Surface electromyograms(EMG) during test contractions(TCs) were studied to assess the muscle strain in simulated mushroom picking. Additionally, the duration of the TC for the effective assessment was investigated. Nine female subjects performed standardized shoulder abduction and a stooped posture for one minute as TCs. Each experiment consisted of a 60-min rest, three work periods (W1-W3), a 30-min rest, and two work periods (W4 and W5) separated by a 30-min rest period. The duration of each work period was about 20min. A total of 18 TCs was performed between the work periods and every 10 minutes in the rest periods. EMGs were recorded from the trapezius, infraspinatus, deltoid, and erector spinae muscles. The amplitude of EMG(AEMG) and mean power frequency(MPF) of EMG were calculated. Each TC was divided equally into three parts. Ratings of perceived exertion (RPE) in the neck, shoulder and low-back were reported during TCs. The work increased RPE of all the parts. AEMG and RPE were increased and MPF was decreased by W1, W2 and W3 in the neck and shoulder muscles. MPF of the erector spinae was increased by the work. The results were not affected by the duration of TCs and the parts during the TCs. AEMG and MPF fluctuated before W1 although the changes of RPE were small. Averaging several TCs was recommended to get stable results from TCs. EMG changes and appropriate TC conditions were discussed in relation to the adaptation in fatiguing contractions.

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This study was aimed to compare the variations in cerebral oxygenation, blood pressure and center-of-foot pressure after standing from sitting and supine positions at normal (22°C) and high (32°C) room temperatures. Thirty young adults stood up from a resting posture (sitting or supine position) and kept the static standing posture for 90 sec. Meanwhile, their center-of-foot pressure (COP), blood pressure, and cerebral oxygenation kinetics were measured in continuity. The change of the frequency domain low-to-high frequency (LF/HF) ratio of the R-R interval before and after standing from a supine position was significantly higher than that from a sitting position under both temperature conditions. Blood pressure as well as total and oxygenated hemoglobin levels decreased immediately after standing up and the ratio of blood pressure change when moving from a supine position to standing at high room temperature was the largest as compared with the other conditions. Total hemoglobin (Hb) volume was found to temporarily decrease after standing and required 22-24 sec to recover when the subject started from the sitting position and 33-36 sec when the subject started from the supine position. Cerebral oxygenation kinetics tended to be larger under high, rather than normal, temperature conditions. All COP parameters after standing were significantly larger in the high temperature condition than in the normal temperature condition. Body sway after standing was larger in the high temperature condition than in the normal temperature condition and after standing from a supine position than from a sitting position. In conclusion, cerebral oxygenation kinetics and blood pressure measured after the subject moved to the standing position changed dramatically under high temperature conditions, and variations in this parameter may influence body sway.

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Recently, few studies regarding the changes in BMI with age have been reported. In the present study, the wavelet interpolation method (WIM) was applied to the changes in BMI with age from the first grade of elementary school until the second year of high school in Korean girls, and the relationship between age at the maximum peak velocity (MPV) of BMI and age at menarche was confirmed by determining the age at MPV of BMI. Age at menarche and activity status were obtained from questionnaires given to 263 second grade high school girls in the Pusan area of South Korea. Moreover, longitudinal growth data on height and weight from the first grade of elementary school until the second year of high school (from 1997 to 2008) were obtained from health examination records. BMI was calculated from height and weight values from the first grade of elementary school until the second year of high school, and wavelet interpolation was applied to the distances of BMI in each grade. The change curve of BMI with age was determined by wavelet interpolation, and the age at MPV of BMI was determined from the changes in the velocity curve with age as the differentiation curve. Age at MPV of BMI was found to be 12.76±1.6 years, and age at menarche to be 12.34±1.1 years. The interval in age at the two times was -0.42±1.6 years, and a significant difference was seen between age at menarche and age at MPV of BMI. The reason that the age at menarche was a little earlier than the age at MPV of BMI is hypothesized to be abnormal melatonin levels influenced by lack of sleep in Korean school girls. However, it is proposed that the age at MPV of BMI is valid as the critical period for the age at menarche.

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The present study aimed at ergonomic evaluation of the prevalence of work-related musculoskeletal disorders among construction labourers working in unorganized sectors in West Bengal, India. A modified Nordic questionnaire was applied to one hundred forty male and ninety female construction labourers to acquire information about musculoskeletal symptoms like pain in different body parts. Work-rest schedules of the labourers in different work activities were studied. Working postures were analyzed by means of the Rapid Entire Body Assessment (REBA) tool. Body part discomfort (BPD) scale was used to assess the intensity of feeling of discomforts in the different body parts. It was revealed that the labourers performed repetitive, stressful work for a long period of time in a single work-rest cycle and the load lifted and carried by them were more than the NIOSH recommended weight limit. The analyses of working postures revealed that most of their working postures were unsafe and ranked under REBA action level 3 and 4. The results obtained by applying the Nordic questionnaire and BPD scale revealed that the prevalence of pain in various regions of the body, especially low-back pain, was alarmingly high in both male and female labourers. Training for safe lifting of materials, proper work-rest schedule, modifications of some working procedures and the use of ergonomically designed equipment may certainly reduce the work-related musculoskeletal disorders and improve the health status of construction labourers working in unorganized sectors.

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This paper describes the development of a set of multiple linear regression equations for predicting maximal voluntary static handgrip strength of males and females, 5-89 years of age, in each hand. Equations are presented for predicting handgrip strength of the left and right hands from: (i) overall body descriptive variables alone -- age, sex, body weight and stature, (ii) overall descriptive variables plus pinch strength variables, and (iii) pinch strength variables alone. A data set on 182 persons living in the United States was used for this study. Two-thirds of the observations were used to develop the models and the rest for validating them. Models were found with 3-5 variables, R2 ranging from 0.80-0.87, and root mean square error from 4.7-5.8 kg. Among the most common predictor variables that appeared in the models were: stature, age, sex, and the stronger pinches (chuck, lateral and pulp-2). Model validation indicated a greater tendency to over-predict left hand strength but no directional tendency for right hand strength. Also prediction accuracy (mean absolute percentage error) ranged from 14.9-21.0 %, with about equal magnitudes in the two hands. The regression model coefficients were refined by recombining the data set of 182 observations and performing the appropriate regressions analysis.

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The purpose of this study is to extract components of the capacity which elderly people have in comprehending electrical devices and determine its relationship with the components. Initially, we proposed a hypothesis through examining previous studies. The hypothesis states that the capacity which elderly people have mainly consists of four components, i.e., motivation, working memory, logical thinking and experience with personal computers (PC) or mobile phones. Then, some tests were conducted to examine the hypothesis. In this research, elderly people were interviewed about their impressions and experience with electrical devices. Moreover, three tests were conducted including, card sorting, tasks using digital video cameras and a test to measure working memory. As analysis methods, the Quantification 1 was used to see which component was important. In addition, Boolean algebra was conducted to simplify the components and understand some relationships. As a result, a relationship with the components in electrical devices was revealed. Furthermore, the use of Boolean algebra and the Quantification 1 suggested that the experience with PCs or mobile phones was the most important component for elderly people.

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The present study investigated the effect of keypad layout on the ease of operating small cell phones with the thumb in one-handed operations by young and elderly male and female participants. Eighteen young participants (9 males and 9 females) and 12 elderly participants (6 males and 6 females) operated 9 different keypads modeled after commercially available cordless handsets. Keypads designed by using the L9 orthogonal array differed in vertical pitch (V-Pitch: 7, 8, 9 mm) between keys, horizontal pitch (H-Pitch: 10, 11, 12 mm) between keys, the margin below the bottom row of keys (B-Margin: 5, 13, 21 mm), and phone body width (P-Width: 38, 41, 44 mm). Results concerning subjective overall usability showed the lowest scores for a V-Pitch of 7 mm and a B-Margin of 5 mm in most groups. However, for the female participants, with shorter thumbs, the increase in V-pitch did not improve operability. In the elderly participants, miskeying frequently occurred at dial keys of specific numbers. These findings suggest that the preferable keypad layout differs between different age groups and between male and female participants.

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