Schwellnus MP, & Collins M (2012). Collagen Genes and Exercise-Associated Muscle Cramping. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine PMID: 22894972


Nicole Cattano said...

Interesting post Jane! Is the implications of this limited to ultra-marathoners, or is it possible that this could be implicated in our more traditional sports as well? Also, if we pre-screened and found this SNP, what could we do differently from a prevention standpoint?

Jane McDevitt said...


Great question! I believe this SNP would effect any endurance athlete. The authors probably used ultra marathoners to ensure they would have enough crampers and non crampers in each group, especially since the rare allele (typically the disease causing allele) frequency is low. They used ultra marathoners and triathletes because they have a lifetime reported prevalence of 67% of exercised associated muscle cramping as opposed to the normal physical athletes have only a lifetime reported prevalence of 26%.

I dont know a whole lot about exercise associated muscle cramping. Several hypotheses of how exercise associated muscle cramping occurs is due to electrolyte depletion, dehydration, and neuromuscular control. Athletes with the COL5A1 rs 12722 SNP may need to take extra care with their nutrition and hydration. You could also try neuromuscular control programs to help prevent this type of injury.

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