Comparisons of physical exposure between workers harvesting apples on mobile orchard platforms and ladders, part 1: Back and upper arm postures.

This study compared farmworkers' exposure to non-neutral postures using a new mobile platform apple harvesting method and the traditional method using ladders. Twenty-four workers were recruited and assigned into three groups: ladder workers (n = 8) picking apples from full trees using a ladder, mobile platform workers (n = 8) picking apples from upper part of the trees while standing on a moving platform, and ground-based mobile platform workers (n = 8) picking apples from lower part of the trees which the mobile platform workers left out. Upper arm and back inclinations were continuously monitored during harvesting using tri-axial accelerometers over full work shifts (~8 h). Upper arm posture was characterized as the percentage of time that upper arm flexion and abduction exceeded 30°, 60°, and 90°. Back posture was characterized as the percentage of time that torso angles (sagittal flexion or lateral bending) exceeded 10°, 20°, and 30°. The 10th, 50th, and 90th postural percentiles were also calculated. The platform workers had lower exposures to upper arm flexion and abduction than the ground and ladder workers. There were no differences in torso angles between the ladder and mobile platform workers; however, the ground workers were exposed to more and greater percentages of time in torso flexions.

Comparisons of physical exposure between workers harvesting apples on mobile orchard platforms and ladders, part 2: Repetitive upper arm motions.

Farmworkers are exposed to physical risk factors including repetitive motions. Existing ergonomic assessment methods are primarily laboratory-based and, thus, inappropriate for use in the field. This study presents an approach to characterize the repetitive motions of the upper arms based on direct measurement using accelerometers. Repetition rates were derived from upper arm inclination data and with video recordings in the field. This method was used to investigate whether harvesting with mobile platforms (teams harvesting apples from the platform and the ground) increased the farmworkers' exposure to upper arm repetitive motions compared to traditional harvesting using ladders. The ladder workers had higher repetitive motions (13.7 cycles per minute) compared to the platform and ground workers (11.7 and 12.2 cycles per minutes). The higher repetitions in the ladder workers were likely due to their ability to work independently and the additional arm movements associated with ladder climbing and walking.

#drunktwitter: Examining the relations between alcohol-related Twitter content and alcohol willingness and use among underage young adults.

PURPOSE: Despite the importance of social networking sites on young adult alcohol use, few studies have examined Twitter as a conduit for sharing drinking behavior. However, this work generally uses random samples of tweets and thus cannot determine the extent to which Tweets correspond with self-reported drinking cognitions or behaviors. The primary aims of the present study were to (1) document basic patterns of alcohol-related Twitter activity in a subsample of young adult drinkers, and (2) examine whether willingness to drink, alcohol use, and negative consequences are associated with alcohol-related tweeting behavior. METHODS: 186 young adults age 18-20 completed an online survey and provided Twitter handle information. From these participants, a random sample of 5000 Tweets was coded by a trained team to determine whether tweets were related to alcohol use or not. Ordinary least squares regression analyses were conducted to determine whether the proportion of alcohol-related Tweets is associated with self-reported alcohol use willingness, behaviors, and negative consequences. RESULTS: Results indicated that not only are alcohol-related tweets common among young adults, but that the proportion of one's overall tweets that are related to alcohol is significantly associated with willingness to drink, alcohol use, and negative consequences. CONCLUSIONS: The results of this study are an important step to understanding how digital behavior (e.g., posting about alcohol on Twitter) is related to an individual's self-reported drinking cognitions, alcohol use, and negative consequences and has implications for the way Twitter data can be used for public health surveillance and interventions.

Attrition and performance of community college transfers.

Community colleges are an important part of the US higher education landscape, yet the aptitude and preparedness of student transfers to baccalaureate institutions is often called into question. Examining transcript records and demographic information of nearly 70,000 students across over 15 years of registrar records at a public university, this study performed a descriptive analysis of the persistence, performance, and academic migration patterns of community college transfers, transfers from four-year institutions, and freshmen entrants. We found little difference between community college transfers and freshmen entrants in terms of post-transfer grades and persistence. Transfers from four-year institutions had higher grades but also had higher attrition rates than their peers. This study also found no strong evidence of transfer shock on students' post-transfer grades. When examining the tendencies of students to shift fields of study during their educational pursuits, the academic migration patterns of transfer students were more concentrated than those of freshmen entrants.

Whole Body Vibration Exposures and Health Status among Professional Truck Drivers: A Cross-sectional Analysis.

Many professional truck drivers suffer from low back pain (LBP) which is thought to be associated with exposure to whole-body vibration (WBV). The objectives of this study were to: (i) characterize general health, regional body pain and WBV exposures, (ii) evaluate the associations between different WBV parameters and health outcomes, and (iii) determine whether there were factors which affect a truck driver's WBV exposures. This study analyzed WBV exposures from 96 long-haul truck drivers over their regular work shift (6-15h) per International Standards Organization (ISO) 2631-1 and 2631-5 WBV standards. This study also evaluated regional body pain (10-point scale), low back disability (the Oswestry Disability Index), and physical and mental health (the Short Form 12-item Health Survey). The results demonstrated that the daily vector sum WBV exposures [A(8), VDV(8) and Sed(8)] were above action limits while the predominant z-axis exposures were below action limits. Among all the musculoskeletal outcomes, LBP was the most prevalent (72.5%) with average LBP score of 2.9 (SD: 2.0). The SF-12 health scores demonstrated that truck drivers in general had lower physical health status than the general US population (P's < 0.04) and that physical health status decreased as WBV exposures increased (P = 0.03). In addition, the correlations between the WBV measures and health outcomes indicated that A(8) exposure measures had a stronger link to musculoskeletal (LBP) and other health outcomes than the VDV(8) and Sed(8) measures. Finally, seat manufacturer and seat age were two factors which had a strong influence on WBV exposures.

The effects of work surface hardness on mechanical stress, muscle activity, and wrist postures.

BACKGROUND: Contact pressure is a risk factor which can contribute to musculoskeletal disorders. OBJECTIVE: The objective of the present study was to determine whether a work surface with a soft, pliable front edge could reduce contact pressure, muscle activity, and subjective musculoskeletal comfort, and improve wrist posture relative to a conventional, hard work surface. METHODS: In a repeated-measures blinded experiment with eighteen subjects (8 females and 10 males), contact pressure, wrist posture, typing productivity, perceived fatigue, wrist and shoulder muscle activity, and subjective comfort were compared between the two different work surfaces during keyboard use, mouse use and mixed mouse and keyboard use. RESULTS: The results showed that across the three modes of computer work, the contact pressure was lower on the soft-edge work surface compared to the conventional work surface (p's <0.03) and subjects reported to have less perceived fatigue in the forearms and wrists. No differences in muscle activity, wrist posture, and subjective comfort were measured between the two work surfaces. CONCLUSIONS: Given the significant reduction in contact pressure and corresponding lower ratings in perceived fatigue, the soft-edge work surface subjectively and objectively improved measures of contact stress which may reduce physical exposures associated with the onset and development of musculoskeletal disorders.

The effect of key size of touch screen virtual keyboards on productivity, usability, and typing biomechanics.

OBJECTIVE: We investigated whether different virtual keyboard key sizes affected typing force exposures, muscle activity, wrist posture, comfort, and typing productivity. BACKGROUND: Virtual keyboard use is increasing and the physical exposures associated with virtual keyboard key sizes are not well documented. METHOD: Typing forces, forearm/shoulder muscle activity, wrist posture, subjective comfort, and typing productivity were measured from 21 subjects while they were typing on four different virtual keyboards with square key sizes, which were 13, 16, 19, and 22 mm on each side with 2-mm between-key spacing. RESULTS: The results showed that virtual keyboard key size had little effect on typing force, forearm muscle activity, and ulnar/radial deviation. However, the virtual keyboard with the 13-mm keys had a 15% slower typing speed (p < .0001), slightly higher static (10th percentile) shoulder muscle activity (2% maximum voluntary contractions, p = .0 I), slightly greater wrist extension in both hands (2 degrees to 3 degrees, p <.01), and the lowest subjective comfort and preference ratings (p < .1). CONCLUSIONS: The study findings indicate that virtual keyboards with a key size less than 16 mm may be too small for touch typing given the slower typing speed, higher static shoulder muscle activity, greater wrist extension, and lowest subjective preferences. APPLICATIONS: We evaluated the effects of virtual keyboard key sizes on typing force exposures, muscle activity, comfort, and typing productivity.

Differences in typing forces, muscle activity, comfort, and typing performance among virtual, notebook, and desktop keyboards.

The present study investigated whether there were physical exposure and typing productivity differences between a virtual keyboard with no tactile feedback and two conventional keyboards where key travel and tactile feedback are provided by mechanical switches under the keys. The key size and layout were same across all the keyboards. Typing forces; finger and shoulder muscle activity; self-reported comfort; and typing productivity were measured from 19 subjects while typing on a virtual (0 mm key travel), notebook (1.8 mm key travel), and desktop keyboard (4 mm key travel). When typing on the virtual keyboard, subjects typed with less force (p's < 0.0001) and had lower finger flexor/extensor muscle activity (p's < 0.05). However, the lower typing forces and finger muscle activity came at the expense of a 60% reduction in typing productivity (p < 0.0001), decreased self-reported comfort (p's < 0.0001), and a trend indicating an increase in shoulder muscle activity (p's < 0.10). Therefore, for long typing sessions or when typing productivity is at a premium, conventional keyboards with tactile feedback may be more suitable interface.