Earticle

고령인구의 증가가 사회적 문제로 부상하면서 고령자 상황인지 및 응급상황 대응 기술에 대한 수요가 증가하고 있다. 낙상은 고령자의 일상생활에서 빈번히 발생하는 동시에 고령자의 건강과 삶의 질을 위협하는 중대한 위험요인이므로 이에 대한 대비가 중요하다. 보폭 및 보행 속도 측정과 같은 보행 분석은 낙상 가능성을 감지하는 데 중요한 인자로 알려져 있다. 본 연구에서는 저가의 가속도 센서만을 이용하여 보행속도를 측정하는 방법을 제안한다. 실험을 통해 측정 데이터와 실제 보행속도에 따른 오차 경향을 분석함으로써 일상 생활 중 보행 분석이 가능함을 확인하였다.

본 연구의 목적은 요양보호사의 신체활동을 우선 정량적으로 측정하고, 이후 연구의 목적 달성을 위해 가속도계 분석과 해석주의에 기반한 질적연구를 결합한 혼합연구(mixed methods research)를 수행하였다. 이는 혼합연구의 철학적 전통 중 포섭(nesting) 설계에 해당한다. 그 결과를 바탕으로 사회생태학적 모델이 제시하는 다층적 수준의 개입 방향을 탐색하고자 하였다. 1차 연구에서는 26명의 요양보호사가 가속도계를 착용하여 연구에 참여하였으며, 이를 통해 신체활동량과 신체활동 패턴을 객관적으로 측정하였다. 2차 연구에서는 해석주의에 기반한 질적연구를 통해 근무환경과 신체활동 간의 상호작용을 탐색한 결과, 세 가지 주요 주제가 도출되었다. 1) 제한된 건강 개념과 실천 인식, 2) 신체활동 실천의 구조적 제약, 3) 신체활동 참여의 동기 결여가 이에 해당한다. 이러한 결과를 통해 요양보호사의 신체활동을 양적 및 질적 측면에서 통합적으로 분석하였으며, 본 연구는 향후 요양보호사의 건강증진과 사회적 지지체계 구축을 위한 기초자료로 활용될 수 있을 것으로 기대한다.

Objectives The purpose of this study was to quantitatively assess the physical activity of caregivers and to examine the factors influencing their physical activity using a mixed-method approach that integrated accelerometer-based analysis with qualitative research grounded in interpretivism. Methods This study adopted a mixed-method design with a nesting approach within the philosophical traditions of mixed-method research. The socio-ecological model was used as a conceptual framework to explore potential intervention strategies. In the first phase, 26 caregivers participated in accelerometer-based data collection to objectively measure physical activity levels and patterns. In the second phase, a qualitative study informed by interpretivism was conducted to explore the interaction between caregivers’ work environments and their physical activity behaviors. Results Three main themes emerged from the qualitative analysis: 1) limited conceptions of health and its practice, 2) structural constraints on participation in physical activity, and 3) lack of motivation to engage in physical activity. The integrated analysis of quantitative and qualitative findings provided a comprehensive understanding of caregivers’ physical activity patterns and the contextual factors influencing their engagement in health-promoting physical activity. Conclusions The findings offer important insights into the physical activity behaviors of caregivers from both quantitative and qualitative perspectives. These results provide foundational evidence for developing strategies and supportive social systems aimed at promoting the health and well-being of caregivers.

본 논문은 스마트폰을 이용하여 장시간동안 연속적으로 사용자의 행동정보를 수집 및 기록하는데 있어 요구되는 최적화된 수집주기를 제안한다. 스마트폰에서 장시간 기록을 하려면 배터리소모, 데이터 크기의 증가, 그리고 고성능 컴퓨팅의 요구와 같은 문제점을 고려해야 하며, 이러한 문제점은 수집주기를 최적화함으로써 해결가능하다. 본 논문에서는, 적절한 정확도를 유지하는 최적화된 수집주기를 제안하기 위해 실제 일상생활에서 스마트폰을 이용하여 사용자의 행동을 수집하고 기록하는 실험을 진행하였다. 실험결과 앉기의 경우 32초, 걷기와 서기의 경우 8초의 수집주기 내에서 약 80% 이상의 분류 정확성을 보이고 있음을 확인하였다. 결론적으로 앉기, 걷기, 서기와 같은 정도의 사용자의 행동을 일상생활에서 기록하기 위한 최적의 수집주기는 8초로 고려된다. 이러한 결론은 스마트폰을 이용한 디지털 문진표에 사용될 수 있다.

In this paper, we propose optimized data collection cycle required for long-term and continues collecting and recording of user’s activity information in smartphone environment. For long-term recording in smartphones, we face 3 problems such as battery durability, data length, and computing power. These problems can be solved by optimizing data collection cycle. To propose optimal data collection cycle while maintaining required accuracy, we conduct experiments by collecting and recording daily activity of a user through a smartphone. The experimental results show that activity classification accuracy is maintained above 80% within 32 second-cycle for sitting and 8 second-cycle for walking and standing. As a result, we can conclude optimal data collection cycle for activity recording is 8 seconds. This conclusion can be used the mobile health screening form.

Objective: To investigate whether accelerometer-derived metrics from an upper-limb reaching task can discriminate between normal and intentionally tremulous movements in healthy adults and to examine the influence of low-pass filtering on tremor sensitivity. Design: Experimental repeated-measures study Methods: Nineteen healthy adults (19-35 years old) performed a seated reaching task from a standardized starting position to targets at 120% arm length at eye and shoulder heights. A wireless triaxial accelerometer was secured to the dorsum of the hand, recording signals at 1,500 Hz and synchronized with a footswitch to define movement onset and offset. Participants completed three trials of normal and intentional tremor movements at both heights. Acceleration data were low-pass filtered using a 4th-order Butterworth filter (cutoffs of 5 and 10 Hz). The movement time, peak-to-peak count of jerk magnitude, mean jerk in each axis, and jerk cost were computed and compared between conditions using paired t-tests. Results: With 5 Hz filtering, intentional tremor produced significantly longer movement times, higher peak-to-peak counts, and elevated jerk cost at both heights (all p < 0.001), whereas mean axis-specific jerk values were largely non-discriminative. Increasing the cutoff to 10 Hz increased the absolute peak counts while preserving between-condition differences (p < 0.001 for all comparisons). Conclusions: Peak-to-peak count and jerk cost derived from accelerometer-based jerk magnitude sensitively distinguished normal from intentional tremor during a reaching task and were robust to modest filtering changes. These metrics show promise as quantitative digital biomarkers for upper limb tremor assessment in future clinical populations.

Many wearable devices include PPG (photoplethysmography) sensors for non-invasive heart rate monitoring. However, PPG signals are heavily corrupted by motion interference, and rely on simultaneous motion measurements to remove the interference. Accelerometers are used commonly, but cannot differentiate between acceleration due to movement and acceleration due to gravity. This paper compares measurements of motion using accelerometers and gyroscopes to give a more complete estimate of wrist motion. Results show the two sensor signals are very different, with low correlations present. When used in a wrist PPG heart rate algorithm gyroscope motion estimates obtain better performance in half of the cases.

To improve the shock-resistance of piezoresistive high-g accelerometer, we propose a design of piezoresistive high-g accelerometer. The accelerometer employs special-shaped proof masses system with a cross gap. Four tiny sensing beams are bonded above the cross gap. The expression of the deformation, natural frequency and damping is deduced, and the structural parameters are optimized. The accelerometer structure is simulated and verified by finite element method (FEM) simulation. The results show that the range of the accelerometer can reach 200,000 g, the natural frequency is 453.6 kHz, and the cross-axis sensitivity of X-axis and Y-axis is 0.25% and 0.11%, respectively, which can apply to the measurement of high shock. Contrastively, the cross-axis sensitivity of X-axis and Y-axis is respectively, reduced by 93.2% and 96.9%. The sensitivity of our accelerometer is 0.88 μV/g. It is of great value for the application of piezoresistive high-g accelerometer with high shock-resistance.

Mobile authentication/identification has grown into a priority issue nowadays because of its existing outdated mechanisms, such as PINs or passwords. In this paper, we introduce gait recognition by using a mobile accelerometer as not only effective but also as an implicit identification model. Unlike previous works, the gait recognition only performs well with a particular mobile specification (e.g., a fixed sampling rate). Our work focuses on constructing a unique adaptive mechanism that could be independently deployed with the specification of mobile devices. To do this, the impact of the sampling rate on the preprocessing steps, such as noise elimination, data segmentation, and feature extraction, is examined in depth. Moreover, the degrees of agreement between the gait features that were extracted from two different mobiles, including both the Average Error Rate (AER) and Intra-class Correlation Coefficients (ICC), are assessed to evaluate the possibility of constructing a device-independent mechanism. We achieved the classification accuracy approximately $91.33{\pm}0.67%$ for both devices, which showed that it is feasible and reliable to construct adaptive cross-device gait recognition on a mobile phone.

Horse breeders suffer massive economic losses due to dystocia, abortion, and stillbirths. In Thoroughbred mares, breeders often miss the foaling process because approximately 86% of the foaling events occur from 19:00 to 7:00; consequently, breeders cannot assist mares experiencing dystocia. To solve this problem, various foaling alarm systems have been developed. However, there is a need to develop a new system to overcome the shortcomings of the existing devices and improve their accuracy. To this end, the present study aimed to (1) develop a novel foaling alarm system and (2) compare its accuracy with that of the existing Foalert™ system. Specifically, eighteen Thoroughbred mares (11.9 ± 4.0 years old) were included. An accelerometer was used to analyze specific foaling behaviors. Behavioral data were transmitted to a data server every second. Depending on the acceleration value, behaviors were automatically classified by the server as categorized behaviors 1 (behaviors without change in body rotation), 2 (behaviors with sudden change in body rotation, such as rolling over), and 3 (behaviors with long-term change in body rotation, such as lying down laterally). The system was designed to alarm when the duration of categorized behaviors 2 and 3 was 12.9% and that of categorized behavior 3 was 1% during 10 min. The system measured the duration of each categorized behavior every 10 min and transmitted an alarm to the breeders when foaling was detected. To confirm its accuracy, the foaling detection time of the novel system was compared with that of Foalert™. The novel foaling alarm system and Foalert™ alarmed foaling onset respectively 32.6 ± 17.9 and 8.6 ± 1.0 min prior to foal discharge, and the foaling detection rate of both systems was 94.4%. Therefore, the novel foaling alarm system equipped with an accelerometer can precisely detect and alert foaling onset.

The purpose of this study was to determine the reliability and validity of the postural balance program which uses the movement accelerating field principles of posture balance training and evaluation equipment and smartphone movement accelerometer program (SMAP) in healthy young adults. A total of 34 people were appointed as the subject among the healthy young adults. By using Biodex stability system (BSS) and SMAP on the subject, the posture balance capability was evaluated. For the test-retest reliability, SMAP showed the intra-class correlation (ICC: .62~.91) and standard error measurement (SEM: .01~.08). BSS showed the moderate to high reliability of ICC (.88~.93) and SEM (.02~.20). In the reliability of inter-rater, ICC (.59~.73) as to SMAP, showed the reliability of moderate in eyes open stability all (EOSA), eyes open stability anterior posterior (EOSAP), eyes open stability medial lateral (EOSML) and eyes open dinamic all (EODA), eyes open danamic anterior posterior (EODAP), and eyes open danamic medial lateral (EODML). However, ICC showed reliability which was as low as .59 less than in other movements. In addition, BSS showed the reliability of high as ICC (.70~.75). It showed reliability which was as low as ICC (.59 less than) in other movements. In correlation to the balance by attitudes between SMAP and BSS, EOSML (r=.62), EODA (r=.75), EODML (r=.72), ECDAP (r=.64), and ECDML (r=.69) shown differ significantly (p<.05). However, the correlation noted in other movements did not differ significantly. Therefore, SMAP and BSS can be usefully used in the posture balance assessment of the static and dynamic condition with eyes opened and closed.

Purpose: Driving a car is an essential component of daily life. For safe driving, each driver must perceive sensory information and respond rapidly and accurately. Brake response time (BRT) is a particularly important factor in the total stopping distance of a vehicle, and therefore is an important factor in traffic accident prevention research. The purpose of the current study was (1) to compare accelerometer. BRTs analyzed by three different methods and (2) to investigate possible correlations between accelerometer-BRTs and foot switch-BRTs, which are measured method using a foot switch. Methods: Eighteen healthy subjects participated in this study. BRT was measured with either a tri-axial accelerometer or a footswitch. BRT with a tri-axial accelerometer was analyzed using three methods: maximum acceleration time, geometrical center, and center of maximum and minimum acceleration values. Results: Both foot switch-BRTs and accelerometer-BRTs were delayed. ANOVA for accelerometer BRTs yielded significant main effects for axis and analysis, while the interaction effect between axis and analysis was not significant. Calculating the Pearson correlation between accelerometer-BRT and foot switch-BRT, we found that maximum acceleration time and center of maximum and minimum acceleration values were significantly correlated with foot switch-BRT (p<0.05). The X axis of the geometrical center was significantly correlated with foot switch-BRTs (p<0.05), but Y and Z axes were not (p>0.05). Conclusion: These findings suggest that the maximum acceleration time and the center of maximum and minimum acceleration value are significantly correlated with foot switch-BRTs.

Background: Posture balance control is the ability to maintain the body's center of gravity in the minimal postural sway state on a supportive surface. This ability is obtained through a complicated process of sensing the movements of the human body through sensory organs and then integrating the information into the central nervous system and reacting to the musculoskeletal system and the support action of the musculoskeletal system. Motor function, including coordination, motor, and vision, vestibular sense, and sensory function, including proprioception, should act in an integrated way. However, more than half of stroke patients have motor, sensory, cognitive, and emotional disorders for a long time. Motor and sensory disorders cause the greatest difficulty in postural control among stroke patients. Objects: The purpose of this study is to determine the effect of visual and somatosensory information on postural sway in stroke patients and carrying out a kinematic analysis using a tri-axial accelerometer and a quantitative assessment. Methods: Thirty-four subjects posed four stance condition was accepted various sensory information for counterbalance. This experiment referred to the computerized dynamic posturography assessments and was redesigned four condition blocking visual and somatosensory information. To measure the postural sway of the subjects' trunk, a wireless tri-axial accelerometer was used by signal vector magnitude value. Ony-way measure analysis of variance was performed among four condition. Results: There were significant differences when somatosensory information input blocked (p<.05). Conclusion: The sensory significantly affecting the balance ability of stroke patients is somatosensory, and the amount of actual movement of the trunk could be objectively compared and analyzed through quantitative figures using a tri-axial accelerometer for balance ability.

Epoch in accelerometer measurements is an important option that af-fects the results of physical activity (PA) analysis. Many studies have been conducted to investigate the effect of epoch on PA output in ado-lescents, but few have been performed on highly active youth athletes. We aimed to examine the differences in energy expenditure and time spent in different activity intensities by applying various epoch lengths in adolescent athletes. The participants of this study comprised 31 male athletes aged 12 to 13 in basketball, soccer, and taekwondo teams. Ath-letes wore a tri-axial accelerometer attached to the right hip for 6 to 7 consecutive days, including sleeping time. Subsequently, the recorded data from the accelerometer were downloaded using the ActiLife soft-ware and analyzed by varying the epoch to 1, 10, 30, and 60 sec. Daily average metabolic equivalents (METs) increased as the epoch in-creased (F=2.918, P=0.037), showing a significant difference between 1 and 60-sec epochs. As epoch length increased, sedentary (0–1.5 METs) (F=94.001, P=0.000) and high intensity (6 METs and higher) activity time (F=3.536, P=0.017) decreased, while low (1.5–3 METs) (F=173.949, P= 0.000), moderate (3–6 METs) (F=70.792, P=0.000), and moderate-to-vig-orous activity (3 METs and higher intensity) (F=34.683, P=0.000) times increased. Comparing PA among adolescent athletes by varying epoch settings of accelerometers revealed differences in PA levels and time spent in different activity intensities. Future studies should consider the characteristic changes in the PA outputs according to the epoch length in very active adolescent athletes.

The purpose of this study was to determine the reliability and suitability of accelerometer measurements on gait asymmetry and balance in stroke patients. This literature review uses accelerometers to search for static and dynamic balance and gait asymmetry in adults diagnosed with stroke and to refer to the 2018 paper from 2008. The results of the compilation of the paper were as follows. The balance of the accelerometers showed measurements similar to those of the previous BBS and TUG. In other words, using the accelerometer to measure the balance suggests that it can be clinically useful. Next, studies that analyzed the gait asymmetry of accelerometers indicated that the algorithm's limits for estimating time were insufficient, but that the reliability tool for measuring the gait asymmetry was proven. This result shows that it is possible to analyze walking patterns through an accelerometer in individuals with hemiparetic stroke.

Objective: The aim of this study is to evaluate the acceleration of the center of mass (COM) of the body in stroke patients. Method: Seventeen stroke patients and 9 normal subjects were participated. Three dimensional gait analysis was used to classify gait phases for the reference. The accelerometer held over the COM were used to record vertical and medio- lateral accelerations of the COM of the body. Modified Ashworth scale and Brunnstrom stage were used to evaluate the clinical status of stroke patients. Results: In normal subjects, the acceleration showed symmetric pattern. The maximum peak of vertical acceleration occurred in loading response. In stroke patients, the acceleration wave was characterized by asymmetry and polyphasicity. Maximum peak in affected side was higher than that in unaffected side (p＜0.05). There were significant correlations between several elements of hemiplegic gait and the correspondent acceleration values; interval of successive peak I in vertical acceleration vs. step time, walking velocity and swing symmetry ratio vs. mean peak I, swing symmetry ratio vs. affected side peak I, step length symmetry ratio vs. peak I symmetry ratio. Conclusion: The accelerometer can be an easy and useful way to evaluate gait characteristics in stroke patients. (J Korean Acad Rehab Med 2004; 28: 488-493)

목적: 본 연구는 뇌졸중 환자를 대상으로 사용한 가속도계 연구를 고찰하여 뇌졸중 환자의 일상생활활동평가 도구로 가속도계가 유용하게 활용될 수 있는 지 알아보고자 하였다. 연구방법: 2014년 2월부터 3월까지 PubMed, EMBASE, Cochrane Library 데이터베이스를 통해 제공되는 논문들을 수집하였다. 총 331 개의 연구가 검색되었으며 최종 13개의 논문을 선정하였다결과: 선정된 13편의 연구에서는 급성기, 아급성기, 만성기의 뇌졸중 환자를 대상으로 하였다. 평가에사용한 가속도계의 종류로는 단축, 이축, 삼축 가속도계, 활동모니터가 있었으며, 20Hz 미만 혹은 이상의 진동수를 설정하고 1개에서 3개 이상을 사용하였다. 또한 가속도계는 일상생활의 상지 및 하지활동 및 움직임을 측정하기 위해서 사용되었으며, 일상생활의 상지 과제를 통해 움직임을 분석할 때는주로 손목, 팔에, 하지의 움직임은 허리, 넓적다리, 복사뼈에 부착하여 분석하였다. 측정활동은 주로상지과제 활동, 걷기 활동 이였으며, 측정활동에 따라 부착부위도 다양하였다. 측정변수로는 총 활동수, 대상자 움직임의 속도, 양측 움직임 비율, 동작분석이 있었으며, 결과로는 모든 연구에서 중재 전, 후 가속도계로 측정한 변수와 기존의 다른 평가도구와의 유의한 상관관계를 보고하였다. 결론: 본 연구를 통해 작업치료사가 뇌졸중 환자의 일상생활활동을 객관적으로 평가할 때 가속도계가 유용하게 활용될 수 있다는 것을 증명하였다. 더 나아가 국내 작업치료 연구를 통해 가속도계가 임상 및지역사회에서 다양한 방법으로 활용될 수 있기를 기대해 본다.

Objective: The purpose of this study was to systematically review the articles using accelerometer to measure activity of daily living of patients with stroke. Methods: Depending on selection criteria, 13 studies were searched for PubMed, EMBASE, and Cochrane library database from February 2014 to March 2014. A total of 331 papers were searched, and 13 of these were selected. Results: In studies of 13 selected, acute, subacute, and chronic patients with stroke were enrolled. The kind of accelerometer was uniaxial, biaxial, and triaxial, activity monitor. Measurement activities were mainly arm activity, walking activity, and attachment sites were also various depending on the measurement activities. A measured variable was the total number of activities, the movement speed of the patients, ratio between affected and nonaffected, and motion analysis. The result indicated that significant correlation with the other assessment tools in all studies. Conclusions: Accelerometer will be applied with a tool for measuring activity of daily living of patients with stroke, depending on activities characteristics. Further, we need accelerometer studies to apply with a variety of assessment in clinical practice or community settings

Accelerometers play a key role in the structural assessment. However, the current electric type accelerometers have certain limitations to apply some structures such as heavy cabling labor, installed sea structure and sensitivity to electromagnetic fields. An optical Fiber Bragg Grating (FBG) accelerometer has many advantages over conventional electrical sensors since their immunity to electromagnetic interference and their capability to transmit signals over long distance without any additional amplifiers, and there is no corrosion from sea water. In this paper, we have developed a new FBG-based accelerometer. The accelerometer consists of two cantilevered type beams and a mass and two rollers. A bragg grating element is not directly glued to a cantilever to avoid possible non-uniform strain in the element. Instead, the bragg grating element will be attached to rotation part that rolled inducing vertical movement of the mass and support cantilever beams so that the bragg grating element is uniformly tensioned to achieve a constant strain distribution. After manufacturing, we will prove the performance and the natural frequency of the accelerometer through the experiment with a vibration shaker. The FBG-based accelerometer is developed for measuring the vibration not exceeding 50 Hz for the marine and civil structures.

Recently, technologies to help the elderly or disabled people who have difficulty in walking are being developed. In order to develop these technologies, it is necessary to construct a system that gathers the gait data of people and analysis of these data is also important. In this research, we constructed the development of sensor system which consists of pressure sensor, three-axis accelerometer and two-axis gyro sensor. We used k-means clustering algorithm to classify the data for characterization, and then calculated the symmetry index with histogram which was produced from each cluster. We collected gait data from sensors attached on two subjects. The experiment was conducted for two kinds of gait status. One is walking with normal gait; the other is walking with abnormal gait (abnormal gait means that the subject walks by dragging the right leg intentionally). With the result from the analysis of acceleration component, we were able to confirm that the analysis technique of this data could be used to determine gait symmetry. In addition, by adding gyro components in the analysis, we could find that the symmetry index was appropriate to express symmetry better.