Fitness-related benefits result in essential changes in physical fitness level in young women. This study was conducted with fitness centre clients (35 women with an average age of 26.4±2.2 years). The results of the experiment made it possible to evaluate the short-term response of the body to the training loads of different intensities in different blocks of the training session. The following six main blocks were distinguished in the structure of the exercise sessions including: aerobic, dance, variable, corrective, warm-up, and relaxation; and two additional ones. The aerobic and dance blocks were characterized by the highest intensity: HRav was 75.6±1.71% of HRmax, VO2 was 63.5±1.64% of VO2max, and energy expenditure (EE) was ranged from 465.28 to 524.36 kcal/hour. The relaxation block had the low- est intensity: HR was 57.31±0.56% of HRmax, VO2 was 34.2±6.25% of VO2max, and EE was of 252.6±49.24 kcal/h. We found that the percentage contribution of fats to energy production was higher in the warm-up (78.24%), relaxation (68.93%), and corrective (42.65%) blocks. The largest percentage of CHO utilization for energy metabolism was found in additional (92.8%), variable (91.82%), and dance (86.54%) blocks. The data obtained allowed to experimentally substantiate and methodologically structure a number of fitness means used in exercise sessions, by dividing them into specialized blocks that made it possible to selectively effect on different components of the physical condition.
