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The effects of task difficulty and information modality on learning a specific class of procedural tasks, aiming at the prevention of repetitive strain injury (RSI) are presented. The results indicate that learning from a film clip leads to highest learning performance for both easy and difficult exercises and text instruction show fairly good learning.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.apergo.2005.09.005 Byline: Gerard P. van Galen, Hanneke Liesker, Ab de Haan Keywords: Keyboard design; Repetitive strain injury; Muscle tension Abstract: To circumvent the awkward pronated hand position inherent to conventional horizontal keyboards, a vertical, split keyboard was designed with flexible cushions supporting the wrists, allowing relaxed hand and arm postures. During eight twice-weekly 30-min training sessions, the performance and subjective comfort of nine experienced typists were tested. Typing speed and error percentage, and surface electromyographic activity of six forearm muscles and two postural muscles were recorded in separate sessions at the end of each week. Typing speed rapidly recovered to the preset rate of 300 keystrokes/min and error percentages were similar for the two keyboards. The vertical keyboard caused lower muscular activity in especially finger extensor muscles, did not increase postural muscle activity, and self-reported comfort was higher. Thus, the vertical keyboard was easily mastered, was experienced as comfortable, and caused less stress on muscles sensitive to repetitive strain injuries. Author Affiliation: Radboud University Nijmegen, P.O. Box 9104, NL 6500 HE Nijmegen, The Netherlands Article History: Received 4 November 2004; Accepted 27 September 2005

INTRODUCTION When designing workplaces or control panels, one should place controls within the reach of the operator's arm or foot to ensure ease of reach and to optimize human performance [...], The main objectives of this study were to quantify the range of reaching for the upper body with eight degrees of freedom (the trunk and shoulder, elbow, and wrist joints) and the lower body with six degrees of freedom (the hip, knee, and ankle joints). A sweeping algorithm that included trunk and foot motions was used to generate the analytical total reach volume of the human body for young men. Three types of reach volume -- unconstrained arm reach, shoulder-restricted arm reach, and foot reach -- were generated depending on the joint involved in reach activities. The robot kinematics methodology was employed to represent the human body as a multilink system, which was needed for calculating three-dimensional coordinates of the involved joints. The statistical test results showed that the total reach volume analytically generated in this study was nearly identical to that obtained from the direct human body measurements. Applications of this research include generating the human body's reach volume for the purpose of designing work spaces and products.

We investigated, on behalf of a large electronics manufacturer, two types of worker training interventions for their efficacy in preventing unnecessary muscle tension and the symptoms of work-related musculoskeletal disorders. The first intervention, Muscle Learning Therapy[TM] (MLT), used electromyographic (sEMG) feedback and operant conditioning to decrease muscle tension during complex work tasks. The second intervention used adult learning and cognitive behavioral techniques in small group discussion to advance the worker's capabilities for symptom and stress management and problem-solving. Workers were randomly assigned to a control group or one of the two treatment conditions. Prior to training, baseline data were collected using symptom diaries and sEMG recordings of the trapezius and forearm muscles of the left and right arms. The training interventions were conducted for 6 weeks with reinforcement training provided at 18 and 32 weeks post-baseline. Follow-up data were collected after the initial 6-week training period and at 32 weeks, prior to the reinforcement training. Symptom outcomes demonstrated significant differences at 6 weeks, increasing in severity for the control group and declining modestly for the educational group, with little change for the MLT group. These differences were not maintained at further follow-up. The MLT group was consistently effective in reducing muscle tension in the trapezius areas after 6 and 32 weeks, and was partially effective for the forearms. Further testing is recommended of these training interventions, especially with the inclusion of strategic, periodic reinforcement of the worker's learning. Keywords: Musculoskeletal disorders; Worker training; Electromyography

Research is presented quantifying maximum acceptable force levels of six hand motions. These were a handgrip task, power grip with ulnar deviation, pinch grip with wrist extension, pinch grip with wrist flexion, power grip with wrist extension, and power grip with wrist flexion. Depending on motion and frequency, acceptable torque fell between 11% and 19% of maximum isometric levels of torque.

Various methods to determine the most reliable measurement methods in preventing overuse injuries were compared. Self-reporting is the least precise method, while electrogoniometric methods were the best when evaluating wrist flexion and repetition risk factors.

This article discusses a study conducted to determine if visual aids, such as mirrors, could reduce awkward postures, which often led to musculoskeletal discomfort, of assembly line workers. The authors concluded that mirrors and other visual aids provided relief from neck and shoulder discomfort.

Handling roller-press dies has caused numerous work-related musculoskeletal disorders in the leather industry. The dies are quite large (0.61 x 0.30 m), heavy (3.5 kg) and are difficult to handle because of the large pinch span requirements (up to 16 cm). The purpose of this study was to determine the optimum pinch span and optimum crossbar angulation to minimize die handling forces. Five-finger pulp-pinch forces were measured on five males and five females with a force-sensitive-resistor instrumented glove while handling a simulated adjustable die. Maximum pinch forces occurred at pinch spans between 1.27 and 3.81 cm, with average female strengths being 57% of average male pinch strengths. Minimum pinch forces to hold the die occurred at a 45 degrees angulation and increased linearly as the angle approached 90 degrees or the normal vertical orientation. The simplest solution to redesigning the dies is to: (1) decrease the distance between the braces to less than 4 cm and (2) slant the braces at 45 degrees. Keywords: Pinch forces; Pinch span; Musculoskeletal disorders; Roller-press dies

Employers considering redesigning their workplace in order to reduce workers' exposure to work-related musculoskeletal disorders of the upper limbs (WMSDs) should seek to ensure that workers are able to avoid movements or positions that force the joints to exceed 50% of their maximum range. Work benches must be at a suitable height when standing or sitting, and chair height must be suitable for seated positions. Care must also be taken to eliminate any useless actions carried out by machinery operators.

A programme for the reintegration into the workplace of workers with work-related musculoskeletal disorders (WMSDs) of the upper limbs will need to take into account whether tasks should be re-designed to accommodate WMSD-affected workers. The main aim of such a programme should be to eliminate the clinical indications and symptoms connected with the WMSD while also maintaining the worker's productivity. Attention must be given to boosting worker awareness of WMSDs.

Neck tension syndrome in computer-utilizing personnel can be reduced through improved sitting postures. Neck and trapezius muscle exertions are minimized by using a viewing angle of three degrees above the horizontal between the middle of the monitor and eye level. Furthermore, viewing angles of up to 15 degrees above the horizontal are preferred over angles below the azimuth. These values are derived from biomechanical studies of the neck and head.

Female soccer is played in 50 countries and in Sweden it is the most popular female team sport. In four divisions encompassing 800 clubs, there are more than 36,000 female player between the ages of 15 and 35 years old. Studies have been done on injuries sustained by male soccer players and by young female players, but there has been nothing written about the injuries that occur in female, professional, soccer players. For a period of one year, all injuries occurring in two professional female soccer teams were recorded. There were 41 players in the sample, and 33 of them (80 percent) sustained a total of 78 injuries during the year. During games, there were 24 injuries per 1,000 hours of play. In training, there were 7 injuries per 1,000 hours of play. Injuries to the lower extremities accounted for 88 percent of the injuries recorded; 49 percent affected the knees or ankles. Only 15 percent of all injuries were classified as major, compared with 36 percent that were moderate and 49 percent that were minor. Major injuries included trauma (usually the result of contact with an opponent) and torn ligaments or cartilage. During training, and at the beginning and end of the season, overuse injuries were common. Professional female soccer players have a high rate of injury but relatively few injuries are major. It is suggested that the majority of overuse injuries, which constituted 28 percent of all injuries, could be prevented by changes in training. (Consumer Summary produced by Reliance Medical Information, Inc.)

Previously sedentary individuals who begin exercise programs frequently become injured, usually due to overuse injuries of the leg. These range from patellofemoral (kneecap-thighbone) pain to stress fractures. Transmission of shock from the ground through the leg and spine contributes to these overuse injuries. In response to this fact, footwear, especially running shoes, have been redesigned. However, military recruits are at the same risk for overuse injuries, but little attention has been paid to alterations in military footwear. The effectiveness of commercially available neoprene insoles on the incidence of overuse injuries during the training of 237 new recruits was compared with the prevalence of injuries among 1,151 control recruits, who used no insole. Injuries occurred in 23 percent of the experimental group and 32 percent of the control group. Overuse injuries constituted 91 percent of the experimental group injuries and 86 percent in the control group, with the remainder being acute traumatic injuries. The average incidence of total injuries and of tibial stress syndrome was significantly lower in the insole group. There were 14 stress fractures in the control group but none in the insole group. The study suggests that neoprene insoles can decrease the incidence of overuse injuries, including tibial stress syndrome and stress fractures, in military recruits. (Consumer Summary produced by Reliance Medical Information, Inc.)