Work-related low back pain and cervicobrachial disorders have become increasingly common among nursing personnel with the increase in the number of social welfare institutions and workers. The aim of this study is to assess the burden on the low backs of personnel caring for children. We measured work content, working time, posture and muscular activity in 16 nursery workers in three different types of institutions for healthy and handicapped children. The working time and posture of 7 nursery teachers in a public nursery school for healthy children (A school), 7 nursing workers (4 nursery teachers and 3 nursery instructors) in a public daycare center for mentally and physically handicapped children (B center), and 2 nursery instructors in a private home for severely handicapped children (C home) were analyzed. The muscular activity of the erectores spinae muscle of three subjects was measured using a newly developed EMG monitor (portable EMG monitor, PEMM). The following results were obtained. The average length of a lesson or activity in A school was greater than that in B center and C home. The time required by care for meals was longest in C home. The arrangement and rearrangement times were longest in the classes of children aged 3-5 in A school. The time occupied for clerical work and other work was relatively longer, while recess including lunch time was approximately one hour. The most commonly observed posture was sitting on the floor in all kinds of classes, with this occurring most often in C home. Hazardous postures such as bending forward, squatting, and kneeling appeared in 11-18% (48-81 min) of a day's working time. The average muscular activity of the erectores spinae muscle of three subjects throughout a day was approximately 10% of the maximum isometric contraction (% maximum work load, %MWL), when muscular activities were measured by PEMM. The relatively high %MWL values (19-27 %MWL) were obtained at a slightly bending posture and a kneeling posture, while lower (1-9 %MWL) values were observed at a sitting posture. The %MWL values at a sitting posture varied according to such conditions as duration of sitting, back rest, weight on the arms, twisting of the trunk, and hip movement. The risky nature of the sitting posture are also discussed.
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We had children from elementary school and from junior high school practice overhand throwing with tennis ball for four weeks. All children were taught in the same way, regardless of age, and the effects of this practice, as seen from throwing a tennis ball, a baseball, and a softball, were examined in terms of the most appropriate age range of children to whom this practice should be emphasized.1. The distance thrown increased with age in both boys and girls, regardless of the type of ball. The greater increment was seen between seven and nine years of age in boys, and between nine and eleven years of age in girls. The appreciable development continued in softball throwing even af ter twelve years of age in boys.2. The effect of practice on throwing ability was greatest at seven or eight years old boys, and at eight to ten years old girls. This corresponded well with the age ranges in which throwing distance was increasing most rapidly. In junior high school boys, on the other hand, even though marked development could be seen as age increased, little effect of practice could be seen.3. The effect of practice on throwing distance was seen more in the stable exertion of ability than in the development of the best record. The effect of this type could be shown especially in the younger ages.4. Use of a running approach increased the distance thrown, no matter what the age, for both boys and girls. This difference increased with age in the boys, but not in the girls.5. The distance thrown with running approach improved most in seven and eight year old
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