Arazi, H. et al.: EFFECTS OF CONCURRENT EXERCISE PROTOCOLS ... Kinesiology 43(2011) 2:107-114 1 EFFECTS OF CONCURRENT EXERCISE PROTOCOLS ON STRENGTH, AEROBIC POWER, FLEXIBILITY AND BODY COMPOSITION Hamid Arazi 1 , Hassan Faraji 2 , Mahdi Ghahremani Moghadam 1 and Ali Samadi 3 1 Faculty of Physical Education and Sport Science, University of Guilan, Rasht, Iran 2 Department of Physical Education and Sport Science, Islamic Azad University Marivan Branch, Marivan, Iran 3 Faculty of Physical Education and Sport Science, University of Tehran, Tehran, Iran Original scientific paper UDC 796.15.54:796.015.572-055.1 Abstract: In this study we evaluated the effect of concurrent resistance and endurance training on body composition, aerobic power and muscular endurance in college students and compared the two concurrent exercise protocols. Forty-two male students (22.02±1.91 years of age) were divided into three groups: Concurrent Distinct Endurance-Resistance (CDER), Concurrent Parallel Endurance-Resistance (CPER) and No Training controls (C). The subjects performed two training protocols per week for 12 weeks. In CDER group, resistance training and endurance training were performed on different days each week (two and two days per week). CPER group performed endurance and resistance training on the same days each week (two days per week). After a 12-week training period, fat-free mass, muscular strength [squat and bench press (kg)], muscular endurance [pull-ups and sit-ups (numbers)], aerobic power, flexibility and Sargent jump height increased similarly in both experimental groups (CDER and CPER). Also, decreases in body fat percentage, mean time in 60 m running and agility occurred in CDER and CPER. A significant difference in body fat percentage was seen in CPER when compared to CDER and C. Body mass increased significantly in CPER when compared to CDER and C. Although body mass increased only after the CPER protocol application, it can be concluded that both CDER and CPER protocols were similarly effective in positive transformation of body composition, aerobic power and muscular endurance. Key words: resistance training, endurance training, concurrent training, body mass, VO 2 max Introduction Some sports and sport events such as throwing events in track-and-field, are characterized by the demonstration of strength and high power outputs. In addition, many of the strength/power sports in- volve maximal efforts which must be repeated af- ter relatively short rest periods (Tanaka & Swensen, 1998). Thus, some strength and conditioning profes- sionals believe that the inclusion of aerobic endur- ance training may offer some benefits to strength/ power athletes (Baechle, 1994). Additionally, it is well documented that strength/power athletes may perform endurance exercises in order to maintain an optimal body weight or to reduce body fat levels (Dudley & Fleck, 1987). In the past two decades, concurrent resistance and endurance training programs have received much attention as a form of training. Several studies have shown that concurrent training (resistance and endurance training in the same session or program) interferes with the development of muscle strength or power (Chtara, et al., 2008; Nelson, Arnall, Loy, Silvester, & Conlee, 1990; Hennessy & Watson, 1994). On the other hand, some studies reported a compatibility of resistance and endurance training, and did not show any reduction in strength adapta- tions after concurrent strength and aerobic endur- ance training (Izquierdo, et al., 2004; Izquierdo, Hakkinen, Ibanez, Kraemer, & Gorostiaga, 2005; Glowacki, et al., 2004; Balabinis, Psarakis, Moukas, Vassiliou, & Behrakis, 2003). Furthermore, some studies demonstrate a positive effect of concurrent training on muscle strength (Gorostiaga, Izquierdo, Iturralde, Ruesta, & Ibanez, 1999; Davis, Wood, Andrews, ElkIind, & Davis, 2008a,b; Baker, 2001), muscle endurance (Hickson, Dvorak, Gorostiaga, Kurowski, & Forster, 1988; Kraemer, et al., 1995), maximal aerobic capacity (McCarthy, Agre, Graf, Pozniak, & Vailas, 1995; Kraemer, et al., 2001) and body composition (Garcia-Lopez, Galini, & Ha-