Regular aerobic and anaerobic physical activity programs have a positive effect on the overall health of the individual, especially muscular and cardiorespiratory endurance. Cardiorespiratory endurance implies high-quality work of the cardiovascular and respiratory systems, and one of the best measures of its development is maximum oxygen intake. High-intensity interval training is a type of training that can significantly improve cardiorespiratory endurance but also lead to a reduction in subcutaneous fat. Nowadays, a large number of athletes and recreationists use various supplements to improve sports performance and delay the onset of fatigue, and one of them is the carnosine supplement. The main goal of this thesis was to examine the statistical significance of differences in changes in morphological characteristics and maximum oxygen intake under the influence of interval training and with the use of carnosine supplements in two groups of subjects. The research was conducted on 23 healthy sedentary students from Josip Juraj Strossmayer University in Osijek and Lavoslav Ružički Polytechnic in Vukovar. By random selection, the subjects were divided into two experimental groups. The first group implemented an interval running program, while the second group consumed 500 g of carnosine on a daily basis in addition to the training program. The difference between initial and final measurements in both groups of subjects was tested using the t test for independent samples. Analyzing the differences between the initial and final measurements of the first experimental group, no statistically significant differences in morphological changes were found, while in the case of maximum oxygen uptake, they were determined at the level of p<0.001. In the second experimental group, at the p<0.05 level, statistically significant differences were found in changes in morphological characteristics: body weight, back skinfold and waist circumference, and at the p<0.001 level, in the maximum oxygen intake. The obtained results of this research confirm that beta-alanine supplementation with a properly programmed training program can have a positive effect on reducing body weight and the amount of fat tissue.