Preliminary evaluation of an after-school resistance training program for improving physical fitness in middle school-age boys

Reporting of Adverse Events in Muscle Strengthening Interventions in Youth: A Systematic Review

Clear definition, identification, and reporting of adverse event (AE) monitoring during training interventions are essential for decision making regarding the safety of training and testing in youths.

PURPOSE

To document the extent to which AEs, resulting from intervention studies targeting muscle strengthening training (MST) in youth, are reported by researchers.

METHODS

Electronic databases (CINAHL, PubMed, SPORTDiscus, and Web of Science) were searched for English peer-reviewed articles published before April 2018. Inclusion criteria were: (1) average age <16 years, (2) use of MST, (3) statement(s) linked to the presence/absence of AEs, and (4) randomized controlled trials or quasi-experimental designs. Risk of reporting bias for AEs followed recommendations by the Cochrane Collaboration group.

RESULTS

One hundred and ninety-one full-text articles were screened. One hundred and thirty met all MST criteria, out of which only 44 (33.8%; n = 1278, age = 12.1 [1.1] y) included a statement as to the presence/absence of adverse events. The 86 other studies (66.2%) included no such statement. Of the reporting 44 studies, 18 (40.1%) indicated one or more adverse events. Of the 93 reported adverse events, 55 (59.1%) were linked to training or testing.

CONCLUSIONS

Most MST studies in youth do not report presence/absence of adverse events, and when reported, adverse events are not well defined.

Influence of Strength Training Variables on Neuromuscular and Morphological Adaptations in Prepubertal Children: A Systematic Review

Strength training in prepubertal children is one of the topics that has aroused the most interest and controversy among training professionals in recent years. Therefore, the aim of the present study was to analyze the available scientific evidence on the influence of strength training variables on morphological and/or neuromuscular adaptations in healthy prepubertal populations with no previous experience in this type of training according to the descriptive sample characteristics. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis, 22 studies were selected after a systematic search and selection process using four electronic databases: Google Scholar, PubMed, Scopus, and SPORT Discus. Furthermore, the internal validity of the studies included was assessed using the modified PEDro scale. The sample consisted of 604 prepubertal children (age, 10.02 ± 0.75 years), of whom 473 were boys and 131 were girls, with 104 strength training programs recorded. Strength training resulted in a significant increase in jumping (n = 29) and sprinting (n = 13) abilities. Moreover, muscle strength was increased in 100% of the cases. Morphologically, strength training resulted in a decrease in body fat percentage (n = 19) and an increase in lean body mass (n = 17). With regard to gender, increases in general sport skills and basic physical abilities were significant in males but not in females. Thus, the results are more heterogeneous in girls due to the small number of studies carried out. Therefore, this research provides practical applications for coaches to design and implement more effective training programs to maximize adaptations, enhance physical performance, and reduce injury risk.

Acute Effects of Different Plyometric and Strength Exercises on Balance Performance in Youth Weightlifters

Background: High-intensity muscle actions have the potential to temporarily improve the performance which has been denoted as postactivation performance enhancement. Objectives: This study determined the acute effects of different stretch-shortening (fast vs. low) and strength (dynamic vs. isometric) exercises executed during one training session on subsequent balance performance in youth weightlifters. Materials and Methods: Sixteen male and female young weightlifters, aged 11.3±0.6years, performed four strength exercise conditions in randomized order, including dynamic strength (DYN; 3 sets of 3 repetitions of 10 RM) and isometric strength exercises (ISOM; 3 sets of maintaining 3s of 10 RM of back-squat), as well as fast (FSSC; 3 sets of 3 repetitions of 20-cm drop-jumps) and slow (SSSC; 3 sets of 3 hurdle jumps over a 20-cm obstacle) stretch-shortening cycle protocols. Balance performance was tested before and after each of the four exercise conditions in bipedal stance on an unstable surface (i.e., BOSU ball with flat side facing up) using two dependent variables, i.e., center of pressure surface area (CoP SA) and velocity (CoP V). Results: There was a significant effect of time on CoP SA and CoP V [F(1,60)=54.37, d=1.88, p<0.0001; F(1,60)=9.07, d=0.77, p=0.003]. In addition, a statistically significant effect of condition on CoP SA and CoP V [F(3,60)=11.81, d=1.53, p<0.0001; F(3,60)=7.36, d=1.21, p=0.0003] was observed. Statistically significant condition-by-time interactions were found for the balance parameters CoP SA (p<0.003, d=0.54) and CoP V (p<0.002, d=0.70). Specific to contrast analysis, all specified hypotheses were tested and demonstrated that FSSC yielded significantly greater improvements than all other conditions in CoP SA and CoP V [p<0.0001 (d=1.55); p=0.0004 (d=1.19), respectively]. In addition, FSSC yielded significantly greater improvements compared with the two conditions for both balance parameters [p<0.0001 (d=2.03); p<0.0001 (d=1.45)]. Conclusion: Fast stretch-shortening cycle exercises appear to be more effective to improve short-term balance performance in young weightlifters. Due to the importance of balance for overall competitive achievement in weightlifting, it is recommended that young weightlifters implement dynamic plyometric exercises in the fast stretch-shortening cycle during the warm-up to improve their balance performance.

Development and Content Validity of the Physical Activity Questionnaire-Young Children (PAQ-YC) to Assess Physical Activity in Children between 5 and 7 Years

Childhood is a critical period in the development and consolidation of healthy habits, such as the practice of physical activity (PA). It is essential to have valid instruments to measure PA from an early age. The aim of this study was to design and evaluate the content validity of the Physical Activity Questionnaire-Young Children (PAQ-YC) to measure the PA level in children aged 5-7 years. The first version of the questionnaire was tested by a 2-round Delphi study. It was established as a consensus criterion that the relative interquartile range (RIR) and/or the coefficient of variation (CV) were ≤20%. The most significant discrepancies in the Delphi survey (n = 11-13) were observed for items about hours of Physical Education or similar activities at school (item 7: RIR = 20, CV = 38.73) and for items about participation in Physical Education (item 8: RIR = 25, CV = 15.45). The cognitive interviews (n = 5) confirmed the version agreed by the experts. The results show that the PAQ-YC presents adequate content validity in terms of relevance, comprehensiveness and comprehensibility.

The Case for Retiring Flexibility as a Major Component of Physical Fitness

Flexibility refers to the intrinsic properties of body tissues that determine maximal joint range of motion without causing injury. For many years, flexibility has been classified by the American College of Sports Medicine as a major component of physical fitness. The notion flexibility is important for fitness has also led to the idea static stretching should be prescribed to improve flexibility. The current paper proposes flexibility be retired as a major component of physical fitness, and consequently, stretching be de-emphasized as a standard component of exercise prescriptions for most populations. First, I show flexibility has little predictive or concurrent validity with health and performance outcomes (e.g., mortality, falls, occupational performance) in apparently healthy individuals, particularly when viewed in light of the other major components of fitness (i.e., body composition, cardiovascular endurance, muscle endurance, muscle strength). Second, I explain that if flexibility requires improvement, this does not necessitate a prescription of stretching in most populations. Flexibility can be maintained or improved by exercise modalities that cause more robust health benefits than stretching (e.g., resistance training). Retirement of flexibility as a major component of physical fitness will simplify fitness batteries; save time and resources dedicated to flexibility instruction, measurement, and evaluation; and prevent erroneous conclusions about fitness status when interpreting flexibility scores. De-emphasis of stretching in exercise prescriptions will ensure stretching does not negatively impact other exercise and does not take away from time that could be allocated to training activities that have more robust health and performance benefits.

Sport-Specific Assessment of the Effectiveness of Neuromuscular Training in Young Athletes

Neuromuscular training in young athletes improves performance and decreases the risk of injuries during sports activities. These effects are primarily ascribed to the enhancement of muscle strength and power but also balance, speed and agility. However, most studies have failed to demonstrate significant improvement in these abilities. This is probably due to the fact that traditional tests do not reflect training methods (e.g., plyometric training vs. isometric or isokinetic strength testing, dynamic balance training vs. static balance testing). The protocols utilized in laboratories only partially fulfill the current needs for testing under sport-specific conditions. Moreover, laboratory testing usually requires skilled staff and a well equipped and costly infrastructure. Nevertheless, experience demonstrates that high-technology and expensive testing is not the only way to proceed. A number of physical fitness field tests are available today. However, the low reliability and limited number of parameters retrieved from simple equipment used also limit their application in competitive sports. Thus, there is a need to develop and validate a functional assessment platform based on portable computerized systems. Variables obtained should be directly linked to specific features of particular sports and capture their complexity. This is essential for revealing weak and strong components of athlete performance and design of individually-tailored exercise programs. Therefore, identifying the drawbacks associated with the assessment of athlete performance under sport-specific conditions would provide a basis for the formation of an innovative approach to their long-term systematic testing. This study aims (i) to review the testing methods used for the evaluation of the effect of neuromuscular training on sport-specific performance in young athletes, (ii) to introduce stages within the Sport Longlife Diagnostic Model, and (iii) to propose future research in this topic. Analysis of the literature identified gaps in the current standard testing methods in terms of their low sensitivity in discriminating between athletes of varied ages and performance levels, insufficent tailoring to athlete performance level and individual needs, a lack of specificity to the requirements of particular sports and also in revealing the effect of training. In order to partly fill in these gaps, the Sport Longlife Diagnostic Model was proposed.

Adaptations Associated With an After-School Strength and Conditioning Program in Middle-School-Aged Boys: A Quasi-Experimental Design

High-intensity strength and conditioning programs aimed at improving youth performance are becoming increasingly prevalent. The purpose of this study was to investigate the effects of a 16-week after-school strength and conditioning program on performance and body composition in middle-school-aged boys. Subjects in the training group (n = 16, mean age = 11.8 years) performed 90 minutes of supervised plyometric and resistance training twice weekly for 16 weeks. A group of control subjects (n = 9, age = 12.1 years) maintained their current activity levels. Sprint speed, 5-10-5 proagility, jump height, isometric peak torque of the leg extensors and flexors, and dual energy x-ray absorptiometry-derived body composition were examined during pretesting and posttesting. Data were analyzed by performing independent samples t-tests on the absolute change scores between groups. The primary findings were that the training intervention elicited significant improvements in 20-m sprint times (p = 0.03; mean change for training group = -0.17 seconds) and body-fat percentage (p = 0.03; 2.5% absolute improvement), the latter of which was a function of reduced fat mass (p = 0.06; -0.84 kg). Between-group differences were not noted for agility, jump height, lean mass, or strength measures; however, effect sizes generally showed greater improvements for the training group. In contrast to findings in longitudinal studies performed in collegiate athletes, sprint speed may be particularly adaptable during adolescence. In addition to potentially improving sport performance, high-intensity plyometric and resistance training programs offer the added benefit of improved body composition. These programs appear less effective for agility and jump performance and do not elicit substantial improvements in muscle mass above maturation.

Effectiveness of Traditional Strength vs. Power Training on Muscle Strength, Power and Speed with Youth: A Systematic Review and Meta-Analysis

Numerous national associations and multiple reviews have documented the safety and efficacy of strength training for children and adolescents. The literature highlights the significant training-induced increases in strength associated with youth strength training. However, the effectiveness of youth strength training programs to improve power measures is not as clear. This discrepancy may be related to training and testing specificity. Most prior youth strength training programs emphasized lower intensity resistance with relatively slow movements. Since power activities typically involve higher intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics), there is a conflict between the training medium and testing measures. This meta-analysis compared strength (e.g., training with resistance or body mass) and power training programs (e.g., plyometric training) on proxies of muscle strength, power, and speed. A systematic literature search using a Boolean Search Strategy was conducted in the electronic databases PubMed, SPORT Discus, Web of Science, and Google Scholar and revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for inclusion in this systematic review and meta-analysis. The meta-analysis showed small to moderate magnitude changes for training specificity with jump measures. In other words, power training was more effective than strength training for improving youth jump height. For sprint measures, strength training was more effective than power training with youth. Furthermore, strength training exhibited consistently large magnitude changes to lower body strength measures, which contrasted with the generally trivial, small and moderate magnitude training improvements of power training upon lower body strength, sprint and jump measures, respectively. Maturity related inadequacies in eccentric strength and balance might influence the lack of training specificity with the unilateral landings and propulsions associated with sprinting. Based on this meta-analysis, strength training should be incorporated prior to power training in order to establish an adequate foundation of strength for power training activities.

Feasibility and Parental Acceptability of an 8-Week, Slow-Speed, High-Intensity, Community-Based Resistance Training Program for Preadolescent Children

High-intensity resistance training (RT) shows promise for improved cardiometabolic health in children. Achieving high-intensity RT safely is a challenge for community-based programs because of parental concerns and group engagement. Twenty preadolescent children completed an 8-week, twice per week program using slow speed to achieve high-intensity RT. Parent and child surveys were conducted to measure acceptability and effectiveness. Child fitness levels were assessed, and fasting blood draws and dual-energy x-ray absorptiometry were performed on a subset population. Perceived RT safety, self-efficacy, body composition, waist circumference, and fitness tests exhibited significant improvements. Using slow speed to achieve high-intensity RT may provide a safe and effective community-based alternative for preadolescents.

Improving health-related fitness in adolescents: the CrossFit Teens™ randomised controlled trial

The aim of this study was to evaluate the preliminary efficacy and feasibility of the CrossFit Teens™ resistance training programme for improving health-related fitness and resistance training skill competency in adolescents. This assessor-blinded randomised controlled trial was conducted in one secondary school in the Hunter Region, Australia, from July to September 2013. Ninety-six (96) students (age = 15.4 (.5) years, 51.5% female) were randomised into intervention (n = 51) or control (n = 45) conditions for 8-weeks (60 min twice per week). Waist circumference, body mass index (BMI), BMI-Z score (primary outcomes), cardiorespiratory fitness (shuttle run test), muscular fitness (standing jump, push-up, handgrip, curl-up test), flexibility (sit and reach) and resistance training skill competency were measured at baseline and immediate post-intervention. Feasibility measures of recruitment, retention, adherence and satisfaction were assessed. Significant group-by-time intervention effects were found for waist circumference [-3.1 cm, P < 0.001], BMI [-1.38 kg · m(‒)(2), P < 0.001], BMI-Z [-0.5 z-scores, P < 0.001], sit and reach [+3.0 cm, P < 0.001], standing jump [+0.1 m, P = 0.021] and shuttle run [+10.3 laps, P = 0.019]. Retention rate was 82.3%. All programme sessions were delivered and participants' mean satisfaction scores ranged from 4.2 to 4.6 out of 5. The findings demonstrate that CrossFit Teens™ is a feasible and efficacious programme for improving health-related fitness in adolescents.

Comparison of resistance training progression models on maximal strength in sub-elite adolescent rugby union players

OBJECTIVES

To determine changes in maximal strength between two different resistance training progression models, linear (LP) and daily undulating (DUP), over a 12-week resistance training programme in sub-elite adolescent rugby union players.

DESIGN

The study used a quasi-experimental study design. Following baseline assessments, participants from Squad 1 were randomised to either LP or DUP; participants from Squad 2 formed a non-randomised comparison group (CON).

METHODS

Participants were 26 sub-elite adolescent rugby union players who were assessed at baseline and after 12 weeks. Outcomes included 5 repetition maximum (RM) box squat and bench press, height, body weight, skeletal muscle mass, percentage body fat and maturation status.

RESULTS

Participants in both the LP and DUP groups significantly increased their squat and bench press strength from baseline to 12 weeks. There were no significant differences between groups for squat and bench press increases after 12 weeks (p>0.05). No significant increases in squat or bench press strength were observed after 12 weeks in the CON group. Increases in lower body strength were large in the LP group (ES: 1.64) and very large in the DUP group (ES: 2.33). Upper body strength changes were small in both groups (LP, ES: 0.57; DUP, ES: 0.31).

CONCLUSIONS

Twelve weeks of LP or DUP resistance training are both effective at increasing maximal lower and upper body strength in adolescent rugby athletes. Additionally, twice weekly frequency of resistance training in adolescent rugby athletes with greater than 6-months resistance training experience is sufficient to elicit substantial increases in maximal strength.

Canadian Society for Exercise Physiology position stand: Benefit and risk for promoting childhood physical activity

Current guidelines recommend children accumulate 60 min of daily physical activity; however, highly publicized sudden-death events among young athletes raise questions regarding activity safety. An expert group convened (June 2012) to consider the safety of promoting increased physical activity for children, and recommended the publication of an evidence-based statement of current knowledge regarding the benefits and risks of physical activity for children. Recommendations for encouraging physical activity while maximizing the opportunity to identify children who have been prescribed a physical activity restriction include (1) professionals and (or) researchers that encourage children to change the type of physical activity or to increase the frequency, intensity, or duration of their activity should inquire whether a child has primary healthcare provider-prescribed activity limitations before the child’s activity participation changes; (2) physical activity researchers should prioritize the development of evidence regarding the benefits and risks of childhood physical activity and inactivity, particularly data on the risks of sedentary lifestyles and physical activity-associated injury risks that accounts for the amount of activity performed, and the effectiveness of current risk-management strategies and screening approaches; (3) professionals and researchers should prioritize the dissemination of information regarding the benefits of physical activity and the risks of sedentary behaviour in children; and (4) parents and professionals should encourage all children to accumulate at least 60 min of physical activity daily. The recommendations are established as a minimum acceptable standard that is applicable to all physical activity opportunities organized for children, whether those opportunities occur in a community, school, or research setting.

Effects on strength, power, and flexibility in adolescents of nonperiodized vs. daily nonlinear periodized weight training

The aim of this study was to compare 2 models of resistance training (RT) programs, nonperiodized (NP) training and daily nonlinear periodized (DNLP) training, on strength, power, and flexibility in untrained adolescents. Thirty-eight untrained male adolescents were randomly assigned to 1 of 3 groups: a control group, NP RT program, and DNLP program. The subjects were tested pretraining and after 4, 8, and 12 weeks for 1 repetition maximum (1RM) resistances in the bench press and 45° leg press, sit and reach test, countermovement vertical jump (CMVJ), and standing long jump (SLJ). Both training groups performed the same sequence of exercises 3 times a week for a total of 36 sessions. The NP RT consisted of 3 sets of 10-12RM throughout the training period. The DNLP training consisted of 3 sets using different training intensities for each of the 3 training sessions per week. The total volume of the training programs was not significantly different. Both the NP and DNLP groups exhibited a significant increase in the 1RM for the bench press and 45° leg press posttraining compared with that pretraining, but there were no significant differences between groups (p ≤ 0.05). The DNLP group's 1RM changes showed greater percentage improvements and effect sizes. Training intensity for the bench press and 45° leg press did not significantly change during the training. In the CMVJ and SLJ tests, NP and DNLP training showed no significant change. The DNLP group showed a significant increase in the sit and reach test after 8 and 12 weeks of training compared with pretraining; this did not occur with NP training. In summary, in untrained adolescents during a 12-week training period, a DNLP program can be used to elicit similar and possible superior maximal strength and flexibility gains compared with an NP multiset training model.

Intensity classification accuracy of accelerometer-measured physical activities in Chinese children and youth

PURPOSE

Many ActiGraph accelerometer cutoff points and equations have been developed to classify children and youth's physical activity (PA) into different intensity levels. Using a sample from the Chinese City Children and Youth Physical Activity Study, this study was to develop new ActiGraph cutoff points for moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) for Chinese children and youth and to compare the classification accuracy to that of a set of existing cutoff points.

METHOD

A total of 367 Chinese children and youth (179 boys, 188 girls, ages 9-17 years old) had their resting metabolic rate measured and completed six 5-min treadmill walking/running tests (tested at different speeds: 3 km x h(-1), 4 km x h(-1), 5 km x h(-1), 6 km x h(-1), 7 km x h(-1), and 8 km x h(-1)), one unit of the 3rd broadcast gymnastics (Version 3, Xi-Wang-Feng-Fan and Wu-Dong-Qing-Chun), and 2 sets of table tennis exercises (continuous attack and multiple balls). Participants wore 1 ActiGraph GT3X accelerometer on their right hip during each test, and their oxygen consumption and heart rate (HR) were measured using Cosmed K4b2 and Polar HR transmitter. The participants were randomly divided into a calibration group (n = 331, 90%) and a cross-validation group (n = 36, 10%). Using the receiver-operating characteristic curve, the data from the calibration group were used to determine the cutoff points for MVPA and VPA. Using the data from the cross-validation group, classification accuracy of different cutoff points was evaluated through kappa statistics, sensitivity, and specificity.

RESULTS

A set of new cutoff points of counts per minute (CPM) was generated using the calibration data, and these cutoff points were proven to be more accurate compared with those developed in previous studies.

CONCLUSION

When using ActiGraph accelerometers to measure the Chinese children and youth's PA, we recommended using the cutoff points of CPM > or = 2,800 to define MVPA and CPM > or = 4,000 for VPA.

Influence of muscle fitness test performance on metabolic risk factors among adolescent girls

BACKGROUND

The purpose of this study was to examine the association between muscular fitness (MF), assessed by 2 components of Fitnessgram test battery, the Curl-Up and Push-Ups tests and the metabolic risk score among adolescent girls.

METHODS

A total of 229 girls (aged 12-15 years old) comprised the sample of this study. Anthropometric data (height, body mass, waist circumference) were collected. Body mass index (BMI) was also calculated. Muscular strength was assessed taking into account the tests that comprised the FITNESSGRAM test battery, i.e. the curl-up and the push-up. Participants were then categorized in one of 3 categories according the number of tests in which they accomplished the scores that allow them to be classified in health or above health zone. The blood pressure [BP], fasting total cholesterol [TC], low density lipoprotein-cholesterol [LDL-C], high density lipoprotein-cholesterol [HDL-C], triglycerides [TG], glucose, and a metabolic risk score (MRS) were also examined. Physical Activity Index (PAI) was obtained by questionnaire.

RESULTS

Higher compliance with health-zone criteria (good in the 2 tests), adjusted for age and maturation, were positive and significantly (p </= 0.05) associated with height (r = 0.19) and PAI (r = 0.21), while a significant but negative association was found for BMI (r = -0.12); WC (r = -0.19); TC (r = -0.16); TG (r = -0.16); LDL (r = -0.16) and MRS (r = -0.16). Logistic regression showed that who were assigned to MF fittest group were less likely (OR = 0.27; p = 0.003) to be classified overweight/obese and less likely (OR = 0.26; p = 0.03) to be classified as having MRS. This last association was also found for those whom only performed 1 test under the health zone (OR = 0.23; p = 0.02).

CONCLUSIONS

Our data showed that low strength test performance was associated with increased risk for obesity and metabolic risk in adolescent girls even after adjustment for age and maturation.

Exercise adherence and intervention effects of two school-based resistance training programs for adolescents

OBJECTIVE

The aim of this study was to evaluate the efficacy and feasibility of two school-based RT programs to improve muscular fitness and body composition in adolescents.

METHODS

The study was conducted in Australia from July 2008 to June 2009. Participants [n=108, mean age (SD)=15.0 (0.7) years] were randomized to free weights (n=37) or elastic tubing (n=41) RT groups and a control group was recruited (n=30). Participants in the RT groups completed 2 sets of 10-12 repetitions on 10 exercises for 8 weeks. Waist circumference, body composition (bioelectrical impedance analysis) and muscular strength (bench press and leg press) were assessed at baseline and posttest.

RESULTS

Boys (p<0.001) and girls (p<0.01) in both RT groups improved their body composition over the study period. Boys in both RT groups significantly improved both upper and lower body strength and their improvements were significantly greater than changes observed in the control group. Girls in the free weights groups achieved larger improvements in lower body strength compared to the control group (p<0.05).

CONCLUSIONS

Free weights and elastic tubing RT are feasible and effective strategies for improving aspects of health-related fitness in adolescents.

Resistance training among young athletes: safety, efficacy and injury prevention effects

A literature review was employed to evaluate the current epidemiology of injury related to the safety and efficacy of youth resistance training. Several case study reports and retrospective questionnaires regarding resistance exercise and the competitive sports of weightlifting and powerlifting reveal that injuries have occurred in young lifters, although a majority can be classified as accidental. Lack of qualified instruction that underlies poor exercise technique and inappropriate training loads could explain, at least partly, some of the reported injuries. Current research indicates that resistance training can be a safe, effective and worthwhile activity for children and adolescents provided that qualified professionals supervise all training sessions and provide age-appropriate instruction on proper lifting procedures and safe training guidelines. Regular participation in a multifaceted resistance training programme that begins during the preseason and includes instruction on movement biomechanics may reduce the risk of sports-related injuries in young athletes. Strategies for enhancing the safety of youth resistance training are discussed.

Canadian Society for Exercise Physiology position paper: resistance training in children and adolescents

Many position stands and review papers have refuted the myths associated with resistance training (RT) in children and adolescents. With proper training methods, RT for children and adolescents can be relatively safe and improve overall health. The objective of this position paper and review is to highlight research and provide recommendations in aspects of RT that have not been extensively reported in the pediatric literature. In addition to the well-documented increases in muscular strength and endurance, RT has been used to improve function in pediatric patients with cystic fibrosis and cerebral palsy, as well as pediatric burn victims. Increases in children's muscular strength have been attributed primarily to neurological adaptations due to the disproportionately higher increase in muscle strength than in muscle size. Although most studies using anthropometric measures have not shown significant muscle hypertrophy in children, more sensitive measures such as magnetic resonance imaging and ultrasound have suggested hypertrophy may occur. There is no minimum age for RT for children. However, the training and instruction must be appropriate for children and adolescents, involving a proper warm-up, cool-down, and appropriate choice of exercises. It is recommended that low- to moderate-intensity resistance exercise should be done 2-3 times/week on non-consecutive days, with 1-2 sets initially, progressing to 4 sets of 8-15 repetitions for 8-12 exercises. These exercises can include more advanced movements such as Olympic-style lifting, plyometrics, and balance training, which can enhance strength, power, co-ordination, and balance. However, specific guidelines for these more advanced techniques need to be established for youth. In conclusion, an RT program that is within a child's or adolescent's capacity and involves gradual progression under qualified instruction and supervision with appropriately sized equipment can involve more advanced or intense RT exercises, which can lead to functional (i.e., muscular strength, endurance, power, balance, and co-ordination) and health benefits.

Physical Activity: The Epidemic of Obesity and Overweight Among Youth: Trends, Consequences, and Interventions

Childhood and adolescent overweight and obesity are an epidemic problem in the United States. Studies show that approximately one third of youth are overweight or obese, representing a tripling since the 1960s and 1970s. The average male and female adult in the United States has gained 25 lbs and 24 lbs, respectively, since 1962. The body mass index of the average adult has increased from 25 to 28. Among youth, the average body mass index has increased from 21.3 to 24.1 since 1963. This increase in bodyweight among adults and youth is partially due to the decreased levels of physical activity. The economic and health consequences of this epidemic are enormous. Type 2 diabetes mellitus, a disease that was rare among youth 20 to 30 years ago, now represents as many as 45% of all cases of diabetes among youth. Cardiovascular risk factors are worsened in overweight and obese youth, and early evidence of atherosclerosis manifested by endothelial dysfunction and increased coronary artery calcium is present in a high percentage of overweight youth. Numerous psychosocial problems also are increased among overweight and obese youth. However, there are numerous examples in the scientific literature of successful approaches to the prevention and management of overweight and obesity in youth. This article summarizes statistics concerning the prevalence of overweight, obesity, and physical inactivity among youth; discusses the numerous physical and psychosocial consequences of overweight and obesity among youth; and presents information regarding interventions that have been demonstrated to be effective in preventing childhood and adolescent overweight and obesity.