Collagen genes and
exercise-associated muscle cramping

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
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?

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


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