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The ergonomics of shovelling and shovel design-an experimental study
170
C/in Biomech.
1986;
1: No 3
Multiple regression analysis was applied to determine the relative contribution of these variables to the estimation of injury-proneness as evidenced by previous history of injury and hypermobility traits. Using 9 independent variables, multiple regression yielded a multiple (Ra=O+G40, accounting for over 70%
correlation
coefficient
of the observed variance (R =0.706) in injury scores among the total group of gymnasts. However, a subset of five variables, (weight, mesomorphy. standing lumbar curvature, age and height) yielded a multiple correlation coefficient (R)=OS34 accounting for almost 70% of the observed variance (R’=0.696). This was not significantly different from the larger subset. Using injury classification system of ‘low’, ‘medium’, and ‘high’ risk categories, comparisons were made between predicted and observed injury scores in the respective risk categories. In ‘high’ risk and ‘low’ risk gymnasts, injury scores could be classified correctly with 70% and 79% accuracy respectively, so that relative risk status could be determined from simple physical tests which may be employed by practitioners in the field. Steele VA and White JA. Br J Sports Med 1986: 20: 31-3
ERGONOMICS Postural analysis of the trunk and shoulders simulated real time
in
A new method for analysing and describing the posture of the trunk and shoulders was developed and used to describe the posture of workers performing autoniohile assemhl! operations. The system used a videotape to create ;I permanent record of the job> and ;I personal computer to perform the clerical and ttme-keeping tasks associated with posture analysis. In experiments using an experienced an;ilb\t to evaluate ;I videotape. highly reproducible rt’\ults were obtained. Furthermore. the new sy>tcm required substantially less time than existing pohturc analysis method\ to analyst and reduce postural data. Keyserling
WM.
Ergonomics
spine by the different lifting methods, but the absolute values of the forces remain uncertain because of the uncertainty residing in many of the model’s hypotheses. The method requiring a belt to lift the patient was found to be considerably more strenuous for the spine and also to require a larger amount of work; it should therefore not be recommended as a task for nursing aides. Gagnon M. Sicard C. and Sirois JP. Ergonomics 407-2 1.
Reliability of the psychophysical lifting of liquids by females
1986; 29:
approach to manual
The psychophysical method for setting lifting standards was evaluated by having seven. female college students lift at four Only one different frequencies (1. 3.6 and 12 lifts min-‘). lifting session was performed in a 24 hour period. During the J hour lifting task. subjects were asked to select the amount of water that they believed they could lift comfortably for X hours. Subjects were encouraged to make as many weight chanpes as they needed. Each time the weight was changed the carton was weighed and the time was recorded. At 1.5min intervals. subjects were asked about their degree of confidence (DOC) that the current weight was the maximum acceptable one for an ci hour shift. Oxygen consumption was mc;lhured at 30. 170 and 240 min of the task. The weights chosen by the subjects at 30 min did not differ significantly tram the 4 hour values for frequencies of 1.3 and 6 lifts Ill i n _I. ljowever. at I2 lifts min-’ the weight decreased with II~W such that the -l hour value was 23% lower than the \\clght cho>cn after .iOmin. DOC increased over time and did not differ Ggniticantly between frequencies. Oxygen zon\umption #as unchanged over time and accounted for IY. ‘q 35 and -li.5”,, of 1’0: max for frequencies 1, 3. h and 12 _. Iltt\ mill- ‘. rc\pcctivcly. It was concluded that the p~~c‘hoph~~~cal method ill it> prchcnt form should not he used 1r1\ct liftln~ yt;md;lrd> for frcquencics higher than 6 lifts 111111‘.
IYX(>; 20: 5hY-8.3
Evaluation of forces on the lumbo-sacral joint and assessment of work and energy transfers in nursing aides lifting patients Tasks associated with patient handling may prchcnt nursing aides with some risk of injuring the iumhar spine. The purpose of this study was to estimate the forces at L5/Sl and to assess mechanical work and energy tranhfcr\ in a taA consisting of raising a patient (a 72.6 kg manikin) tram iI chair using three different methods: (A) with the hand\: (B) with the forearms behind the patient’s hack at shoulder level: and (C) with a belt held at waist level. Six male huhjecth took part in the experiment. Spinal forces were estimated from ;I static and planar mathematical model used in conjunction with cinematography techniques. a force platform and EM<; recordings. External forces and the internal forces (compression and shear at LS/Sl) were determined from free-body diagrams and static equations. The model was analysed for its sensitivity in estimating pattern> of EMG forces. intra-discal and musculo-ligamentous forceb. intraabdominal pressure and inertial forces. The model wab found to discriminate between the relative demands imposed on the
The ergonomics of shovelling experimental study
and shovel design-an
In bpitc of increased automation. there is still a need for cr~onomically designed milnual tools in the modern consumer and industrial environment. For example. many \tudiea have examined the work physiology involved in \hovclling. but few have referred to the shovel-design paramctrr\ needed to make the task more efticicnt. To this end. ii two-phase experimental study examined the effects of the followlng parameters: lift angle, the size and shape of the blade, the hollow- and the closed-hack design. the handle length on hhovelling performance. the energy expenditure. the predicted low-back compressive force\ and the subjective rating5 of perceived exertion. The results indicated the following recommendations in shovel design: ;I lift angle of approximately 3P. a large. square-point blade for shovelling, ;I round-point blade for digging. ;I hollow-back construction to reduce weight, ;I solid socket for strength in heavy duty u\es. a step for digging in hard soil and a long tapered handle. Fricvalds A. Ergonomics
19X6; 29: IY-30
C/in Biomech.
1986;
1: No 3
Multiple regression analysis was applied to determine the relative contribution of these variables to the estimation of injury-proneness as evidenced by previous history of injury and hypermobility traits. Using 9 independent variables, multiple regression yielded a multiple (Ra=O+G40, accounting for over 70%
correlation
coefficient
of the observed variance (R =0.706) in injury scores among the total group of gymnasts. However, a subset of five variables, (weight, mesomorphy. standing lumbar curvature, age and height) yielded a multiple correlation coefficient (R)=OS34 accounting for almost 70% of the observed variance (R’=0.696). This was not significantly different from the larger subset. Using injury classification system of ‘low’, ‘medium’, and ‘high’ risk categories, comparisons were made between predicted and observed injury scores in the respective risk categories. In ‘high’ risk and ‘low’ risk gymnasts, injury scores could be classified correctly with 70% and 79% accuracy respectively, so that relative risk status could be determined from simple physical tests which may be employed by practitioners in the field. Steele VA and White JA. Br J Sports Med 1986: 20: 31-3
ERGONOMICS Postural analysis of the trunk and shoulders simulated real time
in
A new method for analysing and describing the posture of the trunk and shoulders was developed and used to describe the posture of workers performing autoniohile assemhl! operations. The system used a videotape to create ;I permanent record of the job> and ;I personal computer to perform the clerical and ttme-keeping tasks associated with posture analysis. In experiments using an experienced an;ilb\t to evaluate ;I videotape. highly reproducible rt’\ults were obtained. Furthermore. the new sy>tcm required substantially less time than existing pohturc analysis method\ to analyst and reduce postural data. Keyserling
WM.
Ergonomics
spine by the different lifting methods, but the absolute values of the forces remain uncertain because of the uncertainty residing in many of the model’s hypotheses. The method requiring a belt to lift the patient was found to be considerably more strenuous for the spine and also to require a larger amount of work; it should therefore not be recommended as a task for nursing aides. Gagnon M. Sicard C. and Sirois JP. Ergonomics 407-2 1.
Reliability of the psychophysical lifting of liquids by females
1986; 29:
approach to manual
The psychophysical method for setting lifting standards was evaluated by having seven. female college students lift at four Only one different frequencies (1. 3.6 and 12 lifts min-‘). lifting session was performed in a 24 hour period. During the J hour lifting task. subjects were asked to select the amount of water that they believed they could lift comfortably for X hours. Subjects were encouraged to make as many weight chanpes as they needed. Each time the weight was changed the carton was weighed and the time was recorded. At 1.5min intervals. subjects were asked about their degree of confidence (DOC) that the current weight was the maximum acceptable one for an ci hour shift. Oxygen consumption was mc;lhured at 30. 170 and 240 min of the task. The weights chosen by the subjects at 30 min did not differ significantly tram the 4 hour values for frequencies of 1.3 and 6 lifts Ill i n _I. ljowever. at I2 lifts min-’ the weight decreased with II~W such that the -l hour value was 23% lower than the \\clght cho>cn after .iOmin. DOC increased over time and did not differ Ggniticantly between frequencies. Oxygen zon\umption #as unchanged over time and accounted for IY. ‘q 35 and -li.5”,, of 1’0: max for frequencies 1, 3. h and 12 _. Iltt\ mill- ‘. rc\pcctivcly. It was concluded that the p~~c‘hoph~~~cal method ill it> prchcnt form should not he used 1r1\ct liftln~ yt;md;lrd> for frcquencics higher than 6 lifts 111111‘.
IYX(>; 20: 5hY-8.3
Evaluation of forces on the lumbo-sacral joint and assessment of work and energy transfers in nursing aides lifting patients Tasks associated with patient handling may prchcnt nursing aides with some risk of injuring the iumhar spine. The purpose of this study was to estimate the forces at L5/Sl and to assess mechanical work and energy tranhfcr\ in a taA consisting of raising a patient (a 72.6 kg manikin) tram iI chair using three different methods: (A) with the hand\: (B) with the forearms behind the patient’s hack at shoulder level: and (C) with a belt held at waist level. Six male huhjecth took part in the experiment. Spinal forces were estimated from ;I static and planar mathematical model used in conjunction with cinematography techniques. a force platform and EM<; recordings. External forces and the internal forces (compression and shear at LS/Sl) were determined from free-body diagrams and static equations. The model was analysed for its sensitivity in estimating pattern> of EMG forces. intra-discal and musculo-ligamentous forceb. intraabdominal pressure and inertial forces. The model wab found to discriminate between the relative demands imposed on the
The ergonomics of shovelling experimental study
and shovel design-an
In bpitc of increased automation. there is still a need for cr~onomically designed milnual tools in the modern consumer and industrial environment. For example. many \tudiea have examined the work physiology involved in \hovclling. but few have referred to the shovel-design paramctrr\ needed to make the task more efticicnt. To this end. ii two-phase experimental study examined the effects of the followlng parameters: lift angle, the size and shape of the blade, the hollow- and the closed-hack design. the handle length on hhovelling performance. the energy expenditure. the predicted low-back compressive force\ and the subjective rating5 of perceived exertion. The results indicated the following recommendations in shovel design: ;I lift angle of approximately 3P. a large. square-point blade for shovelling, ;I round-point blade for digging. ;I hollow-back construction to reduce weight, ;I solid socket for strength in heavy duty u\es. a step for digging in hard soil and a long tapered handle. Fricvalds A. Ergonomics
19X6; 29: IY-30