Purpose. The aim of the study was to determine the changes in maximal anaerobic power and work output observed in a 15-second maximal power ergometer test following a four to five week-long transition period in a group of young sprinters. Methods. Sixteen young sprinters (six women and ten men) were asked to perform a 15-second maximal power output cycle ergometer test (a modified variant of the standard Wingate test). Blood samples were obtained from subjects before the test and three minutes after exercise in order to measure lactate (LA), hydrogen ion (H+) and bicarbonate (HCO3 -) concentrations. The tests were conducted twice, at the beginning (T1) and the end (T2) of the transition period for each of the sprinters. Results. Changes in the body weight and the body fat content of the sprinters following the transition period were non-significant. When comparing pre- to post-transition period performance, there were no significant changes in total work output (Wtot) and maximal power (Pmax), however these parameters’ ratios to body weight were found to slightly increase in the group of males. A significant increase in the number of total pedal revolutions in males was also observed. There were no changes in the time of maintaining maximal power (Tm) and time to reach maximal power output (Tr) in both groups. No statistically significant changes in the values of the selected parameters LA, H+, HCO3 - and also the ratio of H+ to Wtot were noted between the tests performed at T1 and T2. Conclusion. The four to five week-long transition period did not diminish power and work performance in 15-second maximal power output test in young sprint athletes. Moreover, some of the performance parameters increased in the group of male sprinters.