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In recent years several genetic polymorphisms related to the GH-IGF-I axis were suggested to promote athletic excellence in endurance and power sports. We studied the presence of the C-1245T SNP (rs35767), a nucleotide substitution in the promoter region of the IGF-I gene, and the presence of the 275124A > C SNP (rs1464430), a common nucleotide substitution in the intron region of the IGF-I receptor (IGF-IR) gene in elite long and short-distance swimmers compared with nonphysically active controls. The rare T/T IGF-I polymorphism was found only in 5.3% of the long-distance swimmers, and was not found at all in the short-distance swimmers or among the control group participants. The prevalence of the IGF-I receptor AA genotype was significantly lower in the swimming group as a whole (35%) compared with the control group (46%), in particularly due to reduced frequency of the AA genotype among short-distance swimmers (26%). In contrast to previous reports in elite endurance and power track and field athletes, single nucleotide polymorphisms of the IGF-I and the IGF-IR were not frequent among elite Israeli short- and long-distance swimmers emphasizing the importance of other factors for excellence in swimming. The results also suggest that despite seemingly similar metabolic characteristics different sports disciplines may have different genetic polymorphisms. Thus, combining different disciplines for sports genetic research purposes should be done with extreme caution.

The aim of the study was to assess whether an aerobic-favoring genetic profile can predict the success of a shift from middle- to long-distance running. Thirteen elite middle-distance runners were divided into successful and nonsuccessful groups in their shift toward long-distance runs. All the runners began their training program at the age of 14-15, and after 6-7 years, changed focus and adjusted their training program to fit longer running distances. The participants' personal records in the longer events were set at the age of 25-27, about 3-5 years after the training readjustment took place. The endurance genetic score based on 9 polymorphisms was computed as the endurance genetic distance score (EGDS9). The power genetic distance score (PGDS5) was computed based on 5 power-related genetic polymorphisms. The mean EGDS9 was significantly higher among the successful group than the nonsuccessful group (37.1 and 23.3, respectively, p < .005, effect size 0.75), while the mean PGDS5 was not statistically different between the 2 groups (p = .13). Our findings suggest the possible use of genetic profiles as an added tool for determining appropriate competitive transition and specialization in young athletes involved in early phases of talent development.