As the popularity of running is increasing, so is the increasing number of recreational runners and running schools. Recreational runners often do only one type of low intensity-high volume trainings. Because of it their aerobic and anaerobic energy capacity is mostly underdeveloped. Different training models need to be vigorously maintained. For this reason, a training program was created as a model which could be included in the standard recreational running program. The main objective of this study is to compare the impact of HIIT trainings, with different frequencies (1x and 3x per week) on a fitness level in recreational runners. The sample of volunteers consisted of fifteen (15) recreational runners which had already participated in the training program of a running school “Trčaona” (sex = female, age = 33.6 ± 7.1 years, body height = 168.1 ± 6.7 cm, body weight = 61.1 ± 5 , 2 kg). Each subject was measured in 34 anthropometric variables. The variables for energy capacities were obtained by the KF1 protocol test on a treadmill. Measurements were taken twice (initialy and finaly). The training program lasted for 8 weeks and the trainings were integrated within standard training sessions. The results in this study indicate that there are no statistically significant differences in fitness level for recreational runners who trained HIIT 3x per week versus the ones who traine 1x per week. Although there is no statistically significant difference, the training program (as expected) caused an improvement in fitness level and there is a tendency for progress in all the variables which were monitored. Also, all of the subjects in HIIT 3 group confirmed that their HIIT training, although more taxing, was more enjoyable than long-term endurance running.