Factors associated with muscular fitness phenotypes in Australian children: A cross-sectional study

ABSTRACT

To help inform strategies aimed at increasing muscular fitness levels, we examined factors associated with childhood muscular fitness (strength and power) that preceded the recently observed secular decline. Data were available from a nationally representative sample of Australian children aged 7–15 years in 1985 (n = 8469). Muscular fitness measures included strength (right and left grip, shoulder extension and flexion, and leg strength) and power (standing long jump distance). Anthropometric (adiposity, fat-free mass), cardiorespiratory fitness (CRF), flexibility, speed capability, physical activity (individual and parental), dietary quality and intake (fruit, vegetable, protein) and sociodemographic (area-level socioeconomic status (SES), school type) data were available. Statistical analyses included sex-stratified linear regression. Of all examined factors, measures of adiposity, fat-free mass, CRF, flexibility and speed capability were associated with muscular fitness at levels that met Cohen’s threshold for important effects (r-squared = 0.02 to 0.28). These findings highlight the multifactorial relationship between muscular fitness and its determinants. Collectively, these factors were powerful in explaining muscular strength (females: r-squared = 0.32; males: r-squared = 0.41) and muscular power (females: r-squared = 0.36; males: r-squared = 0.42). These findings highlight modifiable and environmental factors that could be targeted to increase childhood muscular fitness.     

A cross-sectional study on the deprivation and sex differences in health-related fitness measures in school children

ABSTRACT

This study aimed to investigate deprivation and sex differences in selected health-relatedfitness measures in 9-12-year-old children. Data were captured on 3,407 children (49.3% boys; aged 10.5 ± 0.6 years). Cardiorespiratory fitness(20 m multistage shuttle run test; 20 m MSRT), muscular strength (handgrip strength) and body mass index (BMI) were measured. Welsh Index of Multiple Deprivation (WIMD) scores were used to make quintile groups. A two-way Analysis of Variance examined differences in BMI z-score by sex and WIMD quintiles. Two-wayAnalysis of Covariances investigated the effect of sex and WIMD quintiles on grip strength and shuttles achieved in 20 m MSRT, adjusting for BMI z-score and maturation, repectively. Independent of sex, children in the middle quintile had a significantly higher mean BMI z-score (p = 0.029) than their least deprived counterparts. There was a significant increase in grip strength (p = 0.005) and20 m MSRT (boys p < 0.001; girls p = 0.028) between most and least deprived quintiles. Significant differences in 20 m MSRT score were more apparent with decreases in deprivation in boys.Overall, inequalities exist in health-related fitness by sex and deprivation. These results can be used to inform focused services to improve current and future health.     

Lean mass as a total mediator of the influence of muscular fitness on bone health in schoolchildren: a mediation analysis

This report aims to analyse the independent association of lean mass and muscle fitness with bone mineral content (BMC) and bone mineral density (BMD), and to examine whether the relationship between muscle fitness and bone health is mediated by lean mass. Body composition (by dual energy X-ray absorptiometry (DXA)), muscle fitness, physical activity, age and height were measured in 132 schoolchildren (62 boys, aged 8–11 years). Analysis of covariance tested differences in bone-related variables by lean mass and muscle fitness, controlling for different sets of confounders. Linear regression models fitted for mediation analyses examined whether the association between muscle fitness and bone mass was mediated by lean mass. Children with good performance in handgrip and standing long jump had better and worse bone health, respectively. These differences disappeared after controlling for lean mass. Children with high lean mass had higher values in all bone-related variables. In addition, the relationship between muscle fitness and bone mass was fully mediated by lean mass. In conclusion, the relationship between upper-limbs muscle fitness and bone health seems to be dependent on lean mass but not on muscle fitness. Schoolchildren with high lean mass have more BMC and BMD in all regions. Lean mass mediates the association between muscle fitness and bone mass.     

Fatness and fitness in relation to functional movement quality in overweight and obese children

This study aimed to investigate the independent and combined associations between several fatness indicators and fitness components with functional movement quality in overweight/obese children. A total of 56 children (33 girls, aged 8–12) classified as overweight/obese according to the World Obesity Federation standard cut points, participated in this study. Participants underwent assessments of fatness [body mass index (BMI), waist circumference, and bioelectrical impedance measures], fitness [1 repetition maximum bench and leg press, and ALPHA test battery], and functional movement quality [4 tests from Functional Movement Screen ^TM (FMS)]. All fatness outcomes, except waist circumference, were negatively associated with total FMS score, after controlling for cardiorespiratory fitness. Cardiorespiratory fitness, lower limbs muscle strength, and speed-agility were positively associated with the total FMS score, regardless of BMI. Our results suggest that children with greater fatness indicators demonstrate lower functional movement quality independently of their fitness level, whereas children with better fitness level (i.e. cardiorespiratory fitness, lower limbs muscular strength, and speed-agility) demonstrate greater functional movement quality independently of their fatness level. However, children´s weight status seems to be more determinant than their fitness level in terms of functional movement quality, whereas being fit seems to moderately attenuate the negative influence of fatness.     

控体重训练期膳食能量对古典摔跤运动员体脂、血液生化及肌肉力量的影响

目的：探讨减重训练期膳食能量对运动员血液生化、体成份及肌肉力量等指标的影响，从而更好地监控运动训练。方法：以8名摔跤运动员为研究对象，测试分3个阶段，即正常训练期、慢减体重期和快降体重期，主要测试膳食热能摄取、血液生化和最大握力等指标。结果：运动员在快降期热能摄取显著低于慢减体重期，且体脂百分比也有显著下降（P〈0．05）；与慢减期相比，运动员在快降期皮质醇和血尿素均有显著升高（P〈0．05），而血红蛋白、血清睾酮以及最大握力无明显差异；每千克体重能量摄取与血尿素有显著负相关性（r=-0．77），而与清CK和最大握力无显著相关性。结论：限制能量摄取仍是减重的主要手段之一，减少能量的摄取易导致机体分解代谢增强，且对该类项目的训练监控需考虑热能的因素。     

江西省幼儿体质评价与课程设置的分析

采用测量法、文献资料法和数理统计法,从身体形态和素质两个方面对江西省3-6岁幼儿进行体质测试分析与研究,结果发现：江西省幼儿体育存在幼儿园体育活动时间不充足、课程设置不合理、幼儿园体育设施不足等问题,并针对这些问题提出相应的建议,旨在为提高江西省幼儿体质提供依据。     

青岛市肥胖幼儿发生率和肥胖幼儿体质现状的调查分析

目的:探讨青岛市3～6岁幼儿肥胖的发生率和肥胖幼儿的体质情况,为预防幼儿肥胖和提高肥胖幼儿体质状况提供依据.方法:应用WHO推荐的身高标准体重≥120%作为肥胖判断标准,用比较分析的方法对随机抽取的青岛市3-6岁城乡男女幼儿进行调查分析.结果:青岛市肥胖幼儿检出率为10.8%,其中轻度、中度和重度检出率分别为6.6%、3.9%和0.4%.除网球掷远外,肥胖幼儿机能和身体素质的各项指标成绩明显低于正常体重幼儿.结论:肥胖幼儿的机能和身体素质的各项指标成绩从总体上低于正常体重组幼儿,提高肥胖幼儿的身体素质是幼儿健康中急需解决的问题.     

Relationship between weight status and cognition in children: A mediation analysis of physical fitness components

ABSTRACT

Cross-sectional study aimed to analyse differences in cognitive performance across fitness components categories (cardiorespiratory fitness [CRF], speed-agility and muscular fitness [MF]) and weight status in children, and to determine whether physical fitness mediates the association between body mass index (BMI) and cognitive performance. Fitness components and BMI were measured using standard procedures in 630 children aged 5-to-7 years from the provinces of Cuenca and Ciudad Real, Spain. BADyG was used to assess cognitive performance. We used ANCOVA models to test mean differences in cognition scores by BMI and fitness categories. Hayes’s PROCESS macro was used for mediation analyses. Children with normal weight scored better in spatial factor and general intelligence than their overweight/obese peers (p < 0.05), but differences were attenuated when controlling for CRF (p > 0.05). Children with better results in CRF and speed-agility scored better in all cognitive dimensions even after controlling for BMI (p < 0.05). Similarly, children with high MF obtained better scores in verbal factor (p < 0.05). All fitness components acted as mediators of the relationship between BMI and general intelligence (p < 0.05). These findings highlight the crucial role of fitness in minimising the negative effect of excess weight on children’s cognition.

Abbreviations: BMI: Body mass index; CRF: Cardiorespiratory fitness; MF: Muscular fitness; BADyG E1: Battery of general and differential aptitudes; SES: Socioeconomic status; SD: Standard deviation; IE: Indirect effect     

Relationships between functional movement screen scores,maturation and physical performance in young soccer players

The purpose of this study was to examine relationships between functional movement screen scores, maturation and physical performance in young soccer players. Thirty males (11–16 years) were assessed for maturation, functional movement screen scores and a range of physical performance tests (squat jump, reactive strength index protocol and reactive agility cut). Older players significantly outperformed younger participants in all tests (P < 0.05; effect sizes = 1.25–3.40). Deep overhead squat, in-line lunge, active straight leg raise and rotary stability test were significantly correlated to all performance tests. In-line lunge performance explained the greatest variance in reactive strength index (adjusted R² = 47%) and reactive agility cut (adjusted R² = 38%) performance, whilst maturation was the strongest predictor of squat jump performance (adjusted R² = 46%). This study demonstrated that variation of physical performance in youth soccer players could be explained by a combination of both functional movement screen scores and maturation.     

Accelerometer-measured daily physical activity related to aerobic fitness in children and adolescents

Abstract

Maximum oxygen uptake ([Vdot]O_2PEAK) is generally considered to be the best single marker for aerobic fitness. While a positive relationship between daily physical activity and aerobic fitness has been established in adults, the relationship appears less clear in children and adolescents. The purpose of this paper is to summarise recently published data on the relationship between daily physical activity, as measured by accelerometers, and [Vdot]O_2PEAK in children and adolescents. A PubMed search was performed on 29 October 2010 to identify relevant articles. Studies were considered relevant if they included measurement of daily physical activity by accelerometry and related to a [Vdot]O_2PEAK either measured directly at a maximal exercise test or estimated from maximal power output. A total of nine studies were identified, with a total number of 6116 children and adolescents investigated. Most studies reported a low-to-moderate relationship (r = 0.10–0.45) between objectively measured daily physical activity and [Vdot]O_2PEAK. No conclusive evidence exists that physical activity of higher intensities are more closely related to [Vdot]O_2PEAK, than lower intensities.     

Physical fitness of primary school children in relation to overweight prevalence and physical activity habits

Abstract

A cross-sectional study was carried out to analyse, through a limited number of fitness tests, the main conditioning and coordinative abilities in children aged 8–9 years, and their relationship with gender, anthropometric variables and physical activity habits. The height and weight of 256 boys and 241 girls were measured and information about physical activity habits was collected using a self-administered questionnaire. Physical performance was assessed by means of a few standardised tests: ‘sit & reach’, medicine-ball forward throw, standing long jump, 20 m running speed, and forward roll test. In both boys and girls, body weight and Body Mass Index (BMI) were positively correlated with the medicine-ball throw performances and negatively correlated for the standing long jump and speed tests, while no association was found with tests measuring back flexibility and total body coordination. Daily physical activity and participation in sport were not significantly correlated with body weight and BMI, but were positively associated with children's motor performance. The standardised fitness tests selected in the current study have been found to be suitable to identify fitness levels of primary school children. Thanks to their limited number and ease of measurement, they can be used in any school context to classify children and for monitoring the effects of targeted interventions promoting physical activity.     

Effects of an afterschool community center physical activity program on fitness and body composition in obese youth

Physical activity (PA) promotes health in obese youth and is an important adjunct to medical weight management. Access to structured fitness programmes for obese, low-income youth is limited and potential benefits of such programmes are poorly understood. We describe an urban afterschool fitness programme for obese youth and participants’ changes in fitness and body composition. A case series of 30 youth (age: 11.5 ± 2.5 years) with BMI ≥95th percentile and physician referral received a 24-wk programme scholarship. The programme, offered 4 times a week for 90-min.session, included aerobic, strength, and self-organised PA. Primary outcomes, measured at baseline (BL) time 1 (4–8 wk) and time 2 (12–16 wk) were BMI, per cent body fat (%BF), fat-free mass (FFM), heart rate during a treadmill test, and muscular strength (one repetition maximum (1RM)) and endurance (reps at 70% of 1RM) on the leg press (LP) and chest press (CP). Average participation was 1.5 ± 0.6 visits per week for 18.7 ± 6.5 weeks. Between BL and time 2, LP and CP 1RM and endurance significantly improved (P < 0.05). Additionally, there was a significant interaction for %BF with boys losing 5.2% (P > 0.05) while girls lost 0% (>0.05). Obese youth attending an urban fitness programme for at least three months improved strength and body composition, but average attendance was below planned levels.     

Cardiorespiratory fitness,fatness, and cardiovascular disease risk factors in children and adolescents from Porto

Abstract

In the present study, we examined different categories of cardiorespiratory fitness and obesity and their relationship with risk of cardiovascular disease (CVD) factors in youth. We hypothesized that youngsters with low cardiorespiratory fitness would be at greater risk of CVD risk factors, whether they are obese or not. This study was carried out as a part of a longitudinal research project conducted in the Porto and Braga districts, Portugal, with children and adolescents aged 10–16 years of age. A total of 392 children (173 boys, 219 girls) participated in the study. We used a chi-square test to analyse the relationship between the participants' cardiorespiratory fitness and body weight (non-overweight or overweight/obese). For the purpose of this study, a new variable with four groups was created: non-overweight +unfit (37.4%), non-overweight + fit (35%), overweight/obese + unfit (11%) and overweight/obese + fit (10%). A one-way analysis of variance was used to compare the differences according to fitness and fatness groups. The main finding of this study was that regardless of fatness, participants with higher cardiorespiratory fitness presented with a lower prevalence of CVD risk factors.     

The impact of physical activity and fitness on academic achievement and cognitive performance in children

The potential for physical activity and fitness to improve cognitive function, learning and academic achievement in children has received attention by researchers and policy makers. This paper reports a systematic approach to identification, analysis and review of published studies up to early 2009. A three-step search method was adopted to identify studies that used measures of physical activity or fitness to assess either degree of association with or effect on a) academic achievement and b) cognitive performance. A total of 18 studies including one randomised control trial, six quasi-experimental and 11 correlational studies were included for data extraction. No studies meeting criteria that examined the links between physical activity and cognitive function were found. Weak positive associations were found between both physical activity and fitness and academic achievement and fitness and elements of cognitive function, but this was not supported by intervention studies. There is insufficient evidence to conclude that additional physical education time increases academic achievement; however there is no evidence that it is detrimental. The quality and depth of the evidence base is limited. Further research with rigour beyond correlational studies is essential.     

The relationship between strength asymmetries and jumping performance in professional volleyball players

Knee peak torque (PT) is associated to jump performance in volleyball players. It is not clear whether muscle strength imbalances of the knee joint can influence jump performance. The purpose of study was to analyse the association between PT and knee muscular imbalances with jump performance in professional volleyball players. Eleven elite male volleyball players (90.3 ± 9.7 kg body mass and 1.94 ± 0.06 m height) were evaluated in an isokinetic dynamometer at speeds of 60, 180 and 300 deg/s. Muscle strength imbalances were obtained through calculation of contralateral deficit between limbs and the conventional ratio (hamstrings/quadriceps). Countermovement jump (CMJ) was performed on a force plate to calculate mechanical power and height. Association was found between knee extensor PT at 180 deg/s with CMJ power (r = 0.610, p = 0.046). Conventional ratio at 300 deg/s showed negative association with CMJ (r = ?0.656, p = 0.029). The optimal ratio between knee extensors PT in relation to the flexors PT is associated with the greater mechanical power in CMJ. Contralateral deficit does not seem to be associated with the CMJ performance. Considering the knee extensor PT is associated with CMJ power, our findings suggest that strength-based training in volleyball athletes should not omit the conventional muscle ratio.     

Objectively measured physical activity,body composition and physical fitness: Cross-sectional associations in 9- to 15-year-old children

The aim of this study was to examine and quantify the cross-sectional associations of body composition (BC), physical activity (PA) and sedentary time (ST) with physical fitness (PF) in children and adolescents. A sample of 594 Finnish students (56% girls), aged 9–15 (12.4?±?1.3 years) were selected for a study performed in 2013. The measurements of the Move! monitoring system for physical functional capacity were used to measure cardiorespiratory and musculoskeletal fitness and fundamental movement skills. Moderate-to-vigorous PA (MVPA) and ST were measured objectively with an accelerometer and BC by a bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations were explored with a linear regression model. In general, FMI had statistically significant negative associations, while FFMI and MVPA had positive associations with PF. No statistically significant associations were observed between ST and PF. In general, FMI had the strongest association with PF, although some variation occurred with sex and PF component. However, associations were practically relevant only in 20-m shuttle run, push-up, curl-up and 5-leaps test. For example, approximately 5?kg increase in fat mass in 155?cm tall children was estimated to correspond to 8 laps in 20-m shuttle run. Similar increase in fat-free mass corresponded to +4 and +6 laps, and 10?min increase in daily MVPA +3 and +2 laps in 20-m shuttle run, in boys and girls, respectively. Understanding these associations is necessary when interpreting children’s PF and designing interventions.     

Identifying the optimal body shape and composition associated with strength outcomes in children and adolescent according to place of residence: An allometric approach

The purpose of the study was to identify the optimal body shape and composition associated with physical fitness levels of children living in urban and rural areas of Italy. A total of 7102 children (11–14 years) were assessed for weight, height, percentage body fat (FM%), sit-and-reach flexibility (SAR), standing broad jump (SBJ) and sit-ups (SUP). A multiplicative allometric model, Y = a · mass^k1 · height^k2 ·ε, was used to predict the physical outcome variables Y = SBJ and SUP. The model was expanded to incorporate FM% and SAR as follows Y = a · mass^k1 · height^k2 · FM%^k3 · exp(b· FM% + c· SAR) ·ε. Note that FM% was incorporated as a “gamma function” that allows an initial growth, and subsequent decline in Y as FM% increases in size. Although having an ectomorph body shape appears advantageous, being too thin appears detrimental to the strength outcomes. Being flexible would also benefit physical fitness levels. Finally, our results indicate that ursban children aged 11–14 have superior strength outcomes compared with rural children, having controlled for differences in body shape and composition, a finding that may be associated with rural environments having fewer exercise facilities compared with urban conurbations.     

影响儿童青少年最大有氧活动能力的因素(综述)

儿童青少年在青春发育期前后,机体各组织器官的功能都在迅速的提高.儿童青少年VO2max的研究和测定,可以综合反映儿童青少年体格状况、有氧运动机能,是判断儿童青少年发育水平及不同环境因素对儿童青少年体质影响的比较理想的动态机能指标.通过综述了前人对儿童青少年最大有氧活动能力的研究,特别是影响其有氧能力的遗传因素、个体状况、环境因素和训练因素在儿童青少年生长发育期的作用和特点,使大家正确认识儿童青少年这一能力的发展,关心儿童青少年的健康成长.