Linkage between a muscle-specific CK gene marker and VO2max in the HERITAGE Family Study

Purpose: We have reported a significant association between Tie,,, in the s edentary state and its response (Delta (V) over dot O-2max) to an endurance training program with a muscle-specific creatine kinase (CKMM) gene polymo rphism. The purpose of this study was to test the hypothesis of genetic lin kage between the same CKMM marker and (V) over dot O-2max in the sedentary state as well as Delta (V) over dot O-2max. Methods: Sib-pair linkage analy sis was performed on 277 full sib-pairs from 98 Caucasian nuclear families of the HERITAGE Family Study. (V) over dot O-2max was measured during cycle ergometry tests before and after 20 wk of endurance training. The CKMM pol ymorphism was detected by the polymerase chain reaction and digestion with the Ncol restriction enzyme. Results: Frequencies for the rare (1170 base p airs) and common(985 + 185 base pairs) alleles were 0.32 and 0.68, respecti vely. No significant linkage (t = -0.02, P = 0.49) was detected between the CKMM marker and the age and sex adjusted (V) over dot O-2max (mL.kg(-1).mi n(-1)) in the sedentary state. However, after adjustment of Delta (V) over dot O-2max for the effects of age, sex, initial (V) over dot O-2max and bod y mass, evidence for linkage between the CKMM locus and Delta (V) over dot O-2max was suggestive (P = 0.04). Conclusion: The present results provide f urther support for the notion that the CKMM gene, or some gene in close Lin kage disequilibrium with it, may contribute to individual differences in th e (V) over dot O-2max response to endurance training.