Lifting and overstraining are major causative factors related to musculoskeletal injuries and low back pain. A great number of work-related injuries arise from the handling and/or mishandling of materials. Hence there is a need to quantify risk factors in situ and develop guidelines for safe lifting practises in industry. The aim of this study was to make appropriate in situ quantification, within a commercial warehouse, of the stresses and physical demands imposed on the worker when performing two handed lifts in the sagittal plane. The performance of employees was assessed under normal working conditions through an observational methodology of data collection. Task performance evaluation was based on detailed measurement of all containers handled, an activity and time analysis, and the 'Work Practices Guide to Manual Lifting’ (NIOSH, 1981) which was used as the primary guide to developing theoretical recommendations to probable MMH risk factors for the workers involved. Of the 191 tasks analysed 103 were deemed unsuitable. Appropriate task factor adjustments were made where necessary to both the frequency and Hfactors (horizontal distance between the centre of gravity of the container and that of the worker) in order to reduce the risk factor for the workers

"Back injuries have consistently been the most common types of injuries suffered by people at work. They have been a significant worker injury problem in most, if not all, industrialised countries for many years and manual handling has long been established as a significant task related back injury causal factor.[...] This research project established that the manufacturers of the jet airlines used by the airlines in this study had not previously been acquainted with the issue of baggage handler back injuries.[...] This study also canvassed the opinion of airline safety professionals and airline baggage handlers concerning baggage handling tasks and working environment related causal factors. [...] A major focus of this research project was also to measure the effect of ACE and Sliding Carpet, two commercially available retro-fit baggage systems, on the risk of back injuries to baggage handlers stacking baggage within Boeing B737 narrow-body aircraft." / Doctor of Philosophy

"Back injuries have consistently been the most common types of injuries suffered by people at work. They have been a significant worker injury problem in most, if not all, industrialised countries for many years and manual handling has long been established as a significant task related back injury causal factor.[...] This research project established that the manufacturers of the jet airlines used by the airlines in this study had not previously been acquainted with the issue of baggage handler back injuries.[...] This study also canvassed the opinion of airline safety professionals and airline baggage handlers concerning baggage handling tasks and working environment related causal factors. [...] A major focus of this research project was also to measure the effect of ACE and Sliding Carpet, two commercially available retro-fit baggage systems, on the risk of back injuries to baggage handlers stacking baggage within Boeing B737 narrow-body aircraft." / Doctor of Philosophy

Pushing and pulling research has yet to fully elucidate the demands placed on manual workers despite established epidemiological links to musculoskeletal disorders. The current study therefore aimed to quantify biomechanical and perceptual responses of male operators to dynamic pushing and pulling tasks. Three common push/pull techniques (pushing, one handed and two handed pulling) were performed at loads of 250kg and 500kg using an industrial pallet jack in a laboratory environment. Thirty six healthy male subjects (age: 21 ±2 years, stature: 1791 ±43 mm and body mass: 77 ±10 kg) were required to perform six loaded experimental and two unloaded control conditions. Hand force exertion, muscle activity and gait pattern responses were collected during 10m push/pull trials on a coefficient controlled walkway; body discomfort was assessed on completion of the condition. Horizontal hand force responses were significantly (p<0.05) affected by load, with a linear relationship existing between the two. This relationship is determined by specific environmental and trolley factors and is context specific, depending on factors such as trolley maintenance and type of flooring. Hand force exertion responses were tenuously affected by technique at higher loads in the initial and sustained phases, with pushing inducing the greatest hand forces. Comparison of the motion phases revealed significant differences between all three phases, with the initial phase evidencing the greatest hand forces. Muscle activity responses demonstrated that unloaded backward walking evoked significantly higher muscle activation than did unloaded forward walking whilst increased muscular activity during load movement compared to unloaded walking was observed. However increasing load from 250kg to 500kg did not significantly impact the majority of muscle activity responses. When considering technique effects on muscle activity, of the significant differences found, all indicated that pushing imposed the least demand on the musculoskeletal system. Gait pattern responses were not significantly affected by load/technique combinations and were similar to those elicited during normal, unloaded walking. Perceptually, increased load led to increased perception of discomfort while pushing resulted in the least discomfort at both loads. From these psychophysical responses, the calves, shoulders and biceps were identified as areas of potential musculoskeletal injury, particularly during one and two handed pulling. Pushing elicited the highest hand forces and the lowest muscle activity responses in the majority of the conditions whilst psychophysical responses identified this technique as most satisfactory. Current results advocate the use of pushing when moving a load using a wheeled device. Suitability of one and two handed pulling remains contradictory, however results suggest that one handed pulling be employed at lower loads and two handed pulling at higher loads.

There is anecdotal and scientific evidence to suggest that schoolbag carriage is associated with musculoskeletal discomfort (MSD) and possibly long-term back pain. Thus schoolbag carriage is an area of concern for students, parents and both education and health professionals. A schoolbag weight limit of 10% of body weight (BW) is currently recommended. However, it is based on subjective observations rather than objective findings and does not consider other aspects of schoolbag carriage such as schoolbag design and adjustment or carriage patterns. Five studies were conducted in order to determine the effects on students' responses to schoolbag carriage of schoolbag design, adjustment, carriage duration and weight. Backpack design had a significant effect on reported musculoskeletal discomfort and choice of backpack. Schoolbag hip-belt and shoulder strap adjustment and weight significantly affected shoulder strap tension forces and shoulder interface pressure in simulated schoolbag carriage. Using activity monitoring, school students were found to spend approximately two hours carrying their schoolbags each day. This usually comprised 11-15 times per day of 8-9 minutes of carriage. Using this temporal pattern information, 16 boys (13-14 years) were exposed to a simulated school day using schoolbags weighing 0, 5, 10, 12.5 and 15% BW and an additional condition of 10% BW with tighter shoulder straps. Posture, rating of perceived exertion (RPE), muscular strain and reported ability to walk and balance were significantly affected when schoolbag load reached 10% BW. However, despite these findings, the magnitude of self reported muscular strain and MSD suggested that 15% BW may be too heavy for school students. Thus, 10% BW may be an appropriate upper schoolbag weight limit for a typical school day. Using a psychophysical approach the mean (standard deviation) maximum acceptable schoolbag weight (MASW) selected by 16 school boys (13-14 years) was 10.4(3.8) %BW. This finding agrees with the findings of the previous study and supports the current schoolbag weight recommendation of 10% BW. The results of the five studies can be used in developing schoolbag carrying guidelines to help reduce the prevalence of MSD amongst school students.

The focus of this study investigates the effect backpack weight has on the height of middle school students. It provides data about the effects of backpack weight on height that has not previously been determined. This study aims to contribute information to a growing body of evidence which supports the limitation of backpack weight for children to be no more than 10% of body weight.

Lau Tsz Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 57-66). / Text in English; abstracts in English and Chinese. / Lau Tsz Chung. / Acknowledgement --- p.i / Abstract --- p.ii / Table of contents --- p.v / List of Figures --- p.viii / List of Tables --- p.x / Introduction --- p.1 / Background --- p.1 / Statement of Problem --- p.3 / Research Question --- p.4 / Significance of the Study --- p.4 / Theoretical Contribution --- p.4 / Practical Contribution --- p.5 / Review of Literature --- p.7 / Load carrying on Level Ground --- p.7 / Research Method Involved --- p.8 / Modified Gait Pattern During Load Carriage --- p.9 / Trunk Posture --- p.10 / Low Back Pain --- p.11 / Posture and Back Pain --- p.12 / Load Carrying Studies in Children --- p.14 / Stair Walking --- p.15 / Compared with Level Walking --- p.15 / Temporal Characteristics --- p.17 / Kinematics Measurement --- p.18 / Stair Dimensions --- p.19 / Stair Walking with Load Carriage --- p.21 / Physiological Studies --- p.21 / Biomechanical Studies --- p.21 / Methodology --- p.24 / Design --- p.24 / Subject --- p.24 / Instrumentation --- p.25 / Motion Analysis System --- p.25 / School Bag --- p.25 / Experimental Set-up --- p.25 / Procedure --- p.26 / Term Definition --- p.27 / Data Analysis --- p.27 / Results --- p.29 / Ascending Stair --- p.29 / Posture --- p.29 / Effect on Load Weight --- p.29 / Effect on Load Carrying Method --- p.30 / Velocity --- p.30 / Parameters of Lower Extremities --- p.30 / Descending Stair --- p.31 / Posture --- p.31 / Effect on Load Weight --- p.31 / Effect on Load Carrying Method --- p.31 / Velocity --- p.32 / Parameters of Lower Extremities --- p.32 / Trend --- p.32 / Summary --- p.33 / Discussion --- p.35 / Ascending Stair --- p.35 / Posture --- p.35 / Different Load Weights --- p.35 / Different Carrying Methods --- p.39 / Velocity --- p.40 / Descending Stair --- p.42 / Posture --- p.42 / Velocity --- p.46 / Parameters of Lower Extremities --- p.47 / Trend --- p.48 / Back Pain --- p.49 / Recommended Carrying Load Method and Weight for Children --- p.50 / Limitations of the Study --- p.52 / Further Study --- p.53 / Conclusion --- p.56 / References --- p.57 / Appendix --- p.67 / Appendix A - The experimental Set-up --- p.67 / Appendix B - Subject Consent Form --- p.68 / Appendix C - Figures and Tables --- p.71

Thesis (MScEng) Stellenbosch University, 2014 / ENGLISH ABSTRACT: This thesis brings together productivity and risk assessments through innovative design, development and evaluation of a unique system for retrieving and analysing data. In the past, although the link between them is well-documented, these assessments have largely been dealt with as separate antagonist entities. A broad evaluation of the existing traditional and technological support systems has been conducted to identify suitable methodologies along with a common technological platform for automation. The methodologies selected for the productivity and risk assessments were; work sampling and the revised NIOSH lifting equation respectively. The automation of these procedures is facilitated through computer vision and the use of a range imaging Kinect™ camera. The standalone C++ application integrates two tracking approaches to extract real-time positional data on the worker and the work-piece. The OpenNI and OpenCV libraries are used to perform skeletal tracking and image recognition respectively. The skeletal tracker returns positional data on specific joints of the worker, while the image recognition component, a SURF implementation, is used to identify and track a specific work-piece within the capture frame. These tracking techniques are computationally expensive. In order to enable real time execution of the program, Nvidia’s CUDA toolkit and threading building blocks have been applied to reduce the processing time. The performance measurement system is a continuous sampling derivative of work sampling. The speed of the worker’s hand movements and proximity to the work-piece are used to classify the worker in one of four possible states; busy, static, idle, or out of frame. In addition to the worker based performance measures, data relating to work-pieces are also calculated. These include the number of work-pieces processed by a specific worker, along with the average and variations in the processing times. The risk assessment is an automated approach of the revised NIOSH lifting equation. The system calculates when a worker makes and/or breaks contact with the work-piece and uses the joint locations from the skeletal tracker to calculate the variables used in the determination of the multipliers and ultimately the recommended weight limit and lifting index. The final calculation indicates whether the worker is at risk of developing a musculoskeletal disorder. Additionally the information provided on each of the multipliers highlights which elements of the lifting task contribute the most to the risk. The user-interface design ensures that the system is easy to use. The interface also displays the results of the study enabling analysts to assess worker performance at any time in real time. The automated system therefore enables analysts to respond rapidly to rectify problems. The system also reduces the complexity of performing studies and it eliminates human errors. The time and costs required to perform the studies are reduced and the system can become a permanent fixture on factory floors. The development of the automated system opens the door for further development of the system to ultimately enable more detailed assessments of productivity and risk. / AFRIKAANSE OPSOMMING: Produktiwiteit en risiko evaluerings word in hierdie tesis saam hanteer deur die innoverende ontwerp, ontwikkeling en evaluering van 'n unieke stelsel vir die meting en ontleding van data. Alhoewel die skakel tussen hulle goed gedokumenteer is, word hierdie evaluering as afsonderlike antagonistiese entiteite hanteer. 'n Breë studie van die bestaande tradisionele en tegnologiese ondersteuningstelsels is gedoen om toepaslike metodes te identifiseer, om 'n gemeenskaplike tegnologiese platform vir outomatisering daar te stel. Die metodes wat gekies is vir die produktiwiteit en risiko bepalings is onderskeidelik werk monsterneming en die hersiende NIOSH opheffing vergelyking. Die outomatisering van hierdie prosedures word gefasiliteer deur middel van rekenaar visie en die gebruik van 'n Kinect™ 3D kamera. Die selfstandige C++ program integreer ‘n dubbelvolgings benadering om in reële tyd posisionele data van die werker en die werk-stuk te kry. Die OpenNI en OpenCV biblioteke word onderskeidelik gebruik om skeletale volging en beeld erkenning uit te voer. Die skeletale volger bepaal posisionele data van spesifieke gewrigte van die werker, terwyl die beeld erkenning komponent, 'n SURF implementering gebruik om 'n spesifieke werk-stuk binne die opname raam te identifiseer en te volg. Hierdie volgings tegnieke is berekenings intensief. Om werklike tyd uitvoering van die program te verseker, is Nvidia se CUDA gereedskapstel en liggewig boublokke geimplementeer. Die produktiwiteit meting-stelsel is 'n aaneenlopende monsterneming benadering van werk monsterneming. Die spoed van die werker se handbewegings en nabyheid aan die werkstuk word gebruik om die werker te klassifiseer as in een van vier moontlike toestande; besig, staties, onaktief of buite die raam. Benewens die werker gebaseerde metings, word daar ook data oor werkstukke bereken. Dit sluit in die aantal werkstukke verwerk deur 'n spesifieke werker, sowel as die gemiddelde en variasie in verwerkings tye. Die risiko-berekening is 'n outomatiese benadering van die hersiende NIOSH opheffing vergelyking. Die stelsel bereken wanneer die werker kontak maak en/of breek met die werkstuk en maak gebruik van die gewrigsposisies wat die skeletale volger aandui om die veranderlikes wat in die vermenigvuldigers gebruik word te bepaal. Die vermenigvuldigers word gebruik om die aanbevole maksimum gewig en die opheffing indeks te bereken. Die opheffing indeks dui aan of daar ‘n risiko vir die werker is om muskuloskeletale versteuring te ontwikkel. Benewens dui die vermenigvuldigers aan watter elemente die grootste bydra tot die risiko van die opheffingstaak maak. Die gebruiker-koppelvlak-ontwerp verseker dat die stelsel maklik is om te gebruik. Die koppelvlak vertoon ook die resultate van die studie sodat ontleders op enige tyd werker prestasie kan evalueer in reële tyd. Die outomatiese stelsel stel dus ontleders in staat om vinnig te reageer sodat probleme reggestel kan word. Die stelsel verminder ook die kompleksiteit vir die uitvoering van studies en dit elimineer menslike foute. Die tyd en koste vereis om die studie te doen, word verminder en die stelsel kan ‘n permanente instelling op fabriekvloere geword. Die ontwikkeling van die outomatiese stelsel maak die deur oop vir verdere ontwikkeling van die stelsel om uiteindelik daartoe te lei dat meer gedetailleerde evaluering van produktiwiteit en risiko bepaal kan word.

The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory The focus of this investigation was an analysis of the work demands being placed on South African automotive industry workers as there is a recognised problem with regard to the prevalence of musculoskeletal disorders (MSDs). Preliminary work was conducted to highlight the dominant risks and areas which elicited higher numbers of MSDs within the chosen automotive plant. An area of concern was highlighted through medical record analysis and the use of risk assessment tools, thereby prioritising the need for ergonomic intervention. In particular, the effects of varying restricted and overhead work heights on the biomechanical, physiological and psychophysical responses of an individual were investigated. Twenty-eight subjects were required to complete sixteen conditions. The conditions consisted of the adoption of restricted and upright overhead static postures, with half requiring the holding of four kilograms of weight in the hands and the remaining eight conditions having no weight. Testing was carried out using an electromyography unit, ergospirometer and a perceptual Body Discomfort Map and Scale. This involved a habituation and testing session. The results of the testing revealed the biomechanical and physiological responses were dependant on the change in height. Body discomfort was also shown to be variable over the changing height conditions. This indicates that there is a significant effect of height on an individual’s responses during overhead work. The extreme restricted (-200mm and -100mm) and upright (+300mm and +400mm) overhead conditions within this study were limiting, as they elicited the highest muscle activation, physiological responses and body discomfort ratings. Positions that are preferable to adopt, which were identified from the results in this study, indicate conditions closer to head height (0mm and +100mm) were favourable. The results therefore illustrate how awkward working postures during work are likely to elicit higher demands from an individual, which could lead to an increased risk for the development of a musculoskeletal disorder. The added factor of weight elicited significant results over all variables, excluding a respiratory individual.

Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. / Name on Graduation Programme: Bassey-Duke, Elizabeth Missan