Automation of Workplace Lifting Hazard Assessment for Musculoskeletal Injury Prevention

OBJECTIVES: Existing methods for practically evaluating musculoskeletal exposures such as posture and repetition in workplace settings have limitations. We aimed to automate the estimation of parameters in the revised United States National Institute for Occupational Safety and Health (NIOSH) lifting equation, a standard manual observational tool used to evaluate back injury risk related to lifting in workplace settings, using depth camera (Microsoft Kinect) and skeleton algorithm technology. METHODS: A large dataset (approximately 22,000 frames, derived from six subjects) of simultaneous lifting and other motions recorded in a laboratory setting using the Kinect (Microsoft Corporation, Redmond, Washington, United States) and a standard optical motion capture system (Qualysis, Qualysis Motion Capture Systems, Qualysis AB, Sweden) was assembled. Error-correction regression models were developed to improve the accuracy of NIOSH lifting equation parameters estimated from the Kinect skeleton. Kinect-Qualysis errors were modelled using gradient boosted regression trees with a Huber loss function. Models were trained on data from all but one subject and tested on the excluded subject. Finally, models were tested on three lifting trials performed by subjects not involved in the generation of the model-building dataset. RESULTS: Error-correction appears to produce estimates for NIOSH lifting equation parameters that are more accurate than those derived from the Microsoft Kinect algorithm alone. Our error-correction models substantially decreased the variance of parameter errors. In general, the Kinect underestimated parameters, and modelling reduced this bias, particularly for more biased estimates. Use of the raw Kinect skeleton model tended to result in falsely high safe recommended weight limits of loads, whereas error-corrected models gave more conservative, protective estimates. CONCLUSIONS: Our results suggest that it may be possible to produce reasonable estimates of posture and temporal elements of tasks such as task frequency in an automated fashion, although these findings should be confirmed in a larger study. Further work is needed to incorporate force assessments and address workplace feasibility challenges. We anticipate that this approach could ultimately be used to perform large-scale musculoskeletal exposure assessment not only for research but also to provide real-time feedback to workers and employers during work method improvement activities and employee training.

El peso transportado en las mochilas escolares: Un estudio en cuatro escuelas de la región metropolitana de Buenos Aires, Argentina / A study concerning how much weight schoolchildren carry in their bags, involving four schools in the metropolitan area of Buenos Aires, Argentina

RESUMEN Objetivo Determinar el peso transportado del equipaje escolar (en valores absolutos y relativos) y la distancia caminada en los trayectos hogar-escuela, en escolares de cuatro escuelas de la región metropolitana de Buenos Aires. Métodos Se estudiaron 751 alumnos (394 varones y 357 mujeres, de 9 a 18 años) de niveles primario (4to. a 6to. grados), y secundario (1ro. a 3er. años) de tres escuelas de gestión privada y una pública. Se midieron los pesos corporal y del equipaje escolar, y se indagó sobre la distancia desde la escuela al hogar, y sobre las cuadras caminadas en este trayecto. Se realizó un análisis descriptivo y contrastes según género, nivel educativo, tipo de escuela y grados y años cursados. Se verificaron posibles asociaciones entre variables. Se dividió al grupo en dos: quienes transportaban menos del 10 % de su peso corporal, y los que acarreaban el 10 % (considerado como valor crítico) y más, calculándose las frecuencias según tipo de equipaje utilizado. Resultados El 68 % de los evaluados transporta un peso por encima del 10 % del peso corporal (P42=10,13 %), siendo del 66 % para varones (P44 = 10,12 %) y 60 % para mujeres (P40=10,2 %). En escuelas privadas se acarrearon mayores pesos que en públicas (p<0,05); y en ambos niveles educativos los alumnos de cursos inferiores transportaron pesos superiores que los de grados superiores (p<0,05). Conclusiones La mayoría de los alumnos transporta pesos relativos por encima de las recomendaciones, siendo las mujeres las más perjudicadas. Los más pequeños cargan pesos absolutos y relativos mayores.

ABSTRACT Objective Determining the weight children carry in their bags to school (absolute and relative values) and the distance walked during home-school routes, involving students from four schools in the metropolitan area of Buenos Aires. Method The study involved 751 primary (4th to 6th grades) and secondary (1st to 3rd years) level students who were attending three private schools and one public one. Body and bag weights were measured and the children were asked about the distance (in blocks) they walked from school to home. The study involved a descriptive analysis and contrasted the students by gender, educational level, type of school and grade or year. Possible associations between variables were ascertained. The group was divided into those carrying bags weighing less than 10% of their body weight and those who carrying 10% (considered a critical value) and more; frequencies were calculated by the type of bag being used. Results 68% of the sample were carrying 10% or more of their body weight (P42=10.13%): 66% in male (P44=10.12%) and 60% in female children (P40=10.2%). Private school students carried more weight than public school children (p<0.05) and younger students carried a greater weight than older students (p<0.05) in both educational levels. Conclusions Most children were carrying relative weights well above that recommended and female students were most affected. Younger students carried higher absolute and relative weights.

Injury risks and affecting factors of spinal loads for caregiver’s manual patient handling tasks / 医用生物力学

Objective To assess the injury risks and affecting factors of spinal loads at L5/S1 joint for caregivers during manual patient-handling tasks, so as to find a suitable handling way to effectively reduce such risks. Methods Kinetic data were collected from nine female caregivers performing six patient handling tasks on three agent ‘patients’ with different weight. Peak L5/S1 force was calculated based on a multi-segment three-dimensional model to investigate the characteristics of injury risks, and the correlations between the peak L5/S1 force and six affecting factors were specifically analyzed. Results Peak compression of the tasks all exceeded the safe thresholds of 3.4 kN; Peak anterior-posterior force for those repositioning tasks were above the threshold of 0.5 kN. Different tasks showed different biomechanical characteristics for risk of injury and affecting factors, and there was a significant correlation between the L5/S1 loads and the moving distance of center of gravity, and the ground reaction force as well (P<0.01). Conclusions Manual patient handling tasks could cause different injury risks by high loads on spinal low back. Decreasing the range of motion of the whole body and avoiding jerk movement during the patient handling tasks would help caregiver to reduce the injury risks.

An Epidemiological Aspect of Low Back Injuries in Some Industries of Pusan Area / 대한정형외과학회잡지

An epidemiological investigation of 878 workers(male 812, female 66) who suffered from low back injury(LBI) in some workplace of Pusan city from January 1 to December 31 in 1992 was carried out to obtain the various informations of the prevention and management in the occupational low back pain(LBP). The results were summarized as follows: 1. The mean age of LBP workers was 39.3±10.4(18-67) in male 48.5±12.6(21-69) in female workers. And the most common age groups were the 4th decade in male and the 6th decade in female workers. 2. In the frequency distribution of LBI according to the kind of industry, manufacturing industry was most frequent, and industry of construction, transport-storage-communication were the next in order. Among manufacturing industry, LBI of metallic products and machinery was the most frequent. 3. The occupational frequency of LBP was technical worker, monotonous worker, driver of automobile, driver of heavy equipment and office worker in order. 4. The cumulative percentage of LBI was 6.9% at the first day of employment and 90.8% until 10 years after employment. 5. The mean working duration from employment to onset of injury was 1081 days(about 2.9 years) and the working duration according to occupation was the shortest in driver of heavy equipment(502 days) and longest in office worker(1982 days). 6. The careless handling of object was the most common cause of LBI, and fall down, slip down, collision and traffic accidents were the next in order. 7. The most common cause of LBI according to occupation was traffic accident in driver of automobile, fall down in driver of heavy equipment and careless handling of object in office worker respectively. 8. The case of localized LBI were 517(58.9%) and the cases of LBI combined with other injuries, such as head, neck, trunk, arm or leg, were 361(41.1%) 9. Lumbar sprain was the most frequent diagnosis of LBI, and Herniated Nucleus Pulposus(HNP) and lumbar fracture were the next in order. 10. In multiple injuries, LBI combined with multiple body injury was the most frequent, and the next was LBI combined with arm and leg, with trunk, with head and with neck in order. 11. LBI combined with multiple body injury was the main injury in fall down, slip down and traffic accident, and lumbar sprain was the main injury in careless handling of object.

Sociomedical Survey on the Occupational Low Back Injuries of the Some Workers in Pusan Area / 예방의학회지

This survey was performed to obtain the basic information for the prevention and management of occupational low back injury(LBI). The subjects of this survey were 952 workers(male, 892;female, 60) who had taken occupational LBI in some industries of Pusan area from January 1 to December 31, 1991. Observation period was 2.6 years from the beginning to the end of medical treatment. The obtained results were summarized as follows; 1. The proportion of LBI workers was 15.9% of the workers who had taken any occupational injuries and 0.32% of all workers in this surveyed area. 2. 8.0% of the workers had taken LBI on the 1st day of employment and 55.2% of the workers were within one year, 91.4% of the workers were within 10 years according to cumulative frequency distribution. 3. Handling of heavy objects was the most common cause of LBI(32.0%) and fall down(26.9%) and slip down(16.3%) were the next in order. 4. The most common causes of both lumbar sprain and HNP were handling of heavy objects and that of lumbar fracture was fall down. 5. The mean duration for medical treatment of LBI workers was 143 days. 6. The total direct compensation cost for LBI workers was 6,736 million Won and the proportion of medical, resting, disability compensation costs were 25.0%, 37.0%, 38.0% respectively. 7. The percentages of retreated workers and disabled workers were 11.9%(113 persons) and 22.9%(218 persons) of total LBI workers respectively.