Exercise is a great challenge for cardiovascular system and metabolism and can achieve different adaptive responses depending on the frequency, intensity, and type of physical activity and also on the age of individuals. Thus we hypothesized that the adaptations of cardiovascular, respiratory, nervous and hormonal systems will be different to the increased energy and oxygen requirements in different groups of people exposed to different physical activities. Thus we aimed to carry out these investigations in endurance athletes (EA), members of Counter Terrorism Center (CTC) and senior athletes (SA) because their training methods and ages of the three the groups are different according to the requirements of their professions. Endurance athletes (age: 24±5.9, n=8), members of Counter Terrorism Centre (age: 31±3.4, n=14) and senior athletes (age: 52±3, n=17) participated in the study. The study was approved by the Research Ethics Committee of ELTE University. In all groups, the body weight, body height, and exercise load were measured. The cardiorespiratory fitness was measured by Marquette-2000 treadmill (Pittsburgh, PA, USA) to maximal fatigue. The resting heart rate (beat/min, HRrest) and maximal heart rate (HRmax), were measured by “Cardiosoft”, (Milwaukee, USA), aerobic capacity (VO2max), ventilation (VE) (BTPS L x min-1) and its components were measured by Sensor Medics “Vmax 29C” (Yorba Linda, CA, USA). Statistical analysis was performed by Stat. Soft. 2013. Data are presented as mean±SEM. We have found a significant correlation between the average mean body weight of the groups (BWEA=72±7.5; BWCTC=84 ± 7.8; BWSA=84 ± 7.8kg). The exercise performance of the endurance athletes was the greatest (451±49 W). The relative aerobic capacity measured at the peak of the exercise performance of endurance athletes was 3 ml x kg-1 x min-1 higher than that of the members of Counter Terrorism Centre (RVO2maxEA = 59.1±9.2 mL x kg-1 x min-1; RVO2maxCTC = 56.4±6.6 mL x kg-1 x min-1. These values differed significantly from each other at the anaerobic threshold (RVO2maxEA = 56±8.6; RVO2maxCTC = 46.02±5.4, p<0.05). The maximum heart rate corresponded to the age characteristics (HRmaxEA=190.8±9.2; HRmaxCTC=183.4 ± 10.95; HRmaxSA=153.4 ± 17.3 beat x min1 p<0.05). The volume of ventilation of the first two groups reached 150 L x min-1, whereas the normalized ventilation values to body mass showed significant differences (RVEEA=2.1 ± 0.2; RVECTC=1.79 ± 0.2). Thus the exercise performance of endurance athletes and senior athletes depend primarily on aerobic metabolism, whereas the members of Counter Terrorism Centre due to their special exercise training have greater anaerobic energy support to achieve their exercise performance. In contrast, their cardiorespiratory performance was lower than that of endurance athletes. Interestingly, however – in some individuals – extreme load-induced changes in physiological parameters were group-independent.