Wayne L. Westcott

The Effects of Different Resistance Training Protocols on Muscular Strength and Endurance Development in Children

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 repetition–heavy 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 repetition–moderate 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.

Comparison of 1 and 2 days per week of strength training in children.

Abstract 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.

Effects of a 12-Week Physical Activity Protocol Delivered by YMCA After-School Counselors (Youth Fit For Life) on Fitness and Self-Efficacy Changes in 5–12-Year-Old Boys and Girls

Abstract To address reduced physical education (PE) in elementary schools, a 12-week physical activity protocol was tested on 5–12-year-old, primarily African American, girls (n= 226) and boys (n = 344) at 14 YMCA after-school care sites. The 3 times/week, 45-min session curriculum included cardiovascular, resistance, and flexibility training, in which all children could participate simultaneously, and a behavioral skills education component. After-school counselors, formerly untrained in PE methods, administered the sessions, with periodic supervision by YMCA wellness staff members. Analyses of the eight Age x Sex subsamples indicated significant improvements on body composition, strength, and endurance, both within-groups and when predicted changes due to maturation were accounted for. Exercise barriers self-efficacy significantly increased in subsamples of 9–10- and 11–12-year-old girls only. The need for replication across ethnic groups was suggested. Limitations and the need for extension of research on supplementation of elementary school PE were discussed.

Correlates of upper and lower body muscular strength in children.

Milliken, LA, Faigenbaum, AD, Loud, RL, and Westcott, W. Correlates of upper and lower body muscular strength in children. J Strength Cond Res 22: 1339-1346, 2008- 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 (R2 = 44.4% with age and gender not significant) and BMI and vertical jump were significant (R2 = 40.8% with age and gender not significant). Multiple regression analyses predicting CP 1RM showed that BMI and handgrip strength were significant (R2 = 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.

Effects of resistance training on protein utilization in healthy children.

PURPOSE Public health initiatives promote increased physical activity in children. More specifically, resistance training has recently received attention as an important component of youth fitness programs. The study examined the effect of this mode of exercise on protein utilization in young boys and girls. METHODS Healthy children (N = 11, 8.6 +/- 1.1 yr, 33.7 +/- 9.4 kg, 131 +/- 9.6 cm, BMI = 19.1 +/- 3.4) participated in a supervised resistance-training program 2 times.wk-1 for 6 wk. 15N glycine methodology was used to assess nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net turnover ([NET] = PS - PB) before (PRE) and after (POST) resistance training. Percent body fat (%BF), fat-free mass (FFM), fat mass (FM), and energy and protein intakes were also determined. PRE/POST measurements of 1RM for the chest press and leg extension were used to examine strength gains. RESULTS Gains associated with the chest press and leg extension were 10% and 75% (P < 0.001), respectively. Significant increases (P < 0.05) were noted for weight, height, FFM, and FM. Energy and protein intake remained constant. Significant decreases (PRE vs POST) were observed for Q (1.22 +/- 0.1 vs 0.75 +/- 0.05 gN.kg-1.d-1, P < 0.001), PS (6.48 +/- 0.47 vs 3.55 +/- 0.30 g.kg-1.d-1, P < 0.001), and PB (5.24 +/- 0.41 vs 2.96 +/- 0.30 g.kg-1.d-1, P < 0.01) after 6 wk of resistance training. NET was also reduced (P = 0.07, 1.24 +/- 0.31 vs 0.59 +/- 0.20 g.kg-1.d-1). CONCLUSIONS Resistance training resulted in a downregulation in protein metabolism, which may be energy based. Future studies are needed to clarify energy, as well as protein, needs in young children participating in this form of exercise.

Relationship Between Repetitions and Selected Percentages of the One Repetition Maximum in Healthy Children

The purpose of this study was to evaluate the relationship between repetitions and selected percentages of the one repetition maximum (RM) in apparently healthy children. The 1 RM strength was measured on 13 boys and eight girls (mean age 10.4 ± 1.2 years) on the Heartline chest press and the Nautilus leg press exercises. Subsequently, subjects were tested to determine the maximum number of repetitions that could be performed to volitional fatigue at 50% and 75% of their 1 RM for each exercise. The results for the trials on the leg press and chest press indicate that at 50% 1 RM, the subjects performed 87.2 ± 56.5 and 39.2 ± 19.4 repetitions, respectively, whereas at 75% 1 RM, the subjects performed 18.2 ± 11.0 and 13.4 ± 4.3 repetitions, respectively. As the percent 1 RM increased, it is not surprising that the number of repetitions performed significantly decreased (p < 0.05). However, the number of repetitions performed at 50% 1 RM on the leg press was significantly greater (p < 0.05) than at the same intensity on the chest press, suggesting that the number of repetitions performed at a given intensity may not be same for all exercises. Although additional study is warranted, these findings suggest that progressive resistive strengthening programs should be prescribed with a RM load as opposed to a percentage of the 1 RM.

Perceived Exertion during Resistance Exercise by Children

This pilot study examined the validity of a new scale of perceived exertion during acute bouts of resistance exercise in young children. The researchers developed an 11-point numerical scale with five pictures representing youths at various levels of exertion while lifting weights. 26 children (M age 10.1 ± 1.2 yr.) performed one set of 10 repetitions at 35%, 55%, and 75% of their one-repetition maximum on the chest press and leg press exercises using child-size weight training machines. Scaling procedures for the perceptual anchors on the perceived exertion scale were based on one repetition maximum testing. Children could use this scale to translate into numbers their perceptions of physical exertion during upper and lower body resistance exercise. Perceived exertion distributed as a positive linear function of the percent of one repetition maximum on the chest press and leg press exercises (rs = .70 to .77), and perceived exertion increased significantly across all three exercise intensities on both exercises. These preliminary findings provide partial evidence for validation when this scale was used during resistance exercise with children. Additional validation regarding perceived exertion during resistance exercise with children is warranted.

EFFECTS OF THE YOUTH FIT FOR LIFE PROTOCOL ON PHYSIOLOGICAL, PSYCHOLOGICAL, AND BEHAVIORAL FACTORS AT YMCA CALGARY AFTER-SCHOOL CARE SITES

Youth inactivity and inappropriately high weight is a problem in the United States, Canada, and much of the industrialized world. Physiological and behavioral changes associated with the Youth Fit For Life protocol, a physical activity and nutrition education treatment based on self-efficacy theory, were assessed in 7- to 12-yr.-olds (N = 43) from Calgary, Alberta, Canada. Body Mass Index, strength, and cardiorespiratory endurance significantly improved over a 12-wk. period when contrasted with changes based on normative data. Significant within-group improvements in measures of self-efficacy, vegetable intake, and voluntary moderate-to-vigorous physical activity were also found over 12 wk. Multiple regression analysis indicated that score changes in measures of self-regulatory and task self-efficacy, and general self, accounted for changes in voluntary physical activity. Implications for use of behaviorally based methods for large-scale obesity prevention treatments in preadolescents were discussed.

Comparison of Two Exercise Protocols on Fitness Score Improvement in Poorly Conditioned Air Force Personnel

A 12-wk. study was conducted to contrast the effects of a longer and more frequent aerobic exercise protocol with a shorter and less frequent circuit strength-training protocol for improving U.S. Air Force physical fitness test scores of subjects who previously failed to achieve a passing point total. 83 men and women of the U.S. Air Force (M age = 32.7 yr.) participated in either the unsupervised standard conditioning program, which recommended approximately 60 min. of aerobic activity 4 to 5 days per week (n = 26), or the supervised circuit strength-training program, which required approximately 25 min. of alternating strength and endurance exercises 3 days per week (n = 57). Subjects were assessed on a 2400-m (1.5-mile) run, abdominal circumference, push-ups completed in 1 min., and abdominal crunches completed in 1 min. Dependent t tests with Bonferroni adjustment indicated that significant improvements were attained by the circuit strength-training group only on each of the aforementioned measures. Significantly more participants in the circuit strength-training group (26%) achieved a passing point total than in the standard conditioning group (19%) at Wk. 12 (χ12 = 3.96, p = .05). Implications for enhancing physical fitness in poorly conditioned adults were discussed.

Relationship of feeling states after exercise and total mood disturbance over 10 weeks in formerly sedentary women

Changes in feeling states after exercise and changes in overall mood after a period of 10 weeks were correlated after participation in a supervised, moderate intensity resistance training program. 52 previously sedentary, asymptomatic women (M = 56 yr.) participated. Point biserial correlations were calculated between the 10-wk. change on the Profile of Mood States using the Total Mood Disturbance score as the continuous variable, and positive or negative change in feeling states after exercise, assessed via the Exercise-induced Feeling Inventory, being the dichotomous variable. Correlations were significant for both the total sample (rpb = −.49) and participants with high initial Total Mood Disturbance based on a median split (rpb = −.55). Participants with positive changes in their feeling states after exercise also showed a significantly greater decrease in Total Mood Disturbance than those with negative changes. Changes in Total Mood Disturbance were not significantly correlated with changes in resting heart rate over the 10 weeks. Discussion included limitations and, after replication, possible application of the findings.