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.     

Time-restricted feeding in young men performing resistance training: A randomized controlled trial†

A randomized controlled trial was conducted to examine eight weeks of resistance training (RT) with and without time-restricted feeding (TRF) in order to assess nutrient intake and changes in body composition and muscular strength in young recreationally active males. The TRF programme consisted of consuming all calories within a four-hour period of time for four days per week, but included no limitations on quantities or types of foods consumed. The RT programme was performed three days per week and consisted of alternating upper and lower body workouts. For each exercise, four sets leading to muscular failure between 8 and 12 repetitions were employed. Research visits were conducted at baseline, four, and eight weeks after study commencement. Measurements of total body composition by dual-energy X-ray absorptiometry and muscle cross-sectional area by ultrasound were obtained. Upper and lower body strength and endurance were assessed, and four-day dietary records were collected. TRF reduced energy intake by ～650?kcal per day of TRF, but did not affect total body composition within the duration of the study. Cross-sectional area of the biceps brachii and rectus femoris increased in both groups. Effect size data indicate a gain in lean soft tissue in the group that performed RT without TRF (+2.3?kg, d?=?0.25). Upper and lower body strength and lower body muscular endurance increased in both groups, but effect sizes demonstrate greater improvements in the TRF group. Overall, TRF reduced energy intake and did not adversely affect lean mass retention or muscular improvements with short-term RT in young males.     

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.     

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。     

阻力训练及超等长阻力训练对下肢肌肉活性和力量的影响

目的:观察阻力训练和超等长阻力训练后下肢肌肉力量变化,比较肌肉激活模式的不同.方法:将16名男性篮球运动员随机分成两组,分别实施8周下肢阻力训练和超等长阻力训练.采用3-D测力台测试训练前、后最大随意收缩值,用表面肌电记录训练前、后6次重复训练动作的胫骨前肌、腓肠肌外侧头、股直肌、股外侧肌、股二头肌的激活信号,计算积分肌电值和髋、膝、踝关节周围拮抗肌共激活.结果:两组下肢肌肉力量均显著提高,阻力训练组效果较明显.超等长阻力训练组肌肉活性显著高于阻力训练组.训练后超等长阻力训练组肌肉活性出现适应性变化,髋、踝关节拮抗肌共激活显著升高,膝关节拮抗肌共激活训练前、后没有显著性差异.阻力训练组训练前、后肌肉活性及拮抗肌共激活没有显著变化.结论:超等长阻力训练有助于提高肌肉间协调性,可以优化肌肉动作的运动策略.     

Analysis of the training load during a hypertrophy-type resistance training programme in men and women

Abstract

The purpose of this study was to analyze the specific training load during a resistance training (RT) programme designed to increase muscular hypertrophy in men and women. Thirty-four women (22.7 ± 4.1 years, 58.8 ± 11.9 kg, 162.6 ± 6.2 cm and 22.1 ± 3.6 kg.m^?2) and 30 men (22.7 ± 4.4 years, 68.4 ± 9.0 kg, 174.5 ± 6.6 cm and 22.5 ± 2.4 kg.m^?2) underwent a supervised RT programme that was divided into two phases of 8 weeks each. Training consisted of 10–12 exercises performed with three sets of 8–12 repetitions at repetition maximum resistances performed 3 times per week on nonconsecutive days. There was a significant (P < 0.05) main effect for gender by time interaction for average training load of all the exercises performed in the first 8 weeks of RT with women showing a higher relative increase than men (+43.6% vs. +32.5%, respectively). This result was not observed during the second 8-week phase of the RT programme during which no significant gender by time interaction (P > 0.05) was shown with both genders having a similar relative increase (+28.7% vs. +24.3%, respectively). Women had a higher increase than men in specific average training load of the upper limb exercises during both the first 8 weeks of training (+30.2% vs. +26.6%, respectively) and the second 8 weeks of training (+31.1% vs. +25.3%, respectively). We conclude that the adaptation in specific training load is influenced by gender.     

跳跃运动员起跳过程的肌肉工作方式与专项力量训练

本文对跳跃运动员起跳过程的肌肉工作方式特点进行了运动学、动力学探讨、观点新颖，对跳跃运动员的专项力量训练进行了再认识，并介绍了一些训练手段和方法，对指导科学训练及提高专项运动成绩有实际意义。     

Water training in postmenopausal women: Effect on muscular strength

Abstract

The purpose of this study was to determine the effectiveness of a swimming programme and a calisthenics and resistance water training programme, which included aerobic and resistance components, on muscle strength and body weight in postmenopausal women. Both were carried out over a period of 12 months. Ninety-three subjects were randomly assigned to swimming group (SG; n=29), calisthenics and resistance group (CRG; n=34) and control group (CG; n=30). Mean upper-extremities biokinetic force (MF), power (MP) and work (MW) were measured by a biokinetic swim bench (Biometer Swim Bench, Sport Fahnemann). Maximal isometric forces of the trunk flexors (ITF) and knee extensors (IKE) were measured by an isometric strain-gauge dynamometer (T.K.K. 5402, Takei Scientific Instruments Co. Ltd.). Countermovement jump height (CMJ) was evaluated using the Ergojump Bosco System. Energy consumption was measured using a self-administrated food frequency questionnaire (Sanocare Human Systems L.S., Madrid. Spain). Body mass index (BMI) was also measured. CRG improved significantly (p≤0.05) MF increased by 7.92%, MP by 9.08% and MW by 9.3%. SG and CRG demonstrated a significant decrease in BMI (?2.08 and ?2.75% respectively). SG, CRG and CG showed a significant decrease in ITF (?5.07, ?11.34 and ?24.73% respectively) and IKE (?7.99, ?12.77 and ?29.75% respectively). This decrease was significantly greater in CG compared with SG and CRG. There were no significant changes in CMJ in any group. These results indicate that water exercise has significant implications, improving some health-related components of fitness in postmenopausal women.     

Does a land-based compensatory strength-training programme influences the rotator cuff balance of young competitive swimmers?

Abstract

During the repeated execution of the swimming strokes, the shoulder adductor and internal rotator muscles have a tendency to become proportionally stronger when compared to their antagonist group. This can lead to muscle imbalances. The aim of this study was to examine the effects of a compensatory training programme on the strength and balance of shoulder rotator muscles in young swimmers. A randomized controlled trial design was used. Forty male swimmers took part in the study and were randomly divided into two groups: an experimental group (n?=?20) and a training group (n?=?20). A control group (n?=?16) of young sedentary male students was also evaluated. The experimental group subjects participated in a 16-week shoulder-strength programme with Thera-Band^® elastic bands; the training group was restricted to aquatic training. Peak torque of shoulder internal rotator and external rotator (ER) was measured at baseline and after 16 weeks. Concentric action at 1.04?rad?s^?1 (3 reps) and 3.14?rad?s^?1 (20 reps) was measured using an isokinetic dynamometer. The strength-training programme led to an improvement of the ER strength and shoulder rotator balance in the experimental group (data from both shoulders at 1.04?rad?s^?1). Moreover, concentric action at 3.14?rad?s^?1 presented significant differences only for the dominant shoulder. Findings suggest that the prescribed shoulder-strengthening exercises could be a useful training option for young competitive swimmers. They can produce an increase in absolute strength values and greater muscle balance in shoulder rotators.     

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.     

运动员的膳食评价

介绍了运动员食物和营养素摄入的评价方法,主要包括4个方面：（1）食物摄入量的评价方法,（2）膳食评价中的常见问题,（3）运动员食物摄入量评价的特殊问题,（4）膳食分析。膳食评价的方法有很多,如：膳食记录法、24 h膳食回顾法和食物频率问卷调查法。在膳食评价过程中,误报、零食、报告的坦率性以及评价的时间范围,都是需要注意的问题。另外,还要考虑运动员不同训练周期阶段的特殊问题、液体摄入、营养补充品和体重管理的问题。为了更有效地进行膳食评价分析,需选择恰当的食物成分数据库和营养分析软件。准确和全面的营养评价对客观地了解运动员的营养状况并提出膳食建议非常重要。     

EMSF肌肉功能电刺激应用的研究

本文通过国外对EMSF（肌肉功能电刺激）的研究应用及“力王”多年来的国内应用情况进行研究和分析，旨在拓展我国力量训练的有效方法。     

简易力量测试法和等速肌力测试相关性研究

目的:探讨体质监测中握力、下肢蹬踏爆发力作为力量素质的简易测试法能否反映人体的力量素质。方法:随机抽取311例上海市普通市民,进行握力,下肢蹬踏爆发力,肘、膝关节运动速度为60°/s的等速向心力量测试。对握力与肘关节等速向心力量,下肢蹬踏爆发力与膝关节等速向心力量进行相关性统计分析。结果:握力与肘关节屈肌峰力矩正相关(r=0.815),与肘关节屈肌相对峰力矩正相关(r=0.712);下肢蹬踏爆发力与膝关节屈肌峰力矩正相关(r=0.764),与伸肌峰力矩正相关(r=0.766);结论:握力、下肢蹬踏爆发力可以作为人体力量素质的简易测试方法并可应用于体质监测工作中。     

Effect of vibratory stimulation training on maximal force and flexibility

In this study, we investigated a new method of training for maximal strength and flexibility, which included exertion with superimposed vibration (vibratory stimulation, VS) on target muscles. Twenty‐eight male athletes were divided into three groups, and trained three times a week for 3 weeks in one of the following conditions: (A) conventional exercises for strength of the arms and VS stretching exercises for the legs; (B) VS strength exercises for the arms and conventional stretching exercises for the legs; (C) irrelevant training (control group). The vibration was applied at 44 Hz while its amplitude was 3 mm. The effect of training was evaluated by means of isotonic maximal force, heel‐to‐heel length in the two‐leg split across, and flex‐and‐reach test for body flexion. The VS strength training yielded an average increase in isotonic maximal strength of 49.8%, compared with an average gain of 16% with conventional training, while no gain was observed for the control group. The VS flexibility training resulted in an average gain in the legs split of 14.5 cm compared with 4.1 cm for the conventional training and 2 cm for the control groups, respectively. The ANOVA revealed significant pre‐post training effects and an interaction between pre‐post training and ‘treatment’ effects (P< 0.001) for the isotonic maximal force and both flexibility tests. It was concluded that superimposed vibrations applied for short periods allow for increased gains in maximal strength and flexibility.