A group of elite 400-m distance runners carrying different alleles of the polymorphic angiotensinconverting enzyme (ACE) gene participated in an experiment that included aerobic exercise accompanied by measurement of the heart rate (HR) before, during, and after the exercise. Upon determination of the genotype for the ACE gene, the athletes were divided into three subgroups, carrying the II, ID, and DD alleles of the ACE gene. All athletes performed the same exercise: 25 min of running at an HR of 165-170 beats/min. The runners with the II genotype ran a significantly (p < 0.01) longer distance than the runners with the ID and DD genotypes. After the exercise, the HR recovery was the fastest in the runners with the II genotype.