Dynapenia: it's not just for grown-ups anymore

Resistance training effects on pubertal children with a risk of developing pediatric dynapenia

PURPOSE

Many modern-day children are at risk of pediatric dynapenia (muscle weakness). We examined the effects of a 12-week resistance training (RT) program on neuromuscular function and body composition parameters in pubertal children with a risk of dynapenia.

METHODS

Twelve children (13.4 ± 0.9 y) with dynapenia performed a progressive RT program consisting of knee extension and flexion, bench press, abdominal crunch, back extension, lateral pull-down, elbow flexion, and upright row (1-2 sets of 10-15 repetitions/exercise) twice/week for 12 weeks. Outcome measures included one-repetition maximum (1-RM) strength, maximal voluntary isometric contraction (MVIC) torque, rate of torque development (RTD), electromyographic (EMG) activity, muscle thickness (MT), muscle quality (MQ) assessed by echo intensity (MQEI) of the knee extensors and specific tension of MVIC torque to thigh fat-free mass (MQST), and total and regional body and bone composition assessed by dual-energy X-ray absorptiometry. Changes in the measures before and after the 12-week RT and associations among the measures were analyzed by linear mixed models.

RESULTS

Significant (p < 0.05) increases in 1-RM (63.9 ± 4.5%), MVIC torque (16.3 ± 17.8%), MT (18.8 ± 5.5%) and MQ (MQEI: -25.9 ± 15.2%; MQST: 15.1 ± 18.8%;) were evident from pre- to post-training. Total fat-free mass (FFM) increased by 2.3 ± 3.2% from baseline (p = 0.01), but no changes (p > 0.05) in the other measures were observed. Significant (p < 0.05) associations between the changes in 1-RM and/or MVIC torque and the changes in quadriceps MT, MQEI, MQST and total body FFM were evident.

CONCLUSIONS

The 12-week RT was effective for improving neuromuscular and body composition parameters, and thereby reversed the risk of pediatric dynapenia.

Are accelerometer-measured sitting and physical activity times associated with muscle mass and strength in healthy young adults in the UAE?

Background

A high prevalence of obesity, sedentary behavior, and physical inactivity could affect muscle mass and strength in young adults in the United Arab Emirates (UAE). Therefore, we investigated the association of sex, body mass index (BMI), and accelerometer-measured sitting and physical activity (PA) times with skeletal muscle mass index (SMI), hand grip, and thigh muscle strength in healthy young adults in the UAE.

Methods

In this cross-sectional study, 156 healthy young adults (age 21.68 ± 3.01 years, BMI 25.40 ± 4.79 kg/m2, 52.6 % women) were included. BMI and muscle mass were recorded using a bioelectrical impedance analyzer. Maximum hand grip strength and thigh muscle torque were assessed using the Jamar-smart hand-dynamometer and Biodex System-4-Pro, respectively. Participants wore a triaxial Fibion accelerometer on their anterior thigh for >10 h per day for 4-7 days to measure their sitting and PA times. Multiple linear regression analyses were used.

Results

Participants spent most of their time sitting (11.37 ± 1.10 h), followed by standing (2.92 ± 0.86 h), walking (1.58 ± 0.55 h), and vigorous intensity PA (4.79 ± 5.85 min) per 16-h day. Sex (p < 0.001) and BMI (p < 0.001) were negatively associated with all muscle mass and strength variables. Men had more muscle mass and strength than women. As BMI increased, muscle mass and muscle strength decreased. Accelerometer-measured sitting and walking times were negatively associated with concentric hamstrings (p = 0.044) and quadriceps torques (p = 0.031), respectively.

Conclusion

Sex, BMI, and accelerometer-measured sitting and walking times were associated with muscle mass and/or muscle strength in healthy young adults. Women and those with a high BMI need interventions to improve their muscle mass and strength. The paradox regarding the association of PA with muscle mass and strength in younger adults may be due to possible influences from other factors (e.g., resistance training, dietary intakes, etc.) superseding that of accelerometer-measured PA.

May the Force Be with Youth: Foundational Strength for Lifelong Development

ABSTRACT

Today's youth are weaker than previous generations, and measurable reductions in physical fitness are beginning to emerge. Without targeted initiatives that recognize the foundational importance of resistance training, weaker children and adolescents may be more likely to experience the inevitable consequences of neuromuscular dysfunction and less likely to experience the pleiotropic benefits of exercise and sport. Early exposure to strength-building activities is needed to prepare today's youth for ongoing participation in varied physical activities throughout this developmental phase of life. The novel iceberg of physical development is a metaphoric image that illustrates the sequential and cumulative influence of muscular strength on motor skills and physical abilities. Efforts to enhance the physical capacity of youth should include resistive skills that improve basic movement patterns and enhance motoric competence. A shift in our conceptual thinking about youth resistance training is needed to alter the current trajectory toward physical inactivity and related comorbidities.

Associations between physical activity, physical fitness, and body composition in adults living in Germany: A cross-sectional study

BACKGROUND & AIMS

Body composition (BC) changes with age and is associated with morbidity and mortality. A physically active lifestyle influences BC and represents an important predictor of successful aging. To emphasize this, the World Health Organization established activity recommendations for all age groups. We describe BC during adulthood using a cross-sectional sample from a German community and investigate the associations between physical activity (PA), physical fitness (PF), and BC.

METHODS

Data from 329 men and women aged 35 to 86 years were analyzed. PA was measured by questionnaire and classified into sport activity and habitual activity. PF was measured through physical performance tests and BC by bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations between PA, PF, and BC were analyzed using linear regression models.

RESULTS

For both sexes, strength was positively associated with FFMI (♂: ß = 0.313; ♀: ß = 0.213) and phase angle (♂: ß = 0.357; ♀: ß = 0.409). For FMI, a significant negative association with strength was found only in women (ß = -0.189). Cardiorespiratory fitness showed a negative association with FMI (ß = -0.312) and FFMI (ß = -0.201) for men, while in women a positive association was found for FFMI (ß = 0.186). For coordination, a significant association with FMI was observed only in women (ß = -0.190). Regarding PA only one significant relationship between sport activity and FMI among women (ß = -0.170) was found.

CONCLUSIONS

In our sample, PF was closer related to BC than PA. Strength and cardiorespiratory fitness were the strongest predictors for BC. This supports the World Health Organization's activity recommendations to include both resistance and endurance training in the weekly sports program to maintain a healthy BC.

Fitness Changes in Adolescent Girls Following In-School Combined Aerobic and Resistance Exercise: Interaction With Birthweight

PURPOSE

To assess the efficacy of a supervised in-school combined resistance and aerobic training program in adolescent girls and investigate whether responses differ according to birthweight.

METHODS

Participants (girls aged 13-17 y) were randomized either to an intervention replacing physical education (PE) classes with 2 × 60-minute training sessions per week (n = 58) or to a control group that continued to attend 2 × 60 minutes per week of curriculum PE (n = 41). We measured muscular fitness (handgrip, standing long jump, and sit-ups), cardiorespiratory fitness (20-m shuttle run), skinfolds, and lean body mass preintervention and postintervention and determined effect size (Hedge's g) differences between changes in these measures. We also compared changes within lower (<3000 g) and normal birthweight intervention and PE control subgroups.

RESULTS

The intervention group showed greater improvements in all the fitness measures and lean body mass (g = 0.22-0.48) and lower skinfold increases (g = 0.41) than PE controls. Within the intervention group, improvements in all fitness measures were larger in lower birthweight (g = 0.53-0.94) than in normal birthweight girls (g = 0.02-0.39).

CONCLUSION

Replacing curriculum PE with supervised training improved muscular and cardiorespiratory fitness and body composition outcomes in adolescent females. Our findings suggest an enhanced adaptive response to training in participants with lower birthweight which warrants further investigation.

Integrative Neuromuscular Training in Adolescents and Children Treated for Cancer (INTERACT): Study Protocol for a Multicenter, Two-Arm Parallel-Group Randomized Controlled Superiority Trial

BACKGROUND

Improved survival rates for children and adolescents diagnosed with cancer call for novel strategies for reducing short- and long-term treatment-related side effects. These include the physical and metabolic sequelae that are exacerbated by sedentary behavior and treatment-induced toxicities. We aim to investigate the effect of an integrative neuromuscular training intervention during the first 6 months of anti-cancer treatment primarily on muscle strength, and secondarily on exercise capacity, physical function, markers of metabolic syndrome, dysmetabolism, and health-related quality of life during and after ended treatment.

METHODS

One hundred and twenty-seven children and adolescents, newly diagnosed with malignant and benign neoplasia, aged 6-17 years, and treated with chemotherapy or radiation will be randomized to either the intervention or the control arm of the study. The intervention group will, in addition to usual care, be offered a combination of 6 months of supervised physical exercise (integrative neuromuscular training) and home-based exercise. The active control group will, in addition to usual care, receive information along an unsupervised written home-based training program. All participants, including parents, will receive information about the importance of physical exercise during the course of cancer treatment, at the start of treatment, and in 5 monthly sessions. The primary outcome is measured in terms of isometric quadriceps muscle strength. Secondary outcomes include muscle strength and endurance, markers of metabolic syndrome and dysmetabolism, exercise capacity, physical function and activity, days of hospitalization, and health-related quality of life. Assessment will be conducted at treatment initiation (baseline), at 3 and 6 months after inclusion, and 1 month and 1 year after ended treatment. The primary endpoint for lower-body muscle strength is at 6 months after treatment initiation. The effects of the intervention will be evaluated through a constrained linear mixed model.

DISCUSSION

This national randomized controlled study has the potential to provide new knowledge concerning the short- and long-term effects of a novel, inclusive approach for youth exercise programming (integrative neuromuscular exercise) in children and adolescents during anti-cancer treatment. Using a pragmatic, low-cost, and time-efficient training design, this intervention can be easily adapted to both hospital and home settings.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NCT04706676), first released January 5, 2021.

Physical Illiteracy and Obesity Barrier: How Physical Education Can Overpass Potential Adverse Effects? A Narrative Review

Environments lacking in stimuli together with ineffective physical education programs can lead to motor illiteracy, causing several adverse effects that could be worsened by unhealthy weight conditions (e.g., obesity). Obesity can be seen as an actual barrier for children and adolescents, especially for affective, behavioral, physical, and cognitive domains. In this context, condensing what the literature proposes could be useful in order to improve the understanding of the best intervention strategies (i.e., proper physical education programs) to manage the adverse effects of motor illiteracy in relation to the obesity barrier. The purpose of this narrative review is to improve the understanding on how physical education programs can counteract the adverse effects of physical illiteracy and obesity barrier across childhood and adolescence. Proper physical education programs should develop motor competence by fostering an individual’s awareness, self-perception, autonomous motivation, and muscular fitness on a realistic scenario (functional task difficulty related to his/her possibilities) in the attempt to counteract the adverse effects of the obesity barrier. Such programs should be designed without overlooking a proper multi teaching style approach.

The effects of daily physical activity intervention on physical fitness in preschool children

The study aimed to determine the effects of 6 months daily physical activity on physical fitness in preschool children. A total of 72 children (36 boys) and 92 children (47 boys) composed the experimental (EG) and control group (CG), respectively. We used the PREFIT battery access physical fitness. In EG, participants had 45 minutes of organized physical activity 5 days per week. The CG continued their usual routine with 30 minutes of structured physical activity two times per week. The EG improved the mean performance of grip strength (η p2=0.08) and sit-ups in the 30s ( p2=0.16) to a significantly greater extent as compared to the CG. In boys, the improvements of mean performance of handgrip strength (η p2=0.13), 4x10m shuttle run η p2=0.09), standing long jump (η p2=0.05), sit-ups in 30s (η p2=0.17) were significantly greater in EG than in the CG. However, girls in EG only had significant improvements  in the sit-ups in the 30 s test compared to CG (η p2=0.14). Overall, our study shows that after 6 months of daily exercise programme, preschool children improved muscular strength compared to those peers allocated in the control group. No significant differences between groups were found in the remaining fitness components analysed.

Associations of fitness, motor competence, and adiposity with the indicators of physical activity intensity during different physical activities in children

We investigated the associations of peak oxygen uptake (V̇O2peak), ventilatory threshold (VT), muscle strength, motor competence (MC), and adiposity with the indicators of PA intensity during different physical activities used to create absolute PA intensity cut-offs among 35 children 7-11-years-of-age. V̇O2peak was defined as the highest V̇O2 achieved in the maximal cardiopulmonary exercise test (CPET) on a cycle ergometer, self-paced running, or running on a treadmill at 8 km/h. VT was defined from the CPET data. Peak isometric knee extensor and flexor strength was assessed by a dynamometer, MC by the Körperkoordination test für Kinder tests, and body composition by the bioelectrical impedance analysis. PA intensity was assessed using V̇O2 as a % of V̇O2reserve or V̇O2 at VT, mean amplitude deviation (MAD) measured by accelerometry, metabolic equivalent of task (MET), and muscle activity measured by textile electromyography during walking or running on a treadmill at 4, 6, and 8 km/h, playing hopscotch, walking up and down the stairs, self-paced walking, and self-paced running. Children with lower V̇O2peak, V̇O2 at VT, and MC operated at higher intensity level during given physical task than their peers with higher fitness and MC when PA intensity was expressed using relative PA intensity using V̇O2 as a % of V̇O2reserve or V̇O2 at VT (p < 0.05). MAD and METs during different tasks were not able to discriminate PA intensity between children with varying levels of physical fitness or MC. Traditionally used absolute measures of PA intensity based on accelerometry or MET underestimated PA intensity in children with lower V̇O2peak, V̇O2 at VT, and MC.

The SIMAC study: A randomized controlled trial to compare the effects of resistance training and aerobic training on the fitness and body composition of Colombian adolescents

The aim of this study was to evaluate the impact on muscle strength, aerobic fitness and body composition, of replacing the physical education (PE) class of Colombian adolescents with resistance or aerobic training. 120 tanner stage 3 adolescents attending a state school were randomized to resistance training, aerobic training, or a control group who continued to attend a weekly 2- hour PE class for 16 weeks. The resistance training and aerobic training groups participated in twice weekly supervised after-school exercise sessions of < 1 hour instead of their PE class. Sum of skinfolds, lean body mass (bioelectrical impedance analysis), muscular strength (6 repetition maximum (RM)) bench press, lateral pulldown and leg press) and estimated cardiorespiratory fitness (multistage 20 meter shuttle run) were assessed at pre and post intervention. Complete data were available for n = 40 of the resistance training group, n = 40 of the aerobic training group and n = 30 PE (controls). Resistance training attenuated increases in sum of skinfolds compared with controls (d = 0.27, [0.09-0.36]). We found no significant effect on lean body mass. Resistance training produced a positive effect on muscle strength compared with both controls (d = 0.66 [.49-.86]) and aerobic training (d = 0.55[0.28-0.67]). There was a positive effect of resistance training on cardiorespiratory fitness compared with controls (d = 0.04 [-0.10-0.12]) but not compared with aerobic training (d = 0.24 [0.10-0.36]). Replacing a 2-hour PE class with two 1 hour resistance training sessions attenuated gains in subcutaneous adiposity, and enhanced muscle strength and aerobic fitness development in Colombian youth, based on a median attendance of approximately 1 session a week. Further research to assess whether adequate stimuli for the development of muscular fitness exists within current physical education provision is warranted.

Making a Strong Case for Prioritizing Muscular Fitness in Youth Physical Activity Guidelines

Although evidence indicates that muscular fitness is foundational for ongoing participation in active play, exercise and sport, current national and international youth physical activity guidelines underplay the critical importance of strength-building activities during this developmental phase of life. In view of troubling trends in muscular fitness in today's youth, specific recommendations to address neuromuscular deficiencies are required. An understanding of the multidimensional development of youth physical inactivity and the importance of muscular fitness are needed to have the most significant impact on youth physical activity at the population level. The mounting evidence of the detrimental effects of physical inactivity on youth warrant a review of existing physical activity recommendations and guidelines. The proposed pediatric activity pyramid recognizes the shared importance of strength, skill, and aerobic activities required for the successful implementation of sustainable youth physical activity interventions.

An Update on Secular Trends in Physical Fitness of Children and Adolescents from 1972 to 2015: A Systematic Review

BACKGROUND

There is evidence that physical fitness of children and adolescents (particularly cardiorespiratory endurance) has declined globally over the past decades. Ever since the first reports on negative trends in physical fitness, efforts have been undertaken by for instance the World Health Organization (WHO) to promote physical activity and fitness in children and adolescents. Therefore, it is timely to re-analyze the literature to examine whether previous reports on secular declines in physical fitness are still detectable or whether they need to be updated.

OBJECTIVES

The objective of this systematic review is to provide an 'update' on secular trends in selected components of physical fitness (i.e., cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed) in children and adolescents aged 6-18 years.

DATA SOURCES

A systematic computerized literature search was conducted in the electronic databases PubMed and Web of Science to locate studies that explicitly reported secular trends in physical fitness of children and adolescents.

STUDY ELIGIBILITY CRITERIA

Studies were included in this systematic review if they examined secular trends between at least two time points across a minimum of 5 years. In addition, they had to document secular trends in any measure of cardiorespiratory endurance, relative muscle strength, proxies of muscle power or speed in apparently healthy children and adolescents aged 6-18 years.

STUDY APPRAISAL AND SYNTHESIS METHODS

The included studies were coded for the following criteria: nation, physical fitness component (cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed), chronological age, sex (boys vs. girls), and year of assessment. Scores were standardized (i.e., converted to z scores) with sample-weighted means and standard deviations, pooled across sex and year of assessment within cells defined by study, test, and children's age.

RESULTS

The original search identified 524 hits. In the end, 22 studies met the inclusion criteria for review. The observation period was between 1972 and 2015. Fifteen of the 22 studies used tests for cardiorespiratory endurance, eight for relative muscle strength, eleven for proxies of muscle power, and eight for speed. Measures of cardiorespiratory endurance exhibited a large initial increase and an equally large subsequent decrease, but the decrease appears to have reached a floor for all children between 2010 and 2015. Measures of relative muscle strength showed a general trend towards a small increase. Measures of proxies of muscle power indicated an overall small negative quadratic trend. For measures of speed, a small-to-medium increase was observed in recent years.

LIMITATIONS

Biological maturity was not considered in the analysis because biological maturity was not reported in most included studies.

CONCLUSIONS

Negative secular trends were particularly found for cardiorespiratory endurance between 1986 and 2010-12, irrespective of sex. Relative muscle strength and speed showed small increases while proxies of muscle power declined. Although the negative trend in cardiorespiratory endurance appears to have reached a floor in recent years, because of its association with markers of health, we recommend further initiatives in PA and fitness promotion for children and adolescents. More specifically, public health efforts should focus on exercise that increases cardiorespiratory endurance to prevent adverse health effects (i.e., overweight and obesity) and muscle strength to lay a foundation for motor skill learning.

Comparing the torque- and power-velocity relationships between children and adolescents during isokinetic leg extension muscle actions

The purpose of this study was to use polynomial regression analyses to examine the torque- and power-velocity relationships and calculate and compare the vertices of these nonlinear models, and how they relate to measurements of muscle size and maximal strength, between male and female children and adolescents during maximal isokinetic leg extension muscle actions. Sixteen children (n = 8 males, n = 8 females) and 22 adolescents (n = 11 males, n = 11 females) participated in this study. Measurements of growth included age, maturity offset, height, body mass, fat-free mass, and quadriceps femoris muscle cross-sectional area (CSA). Participants completed maximal voluntary isometric contractions (MVICs) of the leg extensors and maximal voluntary isokinetic leg extensions at 60, 120, 180, 240, and 300°·s^-1. Variables calculated during all leg extension muscle actions included peak torque (PT, Nm) and mean power (MP, W). Polynomial regression analyses determined the model of best fit for the PT- and MP-velocity relationships. For each participant, the vertex from the PT- and MP-velocity quadratic models were quantified as the predicted maximum velocity of last measurable torque (V_PT) and the predicted velocity of maximum mean power (V_MP), respectively. Measurements of growth, PT and MP at all velocities, V_PT, and V_MP were greater in the adolescents than children. When normalized to CSA, V_PT and V_MP remained greater for adolescents than children, and exhibited low to very high relationships with measurements of growth. When normalized to MVIC strength, V_PT and V_MP were no longer different between children and adolescents and exhibited negligible to low relationships with measurements of growth. The results of the present study suggest that the ability to produce torque and power at high velocities may be more dependent on muscle strength than muscle size, which suggests that mechanisms other than muscular hypertrophy affect torque and power production at high velocities in young males and females.

Integrated Strength and Fundamental Movement Skill Training in Children: A Pilot Study

Competence in fundamental movement skills is essential to enable children to be physically active. We investigated the effect of an integrated fundamental movement skill with a strength training intervention on children’s fundamental movement skills. Seventy-two (53% female) 10- to 11-year-old children from three primary schools assented to take part in this study (87% compliance). Schools were randomly allocated to a control (no intervention; n = 21), fundamental movement skill (FMS) (n = 18) or FMS and strength (FMS⁺; n = 20) group. Interventions were delivered twice weekly for four weeks, in addition to normal physical education. FMS competence was measured through the Canadian agility and movement skills assessment (CAMSA) (product-process) and through countermovement jump (CMJ) and 40-m sprint tests (product). Improvements were observed in the CAMSA in both FMS (4.6, 95% confidence intervals 2.9 to 6.4 Arbitrary Units (AUs), second-generation p-value (p_δ) = 0.03) and FMS⁺ (3.9, 2.1 to 5.3 AU, p_δ = 0.28) with no difference beyond our minimum threshold of 3 AU observed between these intervention groups (p_δ = 1). Clear improvements in CMJ were observed in FMS⁺ relative to the control (25, 18 to 32%, p_δ = 0) and FMS groups (15, 6.1 to 24%, p_δ = 0). These preliminary data suggest combined FMS and strength training warrants further investigation as a tool to develop fundamental movement skills in children.

A 47-Year Comparison of Lower Body Muscular Power in Spanish Boys: A Short Report

Much of the evidence examining temporal trends in fitness among youth has found a decrease in measures of muscular strength and muscular power over recent decades. The aim of this study was to examine trends in lower body muscular power in Spanish boys over 47 years. In 1969 140 boys (10-11 years; body mass index = 19.24, SD = 2.91 kg/m²) and in 2016, 113 boys (10-11 years; body mass index = 19.20, SD = 3.15 kg/m²) were recruited. Lower body power was assessed using the vertical jump (VJ) and standing long jump (SLJ) tests. Significant differences and a large effect size were shown between groups in the SLJ (p = 0.001; d = 0.94) and the VJ (p = 0.001; d = 0.66). SLJ data in 1969 were higher (1.52 m, SD = 0.19) when compared to the 2016 data (1.34 m, SD = 0.18). The VJ performance of the 1969 sample was also higher (25.95 cm; SD = 6.58) than the 2016 sample (21.56 cm; SD = 4.72). SLJ and VJ performance of the 2016 group decreased 11.8% and 16.9%, respectively. There were no significant differences between groups in body mass index. The results indicate a secular decline in lower body muscular power in 10-11-year-old Spanish boys with no significant changes in body mass index over the 47-year study period.

Growing up strong: The importance of physical, mental, and emotional strength during childhood and adolescence with focus on dietary factors

Childhood and adolescence are critical time periods for growth and development. Given the current physical and psychological health concerns affecting United States youth, an emerging area of interest exists supporting the importance of physical and psychological aspects of strength for health, resilience, and well-being through these life stages. This synopsis highlights the key concepts that were presented within the 2018 Strength Summit conference, entitled The Role of Strength in Optimal Health and Well-being. During the conference, strength was broadly defined as the ability to successfully respond to a challenge. Although much of the current research focuses on strength from a muscle function and performance perspective, mental and emotional strength are also important components of overall health and well-being, especially in children and adolescents. This paper provides a brief overview of the clinical and/or research-based strength outcomes, summarizes the relationship between strength and health, and discusses evidence-based dietary factors that promote strength in children and adolescents. Novelty Building physical, mental, and emotional strength during childhood and adolescence lays the foundation for health and well-being. Emerging evidence indicate positive associations between diet quality and strength in children and adolescents. Promising areas include the promotion of family-based meals, with focus on breakfast, for improved strength in United States youth.

Nine Months of a Structured Multisport Program Improve Physical Fitness in Preschool Children: A Quasi-Experimental Study

Research in preschool children that investigates the impact of different exercise interventions on physical fitness is limited. This pre-post study was aimed at determining if participation in a nine-month structured multisport program (MSG; n = 38) could enhance physical fitness components compared to a formal exercise program (control group (CG); n = 36) among preschool children. Physical fitness was assessed using standardized tests (the standing long jump, sit and reach, 20 m sprint, sit-ups for 30 s, bent-arm hang, medicine ball throw (MBT), grip strength, 4 × 10 m shuttle run, and 20 m shuttle run tests). The structured multisport program involved fundamental/gross and fine motor skills and ball game-based exercises twice a week. The control group was free of any programmed exercise except for the obligatory program in kindergartens. A mixed ANOVA demonstrated significant group-by-time interaction effects for the 4 × 10 m shuttle run, standing long jump, sit-ups, bent-arm hang, grip strength, and sit and reach tests (p < 0.05). There was no significant group-by-time interaction effect for the 20 m sprint test (p = 0.794) or for the 20 m shuttle run test (p = 0.549). Moreover, the MSG and CG performance in the MBT and 20 m shuttle run tests improved to a similar extent from pre- to post-test. Our results indicate that compared to the formal plan, the structured multisport program led to a sustained improvement in physical fitness in healthy 5-to-6-year old children.

Construct validity of the PERF-FIT, a test of motor skill-related fitness for children in low resource areas

BACKGROUND

Given the relationship between physical fitness and motor performance a test battery was developed that measures both components combined.

AIM

Following the development of the Performance and Fitness (PERF-FIT) battery, this study investigated the construct validity with the ultimate aim of identifying attributes that discriminate between different levels of motor abilities and anaerobic or musculoskeletal fitness.

METHODS

In this cross-sectional study, 34 children with developmental coordination disorder (DCD) and 34 matched typically developing children participated (7-10 years). The PERF-FIT was used to examine known group validity. The PERF-FIT items were also compared to test items of well-known standardized tests to examine concurrent validity.

RESULTS

Concurrent validity was found to be of the expected low to moderate magnitude. Children with DCD were consistently found to have lower levels of motor skill-related fitness compared to typically developing children.

CONCLUSION AND IMPLICATIONS

The PERF-FIT seems to be a valid test to measure movement skills, musculoskeletal fitness and agility in children between the ages of 7 and 10 years in low resourced communities. The test seems to discriminate between gross motor skills, and agility and power in children with and without DCD.

Relative handgrip strength, nutritional status and abdominal obesity in Chilean adolescents

Handgrip strength (HGS) is a well-established indicator of muscle strength and can help to identify risk of sarcopenic obesity in children. This study explores the relationship between adiposity and muscular strength in healthy Chilean adolescents. Adolescents (n = 491) aged 10–17 were selected from five schools in Santiago, Chile. HGS was determined by dynamometry. Anthropometry (weight, height, waist and mid arm circumference), physical activity and socioeconomic status were also measured. Relative HGS (RHGS) was calculated by dividing maximum HGS of the dominant hand by body-mass index (BMI) and low RHGS was categorized as <25^th percentile by sex. Logistic regression was used to determine the relationship between two markers of adiposity (abdominal obesity category by waist circumference and nutritional status measured by BMI category) and low RHGS, adjusting for possible confounding variables. Participants were on average 13.6y (2.4), 32.8% were overweight or obese and 37.5% were at risk of or had abdominal obesity. RHGS was 1.25 kg/kg/m² overall, with a significant difference by sex (1.51 for boys versus 1.14 for girls). In adjusted analyses, boys and girls with risk of abdominal obesity, had 3.3 (1.6–6.6) and 4.1 (1.8–9.3) increased odds of low RHGS, respectively, compared to boys and girls with normal waist circumference. Those with abdominal obesity compared to normal WC, had 8.5 (3.4–21.4) and 6.5 (2.0–21.3) increased odds of low RHGS for boys and girls, respectively. We observed similar associations for BMI category. In our sample of healthy adolescents, higher adiposity related to greater odds of low muscle strength measured by dynamometry. Considering the demographic shift from a young to an aging population in many countries, along with the increasing prevalence of obesity beginning in childhood, understanding how adiposity relates to low muscle strength is of growing importance.

Expert's Choice: 2018's Most Exciting Research in the Field of Pediatric Exercise Science

This commentary highlights 23 noteworthy publications from 2018, selected by leading scientists in pediatric exercise science. These publications have been deemed as significant or exciting in the field as they (a) reveal a new mechanism, (b) highlight a new measurement tool, (c) discuss a new concept or interpretation/application of an existing concept, or (d) describe a new therapeutic approach or clinical tool in youth. In some cases, findings in adults are highlighted, as they may have important implications in youth. The selected publications span the field of pediatric exercise science, specifically focusing on: aerobic exercise and training; neuromuscular physiology, exercise, and training; endocrinology and exercise; resistance training; physical activity and bone strength; growth, maturation, and exercise; physical activity and cognition; childhood obesity, physical activity, and exercise; pulmonary physiology or diseases, exercise, and training; immunology and exercise; cardiovascular physiology and disease; and physical activity, inactivity, and health.

Postural control and balance in a cohort of healthy people living in Europe: An observational study

In the past 20 years, posturography has been widely used in the medical field. This observational study aimed to report the values derived from posturography of a wide set of healthy subjects from various European countries using a plantar pressure platform and a standardized method of measurement.A random cluster sampling of 914 healthy subjects aged between 7.0 and 85.99 years, stratified by age, was carried out. To provide percentile values of our cohort, data were processed to obtain 3 curves corresponding to the following percentiles: 25th, 50th, 75th, and the interquartile range. Distance-weighted least squares method was used to represent the percentile on appropriate graphs.In our sample, the balance to improve with age, up to approximately 45 years, but the trend to reverse with older age. The data show that the oscillations on the sagittal plane (y-mean) change with advancing age. Young people had more retro-podalic support than older people; the balance shifted forward in elderly people.As the study included a relatively large quantity of data collected using a standardized protocol, these results could be used as normative values of posturography for similar populations. On the basis of this data, correct diagnostic clues will be available to clinicians and professionals in the field. However, further studies are needed to confirm our findings.

Grip Strength Moderates the Association between Anthropometric and Body Composition Indicators and Liver Fat in Youth with an Excess of Adiposity

Paediatric non-alcoholic fatty liver disease (NAFLD) is considered the most common early driver of chronic liver disease. The aim of this study was to examine whether grip strength moderates the association between anthropometric and body composition parameters and controlled attenuation parameter (CAP), an indicator of fat deposits in the liver, in children and adolescents with excess of adiposity. A total of 127 adolescents (67% girls) aged between 11 and 17, attending two public schools in Bogotá (Colombia), who had an axiological evaluation of obesity were included in this study. A grip strength test was assessed as an indicator of muscular strength, and cardiorespiratory fitness by maximal oxygen uptake was assessed using the 20 m shuttle-run test. Waist circumference (WC), waist-to-height ratio (WHtR), fat mass, and visceral adipose tissue (VAT) (cm³) were included as anthropometric and body composition measures. CAP was determined with a FibroScan^® 502 Touch device (Echosens, Paris, France). The anthropometric and body composition parameters including WC, WHtR, fat mass, and VAT were positively associated with the CAP (range β = 0.423 to 0.580), slightly reduced after being adjusted for handgrip strength/weight. The Johnson-Neyman technique revealed a significant inverse relationship between WC, WHtR, VAT, and CAP when grip strength normalized by body mass was above but not equal to or below 0.475 (8.1% of the sample), 0.469 (8.9% of the sample), and 0.470 (8.5% of the sample), respectively. In conclusion, grip strength adjusted by body mass, has a moderating effect on the association between anthropometric and body composition parameters (including WC, WHtR, and VAT) and CAP in in children and adolescents with excess of adiposity, suggesting the importance of promoting muscular strength during paediatric population in order to prevent NAFLD.

Profiles of Physical Fitness Risk Behaviours in School Adolescents from the ASSO Project: A Latent Class Analysis

The aim of the present investigation was to describe profiles of adolescents’ fitness level, identify latent classes of fitness-related risk behaviours, and describe their sociodemographic and environmental predictors. In total, 883 adolescents (16.4 ± 1.4 years; 167.3 ± 10.4 cm; 62.8 ± 13.5 kg; 62.2% males) were assessed for personal and lifestyle information and for physical fitness components. Eleven possible fitness determinants and seven predictors were included. Latent class analysis (LCA) was used to determine fitness-related risk behaviours. Logistic regressions predicted class membership and assessed associations with fitness levels and fitness components. Five latent classes were recognised: 1—virtuous, 30.7% of respondents; 2—low physical activity/sport, 18.8%; 3—incorrect alcohol/food habits, 25.8%; 4—health risk/overweight, 15.9%; 5—malaise/diseases, 8.8%. Sex, age, parents’ overweightness/obesity and education, and school type predicted most classes significantly. Compared to class 1, class 2 had higher odds of having all poor fitness components except upper body maximal strength; class 4 had higher risk of low muscular endurance; and class 5 was likely to have lower maximal strength, muscular endurance, and speed/agility. Educating adolescents to reach a sufficient practice of PA/sport could help decreasing the risk of low health-related fitness more than discouraging them from using alcohol, addressing proper food behaviours and habits, and helping them understand their psychophysical malaise symptoms.

Longitudinal association between ideal cardiovascular health status and muscular fitness in adolescents: The LabMed Physical Activity Study

BACKGROUND AND AIMS

Muscular fitness is an emerging predictor for cardiovascular disease mortality. The ideal cardiovascular health metrics has been inversely related to a subsequent cardiometabolic health in adulthood. However, evidence regarding muscular fitness and ideal cardiovascular health in adolescents is scarce. This study aimed to examine the longitudinal association between ideal cardiovascular health index and muscular fitness.

METHODS AND RESULTS

This study cohort consisted of 331 adolescents (183 girls) from the LabMed Physical Activity Study who were followed from 2011 to 2013. Ideal cardiovascular health, as defined by the American Heart Association, was determined as meeting ideal health factors (total cholesterol, blood pressure, and glucose) and behaviors (smoking status, body mass index, physical activity, and diet). Handgrip strength and standing long jump tests assessed muscular fitness and were transformed into standardized values according to age and sex. ANCOVA showed a significant association between the accumulation of ideal cardiovascular health metrics at baseline and muscular fitness indices at follow-up (F_{(4, 322)} = 2.280, p = 0.04). In addition, the higher the number of ideal cardiovascular health metrics accumulated, the higher the likelihood of having a high muscular fitness over a two-year period (p for trend = 0.01), after adjustments for age, sex, pubertal stage and socioeconomic status and muscular fitness at baseline.

CONCLUSION

The ideal cardiovascular health status during adolescence was associated with high muscular fitness levels over a two-year period.

Changes in muscular fitness and its association with blood pressure in adolescents

The aims of this study were to examine the longitudinal association between muscular fitness (MF) and blood pressure (BP) 2 years later, and to determine whether changes in MF over a 2-year period were associated with BP at follow-up, in adolescents. The sample comprised 734 youths (349 girls) aged from 12 to 18 years. MF was assessed with the standing long jump and handgrip tests. Socioeconomic status, pubertal stage, waist circumference, resting BP, and cardiorespiratory fitness were measured according to standard procedures. Regression analyses showed a significant inverse association between MF at baseline and systolic BP (β = - 0.072; p = 0.032) and rate pressure product (β = - 0.124; p < 0.001) at follow-up, after adjustments for age, sex, height, pubertal stage, and socioeconomic status. However, when analyses were further adjusted for waist circumference and cardiorespiratory fitness, these associations did not remain significant. Adolescents with persistently high and increasing MF exhibited the lowest levels of diastolic BP (F_{(3, 721)} = 3.814, p = 0.018) and systolic BP (F_{(3, 721)} = 3.908, p = 0.014) when compared to those with persistent low MF after adjustment for age, sex, height, socioeconomic status, cardiorespiratory fitness, and waist circumference.Conclusion: This study suggests that persistent greater and increasing MF in youth are associated with lower levels of BP across the adolescence. What is Known: • Currently, there is a growing interest on the health benefits of muscular fitness. • Cross-sectional studies have identified an association between muscular fitness and blood pressure in adolescents. What is New: • Changes in muscular fitness during adolescence were associated with systolic and diastolic BP over a 2-year period. • Adolescents with persistently low muscular fitness exhibited the highest levels of diastolic and systolic BP.

Acute Cardiometabolic Responses to a Novel Training Rope Protocol in Children

Faigenbaum, AD, Kang, J, Ratamess, NA, Farrell, A, Golda, S, Stranieri, A, Coe, J, and Bush, JA. Acute cardiometabolic responses to a novel training rope protocol in children. J Strength Cond Res 32(5): 1197-1206, 2018-The purpose of this study was to quantify the acute cardiometabolic responses to a novel training rope (TR) protocol in children. Fifteen boys (10.6 ± 1.4 years) were tested for peak oxygen uptake (V[Combining Dot Above]O2) on a treadmill and subsequently (2-7 days later) performed a progressive 10-minute protocol of 5 TR exercises (EX): EX1: standing side-to-side waves, EX2: seated alternating waves, EX3: standing alternating waves, EX4: jumping jacks, and EX5: double-arm slams. Participants performed 2 sets of each TR exercise for 30 seconds per set with a 30-second rest interval between sets and exercises. A 12.8-m TR (4.1 kg) was used for all trials, and a metronome was used to standardize cadence. Peak values for V[Combining Dot Above]O2 and HR during the treadmill test were 47.4 ± 8.8 ml·kg·min and 195.1 ± 6.6 b·min, respectively. During the TR protocol, mean V[Combining Dot Above]O2 and HR significantly increased (p ≤ 0.05) from set 1 of EX1 (10.3 ± 2.6 ml·kg·min and 103.2 ± 11.6 b·min, respectively) to set 2 of EX5 (30.0 ± 3.9 ml·kg·min and 168.6 ± 11.8 b·min, respectively). Percentage of peak V[Combining Dot Above]O2 and peak HR values attained during the TR protocol ranged from 21.5 to 64.8% and from 52.9 to 86.4%, respectively. These descriptive data indicate that TR exercise can pose a moderate to vigorous cardiometabolic stimulus in children and with proper supervision and instruction may serve as a worthwhile complement to youth fitness programs.

Youth Resistance Training: The Good, the Bad, and the Ugly-The Year That Was 2017

The good news is that a growing body of evidence recognizes resistance training as foundational to long-term physical development. Original research and reviews published in 2017 conclude that early exposure to developmentally appropriate resistance training can improve markers of health, increase muscular fitness, enhance physical literacy, and reduce the risk of injury in young athletes. Although the papers discussed in the commentary add to our understanding of the pleiotropic benefits of youth resistance training, they also raise concerns. As measures of muscular strength and power have been found to track from childhood to adulthood, the bad news is that youth with low levels of muscular fitness tend to become weak adults who are at increased risk for functional limitations and adverse health outcomes. Furthermore, global participation in youth resistance training is falling far short of public health recommendations, and these ugly trends will likely impact the health and well-being of future generations. A change in current attitudes and common practices is urgently needed to educate parents, practitioners, and clinicians about the potential benefits of resistance training for all children and adolescents, not only young athletes.

Prevalence and correlates of resistance training skill competence in adolescents

The aim of this study is to examine the prevalence and correlates of adolescents' resistance training (RT) skill competence. Participants were 548 adolescents (14.1 ± 0.5 years) from 16 schools in New South Wales, Australia. RT skills were assessed using the Resistance Training Skills Battery. Demographics, BMI, muscular fitness, perceived strength, RT self-efficacy, and motivation for RT were also assessed. The proportion demonstrating "competence" and "near competence" in each of the six RT skills were calculated and sex differences explored. Associations between the combined RT skill score and potential correlates were examined using multi-level linear mixed models. Overall, the prevalence of competence was low (range = 3.3% to 27.9%). Females outperformed males on the squat, lunge and overhead press, whereas males performed better on the push-up (p < .05). Significant associations were seen for a number of correlates, which largely differed by sex. Muscular fitness was moderately and positively associated with RT skills among both males (β = 0.34, 95%CIs = 0.23 to 0.46) and females (β = 0.36, 95%CIs = 0.23 to 0.48). Our findings support a link between RT skills and muscular fitness. Other associations were statistically significant but small in magnitude, and should therefore be interpreted cautiously.

Evaluation of Fitness and the Balance Levels of Children with a Diagnosis of Juvenile Idiopathic Arthritis: A Pilot Study

Background: Juvenile idiopathic arthritis is a main cause of physical disability and has high economic costs for society. The purpose of this study was to assess the fitness levels and the postural and balance deficits with a specific test battery. Methods: Fifty-six subjects were enrolled in this study. Thirty-nine healthy subjects were included in the control group and seventeen in the juvenile idiopathic arthritis group. All subjects were evaluated using a posturography system. The fitness level was evaluated with a battery of tests (Abalakov test, sit-up test, hand grip test, backsaver sit and reach, the toe touch test). An unpaired t-test was used to determine differences. Pearson’s correlation coefficient was used to evaluate the correlation between the tests. Results: The battery of tests demonstrated that subjects in the juvenile idiopathic arthritis group have lower fitness levels compared to the control group. The juvenile idiopathic arthritis group showed low postural control with respect to the control group. Pearson analysis of the juvenile idiopathic arthritis group data showed significant correlations between variables. Pearson’s results from the control group data showed a similar trend. Conclusions: The results suggest that the battery of tests used could be an appropriate tool. However, we highlight that these conclusions need to be supported by other studies with a larger population scale.