Effects of box handle position and carrying range on bi-manual carrying capacity for females.

This study utilizes a psychophysical approach to examine the effects on carrying capacity for bi-manual carrying tasks involving different handle positions and carrying ranges. A total of 16 female subjects participated in the experiment in groups of two people, and each group of subjects performed the tasks in a random order with 12 different combinations of carrying task. The independent variables are handle position (upper, middle, lower) and carrying range (F-F: floor height carried to floor height, F-W: floor height carried to waist height, W-W: waist height carried to waist height, W-F: waist height carried to floor height), the dependent variable is the maximum acceptable carried weight (MAWC), heart rate (HR), and the rating of perceived exertion (RPE). The results show that the handle position has a significant effect on MAWC and overall RPE but no significant effect on HR. Carrying range has a significant effect on the MAWC and HR, but no significant effect on overall HR. The handle position and carrying range have a significant interaction on the MAWC and HR. The RPE for different body parts shows significant differences, and the hands feel the most tired. Overall, this study confirms that the lower handle position with the W-W carrying range is the best combination for a two-person carrying task.

The effect of wok size and handle angle on the maximum acceptable weights of wok flipping by male cooks.

A wok with a straight handle is one of the most common cooking utensils in the Asian kitchen. This common cooking instrument has seldom been examined by ergonomists. This research used a two-factor randomized complete block design to investigate the effects of wok size (with three diameters - 36 cm, 39 cm and 42 cm) and handle angle (25°, 10°, -5°, -20°, and -35°) on the task of flipping. The measurement criteria included the maximum acceptable weight of wok flipping (MAWF), the subjective rating and the subjective ranking. Twelve experienced males volunteered to take part in this study. The results showed that both the wok size and handle angle had a significant effect on the MAWF, the subjective rating and the subjective ranking. Additionally, there is a size-weight illusion associated with flipping tasks. In general, a small wok (36 cm diameter) with an ergonomically bent handle (-20° ± 15°) is the optimal design, for male cooks, for the purposes of flipping.

Effects of carrying methods and box handles on two-person team carrying capacity for females.

This study used a psychophysical approach to examine the effects of carrying methods and the presence or absence of box handles on the maximum acceptable weight carried and resulting responses (heart rate and rating of perceived exertion) in a two-person carrying task. After training, 16 female subjects performed a two-person carrying task at knuckle height for an 8-h work period. Each subject performed 4 different carrying combinations two times. The independent variables were carrying methods (parallel and tandem walking) and box handles (with and without handles). For comparison with two-person carrying, the subjects also performed one-person carrying. The results showed that the maximum acceptable weight carried (MAWC), heart rate (HR), and rating of perceived exertion (RPE) were significantly affected by the presence of box handles. However, the subjects' MAWC, HR, and RPE values were not significantly influenced by the carrying methods. The test-retest reliability of the psychophysical approach was 0.945. The carrying efficiency of two-person carrying was 96.2% of the one-person carrying method. In general, the use of box with handles allows the subjects to carry a higher MAWC (with lower HR and RPE) compared to carrying boxes without handles.

VDT screen height and inclination effects on visual and musculoskeletal discomfort for Chinese wheelchair users with spinal cord injuries.

This study investigated the visual fatigue and musculoskeletal discomfort for wheelchair users in a VDT data entry task. Eight Chinese male wheelchair users were recruited as participants to perform 9 different experimental combinations. Three screen heights and three screen inclinations were evaluated. Visual fatigue was measured using the change in critical fusion frequency (CFF), near point accommodation (NPA) and a visual complaint questionnaire. Musculoskeletal discomfort was estimated using the rating of perceived exertion (RPE). Each participant performed a data-entry task within a 30 min period using random orders. All participants during the data-entry operation used the upright posture with the participant's lower and upper arms forming right angles. The results showed that the screen height and screen inclination significantly affected visual fatigue and musculoskeletal discomfort. On average, the optimal screen height choice for wheelchair users was at eye-level height or 5 cm below eye level with a vertical screen inclination.

Mode of grasp, materials, and grooved chopstick tip on gripping performance and evaluation.

This study evaluated the effects of the mode of grasping, chopstick materials, and the groove of the chopstick-tip on gripping performance of 32 participants, among whom 16 were accustomed to using chopsticks with a pliers-grasping mode and the other 16 with a scissors-grasping mode. Based on a random sequence, 8 kinds of chopsticks with different combinations (materials: bamboo, wood, plastic, and stainless steel, with and without grooves in the chopstick-tip) were used to carry out the action of gripping two different objects (peanuts and longan). The time to finish gripping 50 pieces of peanut and longan, the number which fell on the table when gripping, the subjective effort and the subjective preference were measures of efficiency of pinching for 8 kinds of chopsticks. Analysis showed that chopstick materials significantly affect time of gripping. The large object (such as longan) could be gripped more easily with the pliers-grasping mode or gripped with the grooved chopstick-tip. However, for small objects (such as peanuts), there was no significant difference in performance whether the chopstick-tip was grooved or not. A combination of bamboo chopsticks with grooved tips used with a pliers-grasping seem preferrable for more favorable gripping performance.

Effect of VDT keyboard height and inclination on musculoskeletal discomfort for wheelchair users.

This study investigated the effect of keyboard height and inclination on musculoskeletal discomfort for wheelchair users. Eight Taiwanese male wheelchair users (28.75 +/- 8.75 years) were recruited as participants to perform nine experimental combinations of data entry tasks. Three keyboard heights and three inclinations were evaluated. Musculoskeletal discomfort was estimated by Rating of Perceived Exertion and Subjective Preference Ranking. Each subject performed a data entry task for all nine experimental combinations in a random order. The seated posture of all participants during the data entry operation was the upright posture. The height of the screen's center was adjusted according to the eye level of each subject. Analysis showed the keyboard height and keyboard inclination significantly affected rating of musculoskeletal discomfort. It is suggested that the optimum keyboard height choice is elbow-level height or 5 cm below elbow level with the keyboard inclination horizontal to the seat of the wheelchair.

Maximum acceptable weights for asymmetric lifting of Chinese females.

This study used the psychophysical approach to evaluate the effects of asymmetric lifting on the maximum acceptable weight of lift (MAWL) and the resulting heart rate, oxygen uptake and rating of perceived exertion (RPE). A randomized complete block factorial design was employed. Twelve female college students lifted weights at three different lifting frequencies (one-time maximum, 1 and 4 lifts/min) in the sagittal plane and at three different asymmetric angles (30 degrees, 60 degrees, and 90 degrees ) from the floor to a 68-cm height pallet. This lifting experiment was conducted for a 1-h work period using a free-style lifting technique. The MAWLs for asymmetric lifting were significantly lower than those for symmetric lifting in the sagittal plane. The MAWL decreased with the increase in the angle of asymmetry. However, the heart rate, oxygen uptake and RPE remained unchanged. Though the MAWL decreased significantly with lifting frequency, both the physiological costs (heart rate and oxygen uptake) and rating of perceived exertion increased with the increase in lift frequency. The most stressed body part was the arm. Lifting frequency had no significant effect on the percentage decrease in MAWL from the sagittal plane values. On average, decreases of 5%, 9% and 14% for MAWL at 30 degrees, 60 degrees and 90 degrees asymmetric lifting, respectively, were revealed. This result was in agreement with the findings of Chinese males studied by Wu [Int. J. Ind. Ergonom. 25 (2000) 675]. The percentage decrease in MAWL with twisting angle for the Chinese participants was somewhat lower than those for Occidental participants. In addition, even though there was an increase in heart rate and RPE with the increase in the symmetrical lift angle for Occidental participants, it was different from the Chinese participants. Lastly, the 1991 NIOSH equation asymmetry multiplier is more conservative in comparison with the results of the present study.

Ergonomics study on the handle length and lift angle for the culinary spatula.

The culinary spatula (turning shovel) is one of the most common cooking tools used in the kitchen in Asia. However, the culinary spatula has seldom been ergonomically investigated. When a person uses a spatula to cook food, the operations involve repetitive bent-wrist motions, such as dorsiflexion, palmary flexion, and radial and ulnar deviations. These movements may cause cumulative trauma disorders in the upper extremities, and in particular carpal tunnel syndrome. A poorly designed culinary spatula will be ergonomically inefficient and cause injury to the hand and wrist. The purpose of this study was to investigate the effects of spatula handle length and lift angle on food-frying, food-turning, and food-shoveling performance. Eight female subjects were tested using 16 different culinary spatulas, with four different handle lengths (20, 25, 30 and 35 cm) and four different lift angles (15 degrees, 25 degrees, 35 degrees and 45 ). The criterion measures included cooking performance, and rating of perceived exertion. The subjects ranked their preference after all of the tasks in the tests were completed. The results showed that: (1) The handle length had a significant influence on the cooking performance, and rating of perceived exertion. The optimal handle lengths for frying food, turning food, and shoveling food were 20, 25 and 25 cm, respectively. (2) The lift angle significantly affected the cooking performance, and rating of perceived exertion. The optimal lift angles for frying food, turning food, and shoveling food were 15 degrees, 15 degrees and 25 degrees, respectively. (3) Both the handle length and lift angle had significant effects on subjective preference. For the handle length, the 20 cm length was the best. For the lift angle, the 25 angle was the best. (4) In general, a spatula with a 20 cm handle length and 25 degrees lift angle was the best. A spatula with a 25 cm handle length and 15 lift angle was the second most preferred. (5) However, to prevent subjects from touching the edge of a hot pan, a spatula with a 25 cm handle length and 25 lift angle is suggested.