ABSTRACT
Muscular tness includes parameters of strength, endurance, and power (American College of Sports Medicine [ACSM], 2011) and is one of the four components of tness (ACSM, 2010). Muscle strength may be dened as the maximum mechanical torque or force generated by skeletal muscle or muscle groups (Sti, 2001); muscular endurance indicates an ability to maintain force for longer durations (Alberga, Sigal, & Kenny, 2011; Bar-Or & Rowland, 2004; Heyward, 2002) and an ability to perform repeated muscular contractions using high resistance (Pate, 1991). e number of motor units activated over a specic time and the crosssectional area of the contracting muscle(s) determine the potential for increasing muscular strength and endurance (Bar-Or & Rowland, 2004). Explosive strength or power is dened as performance of work expressed per unit of time or the maximum amount of force produced in the shortest time frame (Bar-Or & Rowland, 2004; Hakkinen et al., 1985). Programs to improve muscular power must include a rapid speed component specic to the desired goals, which typically are related to the improvement of sports performance (Ratamess et al., 2009; ompson et al., 2010). It is essential that children, and in particular, overweight and obese children, participate in exercise activities that promote the attainment of muscular strength and endurance (U.S. Department of Health and Human Services [U.S. DHHS], 2008). e ability to participate in daily physical activities is limited in children with weak muscles. Research supports the concept that, if properly administered, strength or resistance-training programs not only may be safe in youth but also may promote enhanced motor performance (Behringer et al., 2011) and help reduce the risk of injury during other physical activities (Faigenbaum & Myer, 2010); however, these benets are realized only if close supervision is provided by trained, qualied instructors (Ganley et al., 2011). e ACSM (2010, 2011), the National Strength and Conditioning Association (Faigenbaum et al., 2009), and the American Academy of Pediatrics (AAP, Committee on Sports Medicine, 1990; Washington et al., 2001) have all published statements in support of properly administered and supervised, developmentally appropriate muscular strength and endurance training in children and adolescents. It is suggested that a child be of a sucient age to participate in sports activities before engaging in structured exercise to specically improve muscular strength and endurance, which is typically 7 –8 years of age (Faigenbaum et al., 2009). Resistance training provides the optimal method of developing the components of muscular strength and endurance in children and adolescents. Resistance training is dened as a type of physical conditioning using varied types of training apparatus, including free weights, weight machines, medicine balls, elastic bands, or one’s own body weight as resistance (Alberga et al., 2011), which provides progressively increasing resistive loads and diering movement velocities (Faigenbaum & Myer, 2010). e term “resistance exercise” oen is used interchangeably with the terms “strength training” or “weight training” (Alberga et al., 2011). It is important, however, that resistance training not be confused with the sports of body-building, weightliing, and power liing, as the goals of these activities are to increase muscle size or improve the amount of maximal weight that can be lied during a competition. e two types of resistance training are (1) traditional weight training and (2) plyometric exercise.
