This paper studies the racing experience of Katinka Hosszu (Hungary), an elite level female swimmer, multiple world champion and world record holder in individual medley swimming. In 2012-2015 katinka Hosszu became a winner of FINA World Cups, multiple winner of European and World Championships, broke world records fifteen times, and realized her potential in main competitions of each micro-cycle. Our study showed that the number of competitions an athlete takes part in makes an impact on the stability of the sports achievements and duration of sports qualification within a long competitive period, which stimulates the growth in the number of sports achievements. Increased athletic performance during training macrocycle is statistically associated with the total number of starts, indicating the importance of quantitative characteristics of competitive practices to ensure the required pace of sports perfection activity. The paper presents the materials reflecting the volume of competitive practice of the above named Hungarian swimmer as compared with the activity of a top Russian swimmer, a leading Russian swimmer in 2012-2015 in individual medley. The study shows that Hosszu’s volume of racing practices increased annually and the partial volumes swum in competitive distances using different swimming techniques changed, which led to positive changes in 200m medley distance performance and helped the athlete set a world record in 2015. In comparison, the volume of swimming distances of the Russian swimmer was 6-11 times less and it decreased each year. Therefore, her results in 200m medley swimming distance were lower, as well as her performance at main competitions in each micro-cycle.