1 Medicine & Science in Sports & Exercise: November 1997 - Volume 29 - Issue 11 - pp 1444-1447 Muscle-specific creatine kinase gene polymorphisms in elite endurance athletes and sedentary controls RIVERA, MIGUEL A.; DIONNE, FRANCE T.; WOLFARTH, BERND; CHAGNON, MONIQUE; SIMONEAU, JEAN-AIMÉ; PÉRUSSE, LOUIS; BOULAY, MARCEL R.; GAGNON, JACQUES; SONG, THOMAS M. K.; KEUL, JOSEPH; BOUCHARD, CLAUDE Physical Activity Sciences Laboratory, Laval University, Québec, G1K 7P4, CANADA; Department of Physical Medicine, Rehabilitation and Sports Medicine, University of Puerto Rico Medical School, San Juan, PUERTO RICO, 00936; Department of Rehabilitation and Preventive Sports Medicine, Freiburg University, Freiburg, GERMANY; and Human Performance Laboratory, Lakehead University, Thunder Bay, Ontario, P7B 5E1, CANADA Abstract The purpose of this study was to investigate the association between elite endurance athlete (EEA) status and two restriction fragment length polymorphisms (RFLPs) at the muscle-specific creatine kinase (CKMM) gene locus. Genomic DNA was extracted from white blood cells or lymphoblastoid cell lines of 124 unrelated Caucasian male EEA (˙VO 2max >73 mL·kg -1 ·min -1 ) and 115 unrelated Caucasian sedentary male controls (SCON). The genetic polymorphism at the CKMM locus was detected by the polymerase chain reaction and DNA digestion with theNcoI and TaqI restriction endonucleases. The allelic frequencies for the NcoI and TaqI RFLPs were not different(P > 0.05) between EEA and SCON subjects. The three expected genotypes for CKMM-NcoI (1170/1170 bp, 1170/985 + 185 bp, and 985 + 185/985 + 185 bp) and CKMM- TaqI (1170/1170 bp, 1170/1020 + 150 bp, and 1020 + 50/1020 + 150 bp) were observed in the EEA and SCON groups. These genotype frequencies were in Hardy-Weinberg equilibrium, but they were not significantly (P > 0.05) different between the EEA and SCON. A strong (P < 0.001) linkage disequilibrium was detected among theNcoI and TaqI RFLPs in both EEA and SCON. These findings indicate that the skeletal muscle CK-NcoI and CK-TaqI gene polymorphisms are not associated with the elite endurance athlete status. It is widely accepted that the biological characteristics required to achieve an elite endurance performance are significantly determined by genetic factors. Since several determinant factors contribute to success in endurance performance, it is obvious that several genes are involved. One line of research we are pursuing has to do with the possible contribution of DNA sequence variation in genes encoding enzymes involved in ATP regeneration or in other metabolic pathways potentially related to physical performance. Of particular interest in this report is the gene coding for muscle-specific creatine kinase (CKMM). Creatine kinase (CK) is a key enzyme in energy metabolism that catalyzes the following reaction: phosphocreatine + MgADP + H + [lrarr2] MgATP + creatine. This enzyme is