基于加速度传感器的学龄前儿童体力活动簇集特征研究

目的以客观测量的体力活动水平为基础,分析不同持续时间活动的频率及其占总活动时间的比例,从而掌握学龄前儿童体力活动簇集特征。方法根据知情、自愿原则,在上海市杨浦和宝山2个区共招募306名学龄前儿童为受试者,通过连续7 d佩戴加速度传感器ActiGraph GT3X+测量其日常体力活动水平,在此基础上将每次体力活动按强度和持续时间进行分类,并统计不同持续时间的活动平均每天出现的频率及其占总累积活动的比例。结果共有146名受试者[男85名,女61名;平均月龄为(57.7±5.0)月]7 d测量数据均有效,被纳入最终统计分析。发现采样间隔为1 s时,学龄前儿童平均每次体力活动持续时间≤4 s,且70%以上的中等强度和大强度体力活动持续时间为2~3 s。结论学龄前儿童体力活动以持续时间较短的零星活动为主。为准确测量学龄前儿童体力活动,特别是中到大强度体力活动水平,宜采用较短的加速度传感器采样间隔(如3 s或更短时间)。     

Using accelerometry to quantify deceleration during a high-intensity soccer turning manoeuvre

Abstract

The mechanics of cutting movements have been investigated extensively, but few studies have considered the rapid deceleration phase prior to turning which has been linked to muscle damage. This study used accelerometry to examine the influence of turning intensity on the last three steps of a severe turn.

Ten soccer players performed 135° “V” cuts at five different intensities. Resultant decelerations were recorded from a trunk-mounted tri-axial accelerometer. Lower limb kinematics and ground reaction forces (GRF) from the pivot foot-ground contact (FGC) were also monitored.

Average peak trunk decelerations were larger at the two preceding steps (4.37 ± 0.12 g and 4.58 ± 0.11 g) compared to the PIVOT step (4.10 ± 0.09 g). Larger peak joint flexion angular velocities were observed at PRE step (ankle: 367 ± 192 deg.s^?1; knee 493 ± 252 deg.s^?1) compared to PIVOT step (ankle 255 ± 183 deg.s^?1; knee 377 ± 229 deg.s^?1). Turn intensity did not influence peak GRF at PIVOT step.

This study highlights the importance of steps prior to turning and their high-frequency loading characteristics. It is suggested that investigations of lower limb loading during turning should include this deceleration phase and not focus solely on pivot FGC.     

An examination of the Clegg impact hammer test with regard to the playing performance of synthetic sports surfaces

One of the tests used to evaluate the performance of sports surfaces measures the peak deceleration of a rigid mass during contact with the surface, after being dropped from a set height. It is widely used and is included in a number of international standards. The test was carried out using two drop heights on four different designs of artificial cricket pitch, with a full set of acceleration data being collected over the duration of impact. These data were then integrated twice with respect to time to produce velocity and displacement information. Oblique impacts of cricket balls were also carried out and analysed using a high-speed video system to evaluate the playing performance of each pitch design. It was found that, although the pitches gave quite different readings of peak deceleration, they produced similar values for coefficient of restitution and were therefore considered to ‘play’ in a very similar way. This was due to a high peak deceleration reading being accompanied by a short contact time and low peak deceleration being accompanied by a long contact time, meaning that the change in momentum was similar in both cases. It was concluded that for accelerometer tests to be useful, all the acceleration-time data should be analysed, rather than the peak value alone.     

Decision boundaries and receiver operating characteristic curves: New methods for determining accelerometer cutpoints

Abstract

We propose and evaluate the utility of an alternative method (decision boundaries) for establishing physical activity intensity-related accelerometer cutpoints. Accelerometer data collected from seventy-six 11- to 14-year-old boys during controlled bouts of moderate- and vigorous-intensity field physical activities were assessed. Mean values and standard deviations for moderate- and vigorous-intensity activities were obtained and normal equivalents generated. The decision boundary (the point of intersection of overlapping distributions) was used to create a lower-bound vigorous-intensity cutpoint. Receiver operating characteristic (ROC) curves compared the sensitivity and specificity of the new cutpoint and mean values with the actual activity. There was a 96.5% probability that participants performing vigorous-intensity physical activity were accurately classified when using the decision boundary of 6700 counts per minute, in contrast to the 50% accurately classified when the mean value was used. Inspection of the empirical ROC curve indicated that the decision boundary provided the optimal threshold to distinguish between moderate and vigorous physical activity for this dataset. In conclusion, decision boundaries reduced the error associated with determining accelerometer threshold values. Applying these methods to accelerometer data collected in specific populations will improve the precision with which accelerometer thresholds can be identified.     

Sedentary time and vigorous physical activity are independently associated with cardiorespiratory fitness in middle school youth

Abstract

The purpose of this cross-sectional study was to examine the relationship between objectively measured physical activity, sedentary time, and cardiorespiratory fitness in a diverse sample of youth. Participants were recruited from three middle schools and completed assessments of height, weight, cardiorespiratory fitness, and wore an accelerometer for a minimum of four days. Hierarchical general linear models controlling for age, body mass index (BMI) percentile, and sex were used to evaluate the association of time (minutes per day) spent sedentary, and in moderate physical activity and vigorous physical activity with cardiorespiratory fitness (i.e., heart rate response [beats per minute], dependent variable). Results indicated age (β = –0.16, P < 0.05), BMI percentile (β = 0.33, P <0.05), being male (β = 0.17, P < 0.05), sedentary time (β = 0.11, P <0.05), moderate (β = –0.03, P > 0.05) and vigorous (β = –0.22, P < 0.05) physical activity explained 29% of the variance in cardiorespiratory fitness. Evaluation of fitness among high sedentary/high vigorous, high sedentary/low vigorous, low sedentary/low vigorous, and low sedentary/high vigorous groups (defined by the median split) showed that high levels of vigorous activity removed the detrimental effect of high levels of sedentary time on cardiorespiratory fitness. These analyses suggest that the negative impact of sedentary time can be mitigated by engaging in vigorous activity.     

Reliability and criterion validity of the Self-Administered Physical Activity Checklist in Greek children

Abstract

The purpose of this study was to assess the test–retest reliability and criterion validity the Self-Administered Physical Activity Checklist (SAPAC) translated into the Greek language. To evaluate reliability, 72 students (35 girls and 37 boys) of the fifth and sixth grade completed SAPAC on two separate occasions, two weeks apart. Internal consistency was determined with Cronbach alpha coefficient and test–retest reliability with the intraclass correlation coefficient (ICC). To evaluate criterion validity, the RT3 Research Tracker accelerometer was used as standard measure, in 90 randomly selected Greek children (51 girls and 39 boys), aged between 10 and 13. Each subject participated for two consecutive days. On day one, an accelerometer was fitted when school started. On day two, the accelerometers were returned and each subject completed the questionnaire. The internal consistency and the test–retest reliability of SAPAC on total metabolic equivalent (MET) score, MET score of low physical activities (LPA) and MET score of moderate to vigorous physical activities (MVPA) were very satisfactory (all Cronbach's alpha > 0.87, and all ICC > 0.85, P <0.001). The Kendall's tau-b test revealed that the degree of agreement between SAPAC and RT3 accelerometer on total MET score and MET score of MVPA were 0.31 and 0.37, respectively (P <0.01). It was concluded that the Greek translated version of SAPAC is a reliable questionnaire that provides valid estimates of total, as well as moderate to vigorous activities MET scores.     

应用三轴加速度计（GT3X+）监测广州高中生日常体力活动的研究

目的:了解学生日常体力活动现状,探讨影响学生日常体力活动的因素。方法:应用ActiGraPh GT3X-Plus三轴加速度计对18名男性健康高中生进行为期一周的日常体力活动监测。结果:学生有四成以上时间以静态活动状态为主,平时日和周末日坐的时间>躺的时间>站的时间(P<0.001),而休息日则躺的时间>坐的时间>站的时间(P<0.001)。学生从事中等强度及其以上活动时间仅占全天总时间的10%左右,平时日和周末日静态活动强度时间>中等强度时间>轻体力活动时间>大强度时间>剧烈活动时间,休息日为静态活动强度时间>轻体力活动时间>中等强度时间>大强度时间>剧烈活动时间,经检验不同强度时间之间均有非常显著性差异,P<0.001。休息日能量消耗(339.3±145.7kcal)明显低于平时日(515.3±166.0kcal)和周末日能量消耗(510.9±164.6kcal),P<0.01具有非常显著性差异。双因素方差分析显示,活动日对学生躺时间(P<0.001)、静态活动时间(P<0.01)、中等强度活动时间(P<0.01)和全天能量消耗(P<0.01)有显著性影响;年级仅对静态活动时间(P<0.05)、轻体力活动时间(P<0.05)和剧烈活动时间(P<0.05)有影响;年级*活动日期双重因素对静态活动时间(P<0.05)有显著影响。结论:高中男生主要以静态生活方式为主,且体力活动不足。上学日和非上学日对学生的日常体力活动影响显著。在今后对于学生日常体力活动的研究中不必过多地考虑年级因素的影响,但有必要按活动日的不同进行具体分析。     

An in-plane low-noise accelerometer fabricated with an improved process flow

We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow, by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor. The improved flow greatly lowers the footing effect during deep reactive ion etching （DRIE）, and increases the proof mass by 54% compared to the traditional way, resulting in both improved device quality and a higher yield rate. Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair, which eliminates the nonlinear behavior by fixing the parallel-plate gap. The damping coefficient of the sensing motion is low due to the slide-film damping. A large proof mass is made using DRIE, which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage. The theoretical Brownian noise floor is 0.47 μg/Hz^1/2 at room temperature and atmospheric pressure. The tested frequency response of a prototype complies with the low damping design scheme. Output data for input acceleration from -1 g to 1 g are recorded by a digital multimeter and show very good linearity. The tested random bias of the prototype is 130 μg at an averaging time of around 6 s.     

轻度智障儿童基本运动技能与体力活动水平的关系

目的调查轻度智障儿童基本运动技能(FMS)与体力活动水平,探讨二者之间的关系,为该群体运动参与能力的提升及其健康促进提供指导思路。方法选取上海市65名轻度智障儿童作为调查对象,运用TGMD-2和ActiGraph GT3X+三轴加速度传感器分别对其FMS及体力活动水平进行测量和评价,对相关数据进行统计分析。结果轻度智障儿童FMS平均总得分为(67.82±7.31)分,其中位移技能得分显著高于物理控制技能(P<0.01),男生位移技能得分显著高于女生(P<0.05),但物体控制技能无显著性别差异(P>0.05)。15.6%的轻度智障儿童能满足每天60 min中高强度体力活动(MVPA)推荐量,男生平均每天MVPA时间显著高于女生(P<0.01),周末日体力活动时间显著高于上学日(P<0.01)。总体上轻度智障儿童的低强度体力活动(LPA)、MVPA和总体力活动(TPA)时间与FMS得分均呈正相关(r=0.351~0.547,P<0.05)。FMS得分对轻度智障儿童平均每天MVPA时间、TPA时间具有解释意义(R^2=0.381,P<0.01;R^2=0.409,P<0.01)。位移技能是解释每天MVPA时间的唯一变量(β=0.490,P<0.01)。结论轻度智障儿童的FMS发展与体力活动水平整体呈正相关关系,基于该群体技能发展层面的体力活动促进是该领域相关研究的重要方向。     

Associations of physical activity,sedentary time,and physical fitness with mental health during pregnancy: The GESTAFIT project

PurposeThis study was aimed to analyze the associations of objectively measured physical activity (PA), sedentary time, and physical fitness with mental health in the early second trimester (16 ± 2 gestational weeks) of pregnancy.MethodsFrom 229 women initially contacted, 124 pregnant women participated in the present cross-sectional study. Data were collected between November 2015 and March 2017. The participants wore Actigraph GT3X+ Triaxial accelerometers for 9 consecutive days to objectively measure their PA levels and sedentary time. A performance-based test battery was used to measure physical fitness. Self-report questionnaires assessed psychological ill-being (i.e., negative affect, anxiety, and depression), and psychological well-being (i.e., emotional intelligence, resilience, and positive affect). Linear regression analyses were adjusted for age, educational level, accelerometer wear time, miscarriages, and low back pain.ResultsModerate-to-vigorous PA was negatively associated with depression (β = –0.222, adjusted R² = 0.050, p = 0.041). Higher levels of sedentary time were negatively associated with positive affect (β = –0.260, adjusted R² = 0.085, p = 0.017). Greater upper-body flexibility was positively associated with better emotional regulation (β = 0.195, adjusted R²= 0.030, p = 0.047). The remaining associations were not significant (all p > 0.05).ConclusionAn active lifestyle characterized by higher levels of moderate-to-vigorous PA and lower levels of sedentary time during pregnancy might modestly improve the mental health of pregnant women. Although previous research has focused on the benefits of cardiorespiratory exercise, the present study shows that only upper-body flexibility is related to emotional regulation in early pregnant women. If the present findings are corroborated in further experimental research, physical exercise programs should focus on enhancing flexibility to promote improvements in emotional regulation during early second-trimester of pregnancy.