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Fulltext A new sensors-based covert channel on android

Al-Haiqi A, Ismail M, Nordin R

ScientificWorldJournal, 2014;2014:969628.
PMID: 25295311 DOI: 10.1155/2014/969628

Covert channels are not new in computing systems, and have been studied since their first definition four decades ago. New platforms invoke thorough investigations to assess their security. Now is the time for Android platform to analyze its security model, in particular the two key principles: process-isolation and the permissions system. Aside from all sorts of malware, one threat proved intractable by current protection solutions, that is, collusion attacks involving two applications communicating over covert channels. Still no universal solution can countermeasure this sort of attack unless the covert channels are known. This paper is an attempt to reveal a new covert channel, not only being specific to smartphones, but also exploiting an unusual resource as a vehicle to carry covert information: sensors data. Accelerometers generate signals that reflect user motions, and malware applications can apparently only read their data. However, if the vibration motor on the device is used properly, programmatically produced vibration patterns can encode stolen data and hence an application can cause discernible effects on acceleration data to be received and decoded by another application. Our evaluations confirmed a real threat where strings of tens of characters could be transmitted errorless if the throughput is reduced to around 2.5-5 bps. The proposed covert channel is very stealthy as no unusual permissions are required and there is no explicit communication between the colluding applications.

Matched MeSH terms: Accelerometry/methods; Accelerometry/trends*
Physical Activity Measurement by Accelerometry Among Older Malay Adults Living in Semi-Rural Areas-A Feasibility Study

Zainol Abidin N, Brown WJ, Clark B, Muhamed AM, Singh R

J Aging Phys Act, 2016 10;24(4):533-539.
PMID: 26964887

We evaluated feasibility of physical activity measurement by accelerometry among older Malay adults living in semi-rural areas in Malaysia. Results showed that 95% of 146 participants (aged [SD] 67.6 [6.4] years) were compliant in wearing the accelerometer for at least five days. Fifteen participants were asked for re-wear the accelerometer because they did not have enough valid days during the first assessment. Participants wore the accelerometer an average of 15.3 hr in a 24-hr day, with 6.5 (1.2) valid wear days. No significant difference in valid wear day and time was found between men and women. Participants who are single provide more valid wear days compared with married participants (p < .05), and participants with higher levels of education provide longer periods of accelerometer wearing hours (p < .01). Eighty-seven percent of participants reported 'no issues' with wearing the meter. This study suggests that accelerometry is a feasible method to assess the physical activity level among older Malay adults living in semi-rural areas.

Matched MeSH terms: Accelerometry/instrumentation*
Fulltext Validity of low-cost measures for global surveillance of physical activity in pre-school children: The SUNRISE validation study

Mwase-Vuma TW, Janssen X, Okely AD, Tremblay MS, Draper CE, Florindo AA, et al.

J Sci Med Sport, 2022 Dec;25(12):1002-1007.
PMID: 36270900 DOI: 10.1016/j.jsams.2022.10.003

OBJECTIVES: To validate parent-reported child habitual total physical activity against accelerometry and three existing step-count thresholds for classifying 3 h/day of total physical activity in pre-schoolers from 13 culturally and geographically diverse countries.
DESIGN: Cross-sectional validation study.
METHODS: We used data involving 3- and 4-year-olds from 13 middle- and high-income countries who participated in the SUNRISE study. We used Spearman's rank-order correlation, Bland-Altman plots, and Kappa statistics to validate parent-reported child habitual total physical activity against activPAL™-measured total physical activity over 3 days. Additionally, we used Receiver Operating Characteristic Area Under the Curve analysis to validate existing step-count thresholds (Gabel, Vale, and De Craemer) using step-counts derived from activPAL™.
RESULTS: Of the 352 pre-schoolers, 49.1 % were girls. There was a very weak but significant positive correlation and slight agreement between parent-reported total physical activity and accelerometer-measured total physical activity (r: 0.140; p = 0.009; Kappa: 0.030). Parents overestimated their child's total physical activity compared to accelerometry (mean bias: 69 min/day; standard deviation: 126; 95 % limits of agreement: -179, 316). Of the three step-count thresholds tested, the De Craemer threshold of 11,500 steps/day provided excellent classification of meeting the total physical activity guideline as measured by accelerometry (area under the ROC curve: 0.945; 95 % confidence interval: 0.928, 0.961; sensitivity: 100.0 %; specificity: 88.9 %).
CONCLUSIONS: Parent reports may have limited validity for assessing pre-schoolers' level of total physical activity. Step-counting is a promising alternative - low-cost global surveillance initiatives could potentially use pedometers for assessing compliance with the physical activity guideline in early childhood.

Matched MeSH terms: Accelerometry*
Fulltext Multisensor automatic balancing model for DARwIn-OP on uneven terrain

Muhamad Khuzaifah Ismail, Meng Cheng Lau, Mohammad Faidzul Nasrudin, Haslina Arsha

Pertanika Journal of Science & Technology, 2017;25(106):181-188.
MyJurnal

The walking of a humanoid robot needs to be robust enough in order to maintain balance in a dynamic environment especially on uneven terrain. A walking model based on multi-sensor is proposed for a Robotis DARwIn-OP robot named as Leman. Two force sensitive resistor (FSRs) on both feet equipped to Leman to estimate the zero moment point (ZMP) alongside with accelerometer and gyrosensor embedded in the body for body state estimation. The results show that the FSRs can successfully detect the unbalanced walking event if the protuberance exists on the floor surface and the accelerometer and gyrosensor (Inertial Measurement Unit, IMU) data are recorded to tune the balancing parameter in the model.

Matched MeSH terms: Accelerometry
Fulltext Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection

Luo D, Ibrahim Z, Ma J, Ismail Z, Iseley DT

Sensors (Basel), 2016 Dec 16;16(12).
PMID: 27999245 DOI: 10.3390/s16122149

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering.

Matched MeSH terms: Accelerometry
Fulltext The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice

Chang KM, Chun YT, Chen SH, Lu L, Su HT, Liang HM, et al.

Sensors (Basel), 2016 Jul 20;16(7).
PMID: 27447641 DOI: 10.3390/s16071126

Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20-30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were -0.440, -0.369, and -0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice.

Matched MeSH terms: Accelerometry/methods*
Fulltext Heart Rate Measures From Wrist-Worn Activity Trackers in a Laboratory and Free-Living Setting: Validation Study

Müller AM, Wang NX, Yao J, Tan CS, Low ICC, Lim N, et al.

JMIR Mhealth Uhealth, 2019 10 02;7(10):e14120.
PMID: 31579026 DOI: 10.2196/14120

BACKGROUND: Wrist-worn activity trackers are popular, and an increasing number of these devices are equipped with heart rate (HR) measurement capabilities. However, the validity of HR data obtained from such trackers has not been thoroughly assessed outside the laboratory setting.
OBJECTIVE: This study aimed to investigate the validity of HR measures of a high-cost consumer-based tracker (Polar A370) and a low-cost tracker (Tempo HR) in the laboratory and free-living settings.
METHODS: Participants underwent a laboratory-based cycling protocol while wearing the two trackers and the chest-strapped Polar H10, which acted as criterion. Participants also wore the devices throughout the waking hours of the following day during which they were required to conduct at least one 10-min bout of moderate-to-vigorous physical activity (MVPA) to ensure variability in the HR signal. We extracted 10-second values from all devices and time-matched HR data from the trackers with those from the Polar H10. We calculated intraclass correlation coefficients (ICCs), mean absolute errors, and mean absolute percentage errors (MAPEs) between the criterion and the trackers. We constructed decile plots that compared HR data from Tempo HR and Polar A370 with criterion measures across intensity deciles. We investigated how many HR data points within the MVPA zone (≥64% of maximum HR) were detected by the trackers.
RESULTS: Of the 57 people screened, 55 joined the study (mean age 30.5 [SD 9.8] years). Tempo HR showed moderate agreement and large errors (laboratory: ICC 0.51 and MAPE 13.00%; free-living: ICC 0.71 and MAPE 10.20%). Polar A370 showed moderate-to-strong agreement and small errors (laboratory: ICC 0.73 and MAPE 6.40%; free-living: ICC 0.83 and MAPE 7.10%). Decile plots indicated increasing differences between Tempo HR and the criterion as HRs increased. Such trend was less pronounced when considering the Polar A370 HR data. Tempo HR identified 62.13% (1872/3013) and 54.27% (5717/10,535) of all MVPA time points in the laboratory phase and free-living phase, respectively. Polar A370 detected 81.09% (2273/2803) and 83.55% (9323/11,158) of all MVPA time points in the laboratory phase and free-living phase, respectively.
CONCLUSIONS: HR data from the examined wrist-worn trackers were reasonably accurate in both the settings, with the Polar A370 showing stronger agreement with the Polar H10 and smaller errors. Inaccuracies increased with increasing HRs; this was pronounced for Tempo HR.

Matched MeSH terms: Accelerometry/instrumentation; Accelerometry/standards; Accelerometry/statistics & numerical data
Fulltext Angular velocity and elevation angle: the proposed human model scalable tracking model using linear regression

Yong CY, Sudirman R, Chew KM

Sains Malaysiana, 2015;44(12):1661-1669.

A scalable tracking human model was proposed for recognizing human jogging and walking activities. The model aims to detect and track a particular subject by using wearable sensor. Data collected are in accelerometer readings in three axes and gyroscope readings in three axes. The development of proposed human model is based on the moderating effects on human movements. Two moderators were proposed as the moderating factors of human motion and they are angular velocity and elevation angle. Linear regression is used to investigate the relationship among inputs, moderators and outputs of the model. The result of this study showed that the angular velocity and elevation angle moderators are affecting the relation of research output. Acceleration in x-axis (Ax) and angular velocity in y-axis (Gy) are the two main components in directing
a motion. Classification between jogging and walking motions was done by measuring the magnitude of angular velocity and elevation angle. Jogging motion was classified and identified with larger angular velocity and elevation angle. The two proposed hypotheses were supported and proved by research output. The result is expected to be beneficial and able to assist researcher in investigating human motions.

Matched MeSH terms: Accelerometry
Fulltext Minimal Agreement between Internal and External Training Load Metrics across a 2-wk Training Microcycle in Elite Squash

James C, Dhawan A, Jones T, Pok C, Yeo V, Girard O

J Sports Sci Med, 2021 03;20(1):101-109.
PMID: 33707993 DOI: 10.52082/jssm.2021.101

This study investigated the relationships between internal and external training load metrics across a 2-week 'in-season' microcycle in squash. 134 on-court and 32 off-court 'conditioning' sessions were completed by fifteen elite squash players with an average (±SD) of 11 ± 3 per player. During every session, external load was captured using a tri-axial accelerometer to calculate Playerload; i.e., the instantaneous rate of change of acceleration across 3-dimensional planes. Internal load was measured using heart rate (HR), global (sRPE) and differential RPE (dRPE-Legs, dRPE-Breathing). Additionally, HR was used to calculate Banister's, Edward's and TEAM TRIMPs. Across 166 training sessions, Playerload was moderately correlated with TRIMP-Banister (r = 0.43 [95% CI: 0.29-0.55], p < 0.001) and TRIMP-Edwards (r = 0.50 [0.37-0.61], p < 0.001). Association of Playerload with TRIMP-TEAM (r = 0.24 [0.09-0.38], p = 0.001) was small. There was a moderate correlation between sRPE and Playerload (r = 0.46 [0.33-0.57], p < 0.001). Association of sRPE was large with TRIMP-Banister (r = 0.68 [0.59-0.76], p = 0.001), very large with TRIMP-Edwards (r = 0.79 [0.72-0.84], p < 0.001) and moderate with TRIMP-TEAM (r = 0.44 [0.31-0.56], p < 0.001). Both dRPE-Legs (r = 0.95 [0.93-0.96], p < 0.001) and dRPE-Breathing (r = 0.92 [0.89-0.94], p < 0.001) demonstrated nearly perfect correlations with sRPE and with each other (r = 0.91 [0.88-0.93], p < 0.001). Collection of both internal and external training load data is recommended to fully appreciate the physical demands of squash training. During a training microcycle containing a variety of training sessions, interpreting internal or external metrics in isolation may underestimate or overestimate the training stress a player is experiencing.

Matched MeSH terms: Accelerometry
Fulltext Accelerometer-measured physical activity and its relationship with body mass index (BMI) and waist circumference (WC) measurements: a cross-sectional study on Malaysian adults

Lee, Yi Yi, Narimah Samat, Wan Manan Wan Muda

Malays J Nutr, 2017;23(3):397-408.
MyJurnal

Introduction: Physical activity has been shown to be beneficial for the prevention of
obesity and non-communicable diseases. Our contemporary way of life that is technology
dependent has significantly reduced physical activity. This study aimed to determine
accelerometer-measured physical activity (moderate-to-vigorous physical activity (MVPA))
among adults in high and low walkability neighbourhoods in Penang and Kota Bharu,
Malaysia.

Methods: Participants (n=490) were sampled using multistage sampling method
from neighbourhoods with varied levels of walkability using Geographical Information
System (GIS). Physical activity was measured objectively using Actigraph GT3X+
accelerometers, worn by the participants on their waists for a period of 5 to 7 days.

Results:
The participants had a mean of 13.5 min/day of MVPA. Total MVPA was significantly
higher among participants in high walkability neighbourhoods (19.7 min/day vs. 9.1 min/
day). Results from t-test showed that the time spent on MVPA per day was significantly
lower among participants residing in low walkability neighbourhoods. The final model
of the MIXED model statistical tests showed that total MVPA was significantly associated
with BMI, but not with WC measurements, after adjusting for covariates.

Conclusion: Most
of the participants had very low MVPA and did not achieve the current physical activity
recommendations, implying that Malaysian adults residing in these two cities were not
physically active to achieve health benefits. Results are suggestive of the importance of the
walkability concept in neighbourhoods in encouraging physical activity and healthy body
weight among Malaysians.

Matched MeSH terms: Accelerometry
Jumping in the Night: An Investigation of the Leaping Activity of the Western Tarsier (Cephalopachus bancanus borneanus) Using Accelerometers

Costantini D, Sebastiano M, Goossens B, Stark DJ

Folia Primatol., 2017;88(1):46-56.
PMID: 28662508 DOI: 10.1159/000477540

Accelerometers enable scientists to quantify the activity of free-living animals whose direct observation is difficult or demanding due to their elusive nature or nocturnal habits. However, the deployment of accelerometers on small-bodied animals and, in particular, on primates has been little explored. Here we show the first application of accelerometers on the western tarsier (Cephalopachus bancanus borneanus), a nocturnal, small-bodied primate endemic to the forests of Borneo. The fieldwork was carried out in the Lower Kinabatangan Wildlife Sanctuary, Sabah, Malaysian Borneo. We provide guidelines for the deployment of accelerometers on tarsiers that might also be applied to other primate species. Our collected data on 2 females show levels of leaping activity comparable to those previously described using direct observation of wild or captive individuals. The 2 females showed different patterns of leaping activity, which calls for work to explore individual differences further. Our work demonstrates that accelerometers can be deployed on small primates to acquire body motion data that would otherwise be demanding to collect using classic field observations. Future work will be focused on using accelerometer data to discriminate in more detail the different behaviours tarsiers can display and to address the causes and consequences of individual variations in activity.

Matched MeSH terms: Accelerometry
Sputtered Encapsulation as Wafer Level Packaging for Isolatable MEMS Devices: A Technique Demonstrated on a Capacitive Accelerometer

Hamzah AA, Yunas J, Majlis BY, Ahmad I

Sensors (Basel), 2008 Nov 19;8(11):7438-7452.
PMID: 27873938

This paper discusses sputtered silicon encapsulation as a wafer level packaging approach for isolatable MEMS devices. Devices such as accelerometers, RF switches, inductors, and filters that do not require interaction with the surroundings to function, could thus be fully encapsulated at the wafer level after fabrication. A MEMSTech 50g capacitive accelerometer was used to demonstrate a sputtered encapsulation technique. Encapsulation with a very uniform surface profile was achieved using spin-on glass (SOG) as a sacrificial layer, SU-8 as base layer, RF sputtered silicon as main structural layer, eutectic gold-silicon as seal layer, and liquid crystal polymer (LCP) as outer encapsulant layer. SEM inspection and capacitance test indicated that the movable elements were released after encapsulation. Nanoindentation test confirmed that the encapsulated device is sufficiently robust to withstand a transfer molding process. Thus, an encapsulation technique that is robust, CMOS compatible, and economical has been successfully developed for packaging isolatable MEMS devices at the wafer level.

Matched MeSH terms: Accelerometry
Fulltext A smart wheelchair prototype based on hand gesture control

Shaari AR, Mohd Jani MN, Mohamed Yunus AS

Journal of Engineering and Science Research, 2017;1(2):209-214.
MyJurnal

Wheelchair has been an important assistive device and the demand are ever rising because of the increasing physically handicapped and old age populations. The recent development in the robotics artificial intelligence extends vast scope for developing the more advanced and intelligent one to overcome limitations of the existing traditional wheelchairs. The prototype smart wheelchair were present on this paper using hardware implementation with the help of simple hand gesture which is comprises of an accelerometer mounted on the hand glove senses the tilt angle of the user hand movements and transmits control signal to the receiver mounted on wheelchair. This will interpret the movement accordingly required by user. The wheelchair control unit is developed by integration of ATMEGA328 microcontroller with Arduino UNO. The wheelchair is developed to allow peoples to move safely and put reliability in accomplishment of some important tasks in daily life.

Matched MeSH terms: Accelerometry
Fulltext Accelerometer-measured 24-hour movement behaviours over 7 days in Malaysian children and adolescents: A cross-sectional study

Brady SM, Salway R, Mariapun J, Millard L, Ramadas A, Rizal H, et al.

PLoS One, 2024;19(2):e0297102.
PMID: 38377079 DOI: 10.1371/journal.pone.0297102

BACKGROUND: Quantifying movement behaviours over 24-hours enables the combined effects of and inter-relations between sleep, sedentary time and physical activity (PA) to be understood. This is the first study describing 24-hour movement behaviours in school-aged children and adolescents in South-East Asia. Further aims were to investigate between-participant differences in movement behaviours by demographic characteristics and timing of data collection during Ramadan and COVID-19 restrictions.
METHODS: Data came from the South-East Asia Community Observatory health surveillance cohort, 2021-2022. Children aged 7-18 years within selected households in Segamat, Malaysia wore an Axivity AX6 accelerometer on their wrist for 24 hours/day over 7 days, completed the PAQ-C questionnaire, and demographic information was obtained. Accelerometer data was processed using GGIR to determine time spent asleep, inactive, in light-intensity PA (LPA) and moderate-to-vigorous PA (MVPA). Differences in accelerometer-measured PA by demographic characteristics (sex, age, ethnicity, socioeconomic group) were explored using univariate linear regression. Differences between data collected during vs outside Ramadan or during vs after COVID-19 restrictions, were investigated through univariate and multiple linear regressions, adjusted for age, sex and ethnicity.
RESULTS: The 491 participants providing accelerometer data spent 8.2 (95% confidence interval (CI) = 7.9-8.4) hours/day asleep, 12.4 (95% CI = 12.2-12.7) hours/day inactive, 2.8 (95% CI = 2.7-2.9) hours/day in LPA, and 33.0 (95% CI = 31.0-35.1) minutes/day in MVPA. Greater PA and less time inactive were observed in boys vs girls, children vs adolescents, Indian and Chinese vs Malay children and higher income vs lower income households. Data collection during Ramadan or during COVID-19 restrictions were not associated with MVPA engagement after adjustment for demographic characteristics.
CONCLUSIONS: Demographic characteristics remained the strongest correlates of accelerometer-measured 24-hour movement behaviours in Malaysian children and adolescents. Future studies should seek to understand why predominantly girls, adolescents and children from Malay ethnicities have particularly low movement behaviours within Malaysia.

Matched MeSH terms: Accelerometry
Development of a control system for artificially rehabilitated limbs: a review

Bhuiyan MS, Choudhury IA, Dahari M

Biol Cybern, 2015 Apr;109(2):141-62.
PMID: 25491411 DOI: 10.1007/s00422-014-0635-1

Development of an advanced control system for prostheses (artificial limbs) is necessary to provide functionality, effectiveness, and preferably the feeling of a sound living limb. The development of the control system has introduced varieties of control strategies depending on the application. This paper reviews some control systems used for prosthetics, orthotics, and exoskeletons. The advantages and limitations of different control systems for particular applications have been discussed and presented in a comparative manner to help in deciding the appropriate method for pertinent application.

Matched MeSH terms: Accelerometry/instrumentation
Mechanomyography and muscle function assessment: a review of current state and prospects

Ibitoye MO, Hamzaid NA, Zuniga JM, Abdul Wahab AK

Clin Biomech (Bristol, Avon), 2014 Jun;29(6):691-704.
PMID: 24856875 DOI: 10.1016/j.clinbiomech.2014.04.003

Previous studies have explored to saturation the efficacy of the conventional signal (such as electromyogram) for muscle function assessment and found its clinical impact limited. Increasing demand for reliable muscle function assessment modalities continues to prompt further investigation into other complementary alternatives. Application of mechanomyographic signal to quantify muscle performance has been proposed due to its inherent mechanical nature and ability to assess muscle function non-invasively while preserving muscular neurophysiologic information. Mechanomyogram is gaining accelerated applications in evaluating the properties of muscle under voluntary and evoked muscle contraction with prospects in clinical practices. As a complementary modality and the mechanical counterpart to electromyogram; mechanomyogram has gained significant acceptance in analysis of isometric and dynamic muscle actions. Substantial studies have also documented the effectiveness of mechanomyographic signal to assess muscle performance but none involved comprehensive appraisal of the state of the art applications with highlights on the future prospect and potential integration into the clinical practices. Motivated by the dearth of such critical review, we assessed the literature to investigate its principle of acquisition, current applications, challenges and future directions. Based on our findings, the importance of rigorous scientific and clinical validation of the signal is highlighted. It is also evident that as a robust complement to electromyogram, mechanomyographic signal may possess unprecedented potentials and further investigation will be enlightening.

Matched MeSH terms: Accelerometry/instrumentation
Accelerometer Profile of Physical Activity and Sedentary Behavior in a Multi-Ethnic Urban Asian Population

Chu AHY, Bernard JY, Koh D, Müller-Riemenschneider F

Res Q Exerc Sport, 2021 Sep;92(3):361-368.
PMID: 32154777 DOI: 10.1080/02701367.2020.1734520

Purpose: Variability in accelerometry-data processing decisions limited data comparability across studies. We aimed to examine different accelerometry-data processing rules: varying bout lengths and allowance of 0- and 2-min interruptions on the total and bout-accumulated time spent in moderate-to-vigorous physical activity (MVPA) and sedentary behavior estimates, and describe the distribution of activity time based on counts per min (CPM) in granular categories. Method: Using the Singapore Health 2 survey, this study included 746 adults (41.8% women, median age 45.0 years) who provided valid ActiGraph GT3X+ accelerometer-data (≥4 valid days with ≥10-h/day). Quantile regression analysis adjusting for accelerometry daily wear time, age, and gender was performed to calculate the median and interquartile range of accelerometry estimates. Results: Median MVPA time accumulated in bouts of 1-min versus bouts of 10-min was 39.2 min/day and 6.0 min/day, respectively. MVPA time was higher when considering a 2-min interruption (range: 1.8-39.2 min/day) compared to 0-min interruption (range: 0-35.5 min/day) across bout lengths of 1- to 15-min. Participants were sedentary (≤100 CPM) for a daily median of 7.6 h/day. Median activities min/day on the lower-intensity activity spectrum (100-2499 CPM) decreased from 63.4 to 4.6 min/day, while on the higher-intensity activity spectrum (≥2500 CPM) was ≤2.9 min/day. Men generally spent more time in MVPA than women. Conclusions: This study highlights the differences in accelerometry estimates based on data processing decisions, and the importance of quantifying accelerometry-based activity time across the granular intensity spectrum. More studies are warranted to understand the determinants and health impact of these behaviors.

Matched MeSH terms: Accelerometry/methods*
Measuring the Daily Activity of Lying Down, Sitting, Standing and Stepping of Obese Children Using the ActivPALTM Activity Monitor

Wafa SW, Aziz NN, Shahril MR, Halib H, Rahim M, Janssen X

J Trop Pediatr, 2017 04 01;63(2):98-103.
PMID: 27539845 DOI: 10.1093/tropej/fmw052

This study describes the patterns of objectively measured sitting, standing and stepping in obese children using the activPALTM and highlights possible differences in sedentary levels and patterns during weekdays and weekends. Sixty-five obese children, aged 9-11 years, were recruited from primary schools in Terengganu, Malaysia. Sitting, standing and stepping were objectively measured using an activPALTM accelerometer over a period of 4-7 days. Obese children spent an average of 69.6% of their day sitting/lying, 19.1% standing and 11.3% stepping. Weekdays and weekends differed significantly in total time spent sitting/lying, standing, stepping, step count, number of sedentary bouts and length of sedentary bouts (p < 0.05, respectively). Obese children spent a large proportion of their time sedentarily, and they spent more time sedentarily during weekends compared with weekdays. This study on sedentary behaviour patterns presents valuable information for designing and implementing strategies to decrease sedentary time among obese children, particularly during weekends.

Matched MeSH terms: Accelerometry/instrumentation*
Physical activity, but not sedentary time, influences bone strength in late adolescence

Tan VP, Macdonald HM, Gabel L, McKay HA

Arch Osteoporos, 2018 Mar 20;13(1):31.
PMID: 29556801 DOI: 10.1007/s11657-018-0441-9

Physical activity is essential for optimal bone strength accrual, but we know little about interactions between physical activity, sedentary time, and bone outcomes in older adolescents. Physical activity (by accelerometer and self-report) positively predicted bone strength and the distal and midshaft tibia in 15-year-old boys and girls. Lean body mass mediated the relationship between physical activity and bone strength in adolescents.
PURPOSE: To examine the influence of physical activity (PA) and sedentary time on bone strength, structure, and density in older adolescents.
METHODS: We used peripheral quantitative computed tomography to estimate bone strength at the distal tibia (8% site; bone strength index, BSI) and tibial midshaft (50% site; polar strength strain index, SSIp) in adolescent boys (n = 86; 15.3 ± 0.4 years) and girls (n = 106; 15.3 ± 0.4 years). Using accelerometers (GT1M, Actigraph), we measured moderate-to-vigorous PA (MVPAAccel), vigorous PA (VPAAccel), and sedentary time in addition to self-reported MVPA (MVPAPAQ-A) and impact PA (ImpactPAPAQ-A). We examined relations between PA and sedentary time and bone outcomes, adjusting for ethnicity, maturity, tibial length, and total body lean mass.
RESULTS: At the distal tibia, MVPAAccel and VPAAccel positively predicted BSI (explained 6-7% of the variance, p

Matched MeSH terms: Accelerometry/methods
Estimation of vertical ground reaction force during running using neural network model and uniaxial accelerometer

Ngoh KJ, Gouwanda D, Gopalai AA, Chong YZ

J Biomech, 2018 07 25;76:269-273.
PMID: 29945786 DOI: 10.1016/j.jbiomech.2018.06.006

Wearable technology has been viewed as one of the plausible alternatives to capture human motion in an unconstrained environment, especially during running. However, existing methods require kinematic and kinetic measurements of human body segments and can be complicated. This paper investigates the use of neural network model (NN) and accelerometer to estimate vertical ground reaction force (VGRF). An experimental study was conducted to collect sufficient samples for training, validation and testing. The estimated results were compared with VGRF measured using an instrumented treadmill. The estimates yielded an average root mean square error of less than 0.017 of the body weight (BW) and a cross-correlation coefficient greater than 0.99. The results also demonstrated that NN could estimate impact force and active force with average errors ranging between 0.10 and 0.18 of BW at different running speeds. Using NN and uniaxial accelerometer can (1) simplify the estimation of VGRF, (2) reduce the computational requirement and (3) reduce the necessity of multiple wearable sensors to obtain relevant parameters.

Matched MeSH terms: Accelerometry

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