ABSTRACT. Background. Previous research has shown that children can increase their muscular strength and muscular endurance as a result of regular participation in a progressive resistance training program. However, the most effective exercise prescription regarding the number of repetitions remains questionable.Objective. To compare the effects of a low repetitionheavy load resistance training program and a high repetition-moderate load resistance training program on the development of muscular strength and muscular endurance in children.Design. Prospective, controlled trial. Setting. Community-based youth fitness center. Subjects. Eleven girls and 32 boys between the ages of 5.2 and 11.8 years.Intervention. In twice-weekly sessions of resistance training for 8 weeks, children performed 1 set of 6 to 8 repetitions with a heavy load (n ‫؍‬ 15) or 1 set of 13 to 15 repetitions with a moderate load (n ‫؍‬ 16) on child-size exercise machines. Children in the control group (n ‫؍‬ 12) did not resistance train. One repetition maximum (RM) strength and muscular endurance (repetitions performed posttraining with the pretraining 1-RM load) were determined on the leg extension and chest press exercises.Results. One RM leg extension strength significantly increased in both exercise groups compared with that in the control subjects. Increases of 31.0% and 40.9%, respectively, for the low repetition-heavy load and high repetition-moderate load groups were observed. Leg extension muscular endurance significantly increased in both exercise groups compared with that in the control subjects, although gains resulting from high repetitionmoderate load training (13.1 ؎ 6.2 repetitions) were significantly greater than those resulting from low repetition-heavy load training (8.7 ؎ 2.9 repetitions). On the chest press exercise, only the high repetition-moderate load exercise group made gains in 1-RM strength (16.3%) and muscular endurance (5.2 ؎ 3.6 repetitions) that were significantly greater than gains in the control subjects.Conclusion. These findings support the concept that muscular strength and muscular endurance can be improved during the childhood years and favor the prescription of higher repetition-moderate load resistance training programs during the initial adaptation period. Pediatrics 1999;104(1). URL: http://www.pediatrics.org/ cgi/content/full/104/1/e5; strength training, weight training, exercise, youth, preadolescent.ABBREVIATIONS. RM, repetition maximum; DCER, dynamic constant external resistance. I n the past several years, resistance training has proven to be a safe and effective method of conditioning for children, provided that appropriate exercise guidelines are followed.1-3 Although the capability of children to increase their muscular strength was questioned in the past, 4 current findings suggest that children may benefit from regular participation in resistance training activities. Reports indicate that youth resistance training may improve motor performance skills, 5 may reduce injuries in sports and recre...

Despite the widespread use of and acceptance of muscular fitness field tests in national youth fitness test batteries, little is known about how these field tests compare to 1 repetition maximum (1RM) strength in children. Therefore, the aim of this study was to characterize and identify correlates of muscular strength in children 7 to 12 years of age. Ninety children (39 girls and 51 boys) between the ages of 6.7 and 12.3 years volunteered to participate in this study. Children were tested on 1RM chest press (CP) strength, 1RM leg press (LP) strength, handgrip strength, vertical jump, long jump, sit and reach flexibility, and height and weight (used to determine body mass index [BMI]). For the combined sample, LP 1RM ranged from 75% to 363% of body weight and CP 1RM ranged from 25% to 103% of body weight. Multiple regression analyses predicting LP 1RM showed that BMI and long jump were significant (R = 44.4% with age and gender not significant) and BMI and vertical jump were significant (R = 40.8% with age and gender not significant). Multiple regression analyses predicting CP 1RM showed that BMI and handgrip strength were significant (R = 58.6% with age and gender not significant). Age and gender alone accounted for 4.6% (not significant) of the variation in LP 1RM and 15.4% (significant) in CP 1RM. In summary, these data indicate that BMI, handgrip strength, long jump, and vertical jump relate to 1RM strength in children and therefore may be useful for assessing muscular fitness in youths.

The purpose of this study was to compare the effects of 1 and 2 days per week of strength training on upper body strength, lower body strength, and motor performance ability in children. Twenty-one girls and 34 boys between the ages of 7.1 and 12.3 years volunteered to participate in this study. Participants strength trained either once per week (n = 22) or twice per week (n = 20) for 8 weeks at a community-based youth fitness center. Each training session consisted of a single set of 10-15 repetitions on 12 exercises using child-size weight machines. Thirteen children who did not strength train served as age-matched controls. One repetition maximum (1RM) strength on the chest press and leg press, handgrip strength, long jump, vertical jump, and flexibility were assessed at baseline and posttraining. Only participants who strength trained twice per week made significantly greater gains in 1RM chest press strength, compared to the control group (11.5 and 4.4% respectively, p < .05). Participants who trained once and twice per week made gains in 1RM leg press strength (14.2 and 24.7%, respectively) that were significantly greater than control group gains (2.4%). On average, participants who strength trained once per week achieved 67% of the 1RM strength gains. No significant differences between groups were observed on other outcome measures. These findings support the concept that muscular strength can be improved during the childhood years and favor a training frequency of twice per week for children participating in an introductory strength training program.

This study examined the effects of 4 different resistance training protocols on upper-body strength and local muscle endurance development in children. Untrained boys and girls (mean +/- SD age, 8.1 +/- 1.6 years) trained twice per week for 8 weeks using child-sized weight machines and medicine balls weighing 1-2.5 kg. In addition to general conditioning exercises, subjects in each exercise group performed 1 set of the following exercise protocols for upper-body conditioning: 6-8 repetitions with a heavy load on the chest press exercise (HL, n = 15); 13-15 repetitions with a moderate load on the chest press exercise (ML, n = 16); 6-8 repetitions with a heavy load on the chest press exercise immediately followed by 6-8 medicine ball chest passes (CX, n = 12); or 13-15 medicine ball chest passes (MB, n = 11). Twelve children served as nontraining controls (CT). After training, only the ML and CX groups demonstrated significant (p < 0.05) improvements in 1RM chest press strength (16.8% and 16.3%, respectively) as compared with the CT group. Local muscle endurance, as determined by the number of repetitions performed posttraining on the chest press exercise with the pretraining 1RM load, significantly increased in the ML group (5.9 +/- 3.2 repetitions) and CX group (5.2 +/- 3.6 repetitions) as compared with the CT group. In terms of enhancing the upper-body strength and local muscle endurance of untrained children, these findings favor the prescription of higher-repetition training protocols during the initial adaptation period.

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