After the first measurements, participants were randomly and equally assigned to the swimming, the running, the cycling and the control groups. All exercise groups participated in sessions of 40-min per day, three days per week, for a period of 12 weeks. Each session began with a five minutes warm-up, continued with a main set of 30-min exercise at their individual target heart rate zone (60-70% of heart rate reserve), and finished with a five minute cool-down period. The individual target heart rate zone was determined according to the Guidelines for Exercise Testing and Prescription of American College of Sport Medicines [1]. Swimming exercises composed of front crawl swimming and kicking drills. During the main sets, the participants performed front-crawl swimming at their individual heart rate zones which were determined by the Karvonen formula [2]. Cyclers exercised between 60-80 repetition per minute (RPM) on an ergometer (Monark E 834, Varberg, Sweden), which was adjusted for each individual in order to maintain the target heart rate zone. The running group participants exercised on a treadmill with a 1.5 % incline. The speed of the treadmill was determined according to individual heart rate zone. Throughout the 12 weeks of training, Heart Rate Reserves (HRR) was held constant (60-70%) while the speed increased according to individual progression. Individuals of the control group were instructed not to participate in any organized or structured exercise during the 12 weeks of intervention.