The aim of our study was to determine changes in sport and motor performance of competitors in the category of children’s fitness as a result of conditioning training intervention. We conducted a two-group simultaneous experiment. Experimental group (EG) and control group (CG) consisted of 18 girls competing in the 12 to 15 years old age categories. EG performed supervised conditioning program over a period of 25 weeks with training frequency 3 times per week. Based on the results of physical tests, competitive and expert assessments of sport performance in the children’s fitness category we found significant effect of our conditioning program to increase sport and motor performance in the experimental group. Subsequently, these improvements could lead to success in domestic and international competitions where they occupied the leading positions. Significant relationships (EG = 19; CG = 10) were found between competitive and expert assessments as well as physical tests results, between expert and competitive assessments of physiques and routines. These changes manifested positively not only in the competitive assessment of the physique but also in the expert “blind“ assessment in the competitive discipline of the physique presentation in quarter turns where we observed significant improvements in the EG. Based on the obtained results we recommend to increase the ratio of conditioning training to gymnastic-dance training to 50 %, inclusion of strengthening and plyometric exercises into the training process and monitor regularly the level of general and specific abilities of the competitors in the individual mezocycles of the annual training cycle.