Load Acceleration and Footstep Strategies in Asymmetrical Lifting and Lowering Alain Delisle, Micheline Gagnon, Pierre Desjardins, 185-195 Comparison of Two Methods for Judging Distances Near Overhead Power Lines Daniel Imbeau, Joseph-Jean Paques, Sylvie Bergeron, Réal Bourbonničre, 196-211 Optimum Design for Emergency Stop Button on Robot Teach Pendants Kyu Sik Kwon, 212-217 Dental Workers, Musculoskeletal Cumulative Trauma, and Carpal Tunnel Syndrome, Who is at Risk? A Pilot Study Valerie J. Rice, Bradley Nindl, John S. Pentikis, 218-233 A Method for Response Time Measurement of Electrosensitive Protective Devices Marek Dźwiarek, 234-242 Safety Management in Coal Mines-Risk Assessment Zygmunt T. Niczyporuk, 243-250 A Multilevel Approach to Manual Lifting in Manufacturing Industries Berman Kayis, Kamal Kothiyal, 251-261

Notes:

Assessment of Health Risks in Canteen Kitchen Anneli Pekkarinen, Hannu Anttonen, Juhani Niskanen, 262-267

Load Acceleration and Footstep Strategies in Asymmetrical Lifting and Lowering
Alain Delisle, Micheline Gagnon, Pierre Desjardins, 185-195

Accelerated execution effects for lifting and lowering a 12-kg box using two footstep strategies associated with experienced workers were studied. Eight healthy male participants performed a normal and an accelerated execution of a lifting task and a lowering task, using a minimal feet displacement strategy (oblique-step) and a strategy with a step (crossed-step). It was hypothesized that the accelerated executions, as compared to the normal executions, would have a different effect on L5/S1 resultant moment, body posture, and on other kinematic variables. A tridimensional dynamic rigid body model was used to compute L5/S1 resultant moments. Results showed that the accelerated condition did not reduce body asymmetry of posture, but it reduced the length of the path of the global centre of gravity and the duration of the supporting phase of the box, and it did not significantly affect L5/S1 maximal resultant moments for lifting but increased them for lowering. These results indicate that the net work production for accelerated strategies might be smaller, which may represent an economy of energy. Furthermore, the results showed that the use of an accelerated strategy for lowering should be avoided.

Comparison of Two Methods for Judging Distances Near Overhead Power Lines
Daniel Imbeau, Joseph-Jean Paques, Sylvie Bergeron, Réal Bourbonničre, 196-211

Sixteen certified crane operators performed several series of boom movements towards a segment of a typical power line using a 100-ton lifting capacity crane equipped with an 18-m boom, a single lifting cable, and a hard ball hook. The operators were instructed to stop the crane movement when the lifting cable reached the edge of the danger zone located at 3 m from the power line. To achieve each maneuver, they evaluated the distance between the nearest wire and their crane using two methods: free sighting and the use of highly visible markers delineating the edge of the danger zone. The dependent measure was the distance between the lifting cable and the edge of the danger zone. Results showed that operators were generally unreliable when judging the distance between their crane and the power line when sighting the power line directly, but the use of markers proved to be much more precise and reliable in targeting the edge of the danger zone.

Optimum Design for Emergency Stop Button on Robot Teach Pendants
Kyu Sik Kwon, 212-217

This study deals with designing robot teach pendants for industrial robots. The emergency stop button on robot teach pendants is the primary safety device for industrial robots. Recommendations for the design of the emergency stop button were proposed based on experimental evaluations. Human performance was measured by the reaction time necessary to press the button on a pendant. The variation factors were randomly combined by seven button locations and three different button sizes. The results indicated that the shortest reaction time was obtained for the 38-mm button located on the left and left-down of the seven button positions on the pendant.

Dental Workers, Musculoskeletal Cumulative Trauma, and Carpal Tunnel Syndrome: Who is at Risk? A Pilot Study
Valerie J. Rice, Bradley Nindl, John S. Pentikis, 218-233

A pilot study was conducted at a dental clinic to identify (a) the prevalence of musculoskeletal cumulative trauma disorders (MCTD), (b) associated symptoms (with special attention paid to carpal tunnel syndrome [CTS]), and (c) practitioners at risk. Videotapes, 2 questionnaires, a medical record review, and interviews were used. Forty-five dental workers participated and were classified into 3 categories: (a) dentists, (b) dental assistants and special assistants (DA/SA), and (c) dental hygienists and dental assistant-expanded function (DH/DAEF). Categorical data were analyzed using the chi-square statistic and risk ratios. The Fisher exact probability test was used for categorical data with a small cell. One or more symptoms associated with CTS were noted by 75.6 % of the dental workers, 11% reported diagnosed CTS, and 53% reported back and shoulder pain. Both psychosocial factors and job demands appear to be associated with MCTD. All 3 categories of dental workers reported MCTD symptoms, and the DH/DAEF group was found to be at greatest risk for developing upper extremity symptoms, CTS, and back pain.

A Method for Response Time Measurement of Electrosensitive Protective Devices
Marek Dźwiarek, 234-242

A great step towards the improvement of safety at work was made when electro-sensitive protective devices (ESPDs) were applied to the protection of press and robot-assisted manufacturing system operators. The way the device is mounted is crucial. The parameters of ESPD mounting that ensure safe distance with respect to the controlled dangerous zone are response time, sensitivity, and the dimensions of the detection zone. The proposed experimental procedure of response time measurement is realised in two steps, with a test piece penetrating the detection zone twice. In the first step, low speed penetration (at a speed vm) enables the detection zone border to be localised. In the second step of measurement, the probe is injected at a high speed vd. The actuator rod position is measured and when it is equal to the value L registered by the earlier measurements, counting time begins as well as the monitoring of the state of the equipment under test (EUT) output relays. After the state changes, time tp is registered. The experimental procedure is realised on a special experimental stand. Because the stand has been constructed for certification purposes, the design satisfies the requirements imposed by Polski Komitet Normalizacyjny (PKN, 1995). The experimental results prove the measurement error to be smaller than ± 0.6 ms.

Safety Management in Coal Mines-Risk Assessment
Zygmunt T. Niczyporuk, 243-250

The present state of accident hazard at work in the Polish mining industry is presented. A comparison is made of the accident indices in relation to other countries. A reference is made to the work safety management system implemented in the mines. Safety management is discussed in terms of risk management. On the basis of the natural death index and that of accidents at work, numerical scales are presented defining the limits of the inadmissable, tolerable, and acceptable risk. The course of variation of risk indices for fatal, serious, and minor accidents is evaluated. The results of the assessment for all kinds of accidents at work in the mining industry are presented.

A Multilevel Approach to Manual Lifting in Manufacturing Industries
Berman Kayis, Kamal Kothiyal

Musculoskeletal injuries are often the consequences of wrong postural configurations used during Manual Materials Handling (MMH). This eventually leads to large payout of worker's compensation and loss of production time. A simulated study of back injury risks has been carried out on seven selected manufacturing industries to identify and evaluate harmful working postures. For each MMH task, OWAS (Ovako Working Posture Analysing System) codes have been identified with the help of motion study pictures. Also, Chaffin's biomechanical model was used to calculate L5/S1 load compression values on the spine during MMH activities. The multilevel approach adopted was a combination of OWAS and Chaffin's biomechanical model. The application of a digitiser enabled us to identify the coordinates and it made a subsequent evaluation of the angles of each body link possible.