Comparisons of Trunk Motions and Low Back Injury Risk between Alternative Hotel Room Cleaning Methods.

Hotel room cleaners frequently report job-related pain, with high rates of work-related musculoskeletal disorder injuries established for this group of workers. Surprisingly, there is limited published research documenting the impact of interventions to reduce ergonomic-related injury risks specific to hotel room cleaners' job tasks. In this study focused on hotel bathroom-cleaning and furniture-dusting tasks, twelve experienced hotel room cleaners used their standard method and a risk-reduction method-a tool with a handle that could extend, to perform these tasks. The female study participants' average age was 45.3 (SD 8.7) years with an average of 10 years of work experience as cleaners (range: 0.8-26.0 years). Trunk kinematics and a low back injury risk assessment were measured using the Lumbar Motion Monitor. All study metrics were significantly reduced when cleaning tasks involved use of adjustable, long-handled tools (p < 0.05). This study demonstrated that commonly available cleaning and dusting tools with extendable handles can significantly reduce low back injury risk among hotel room cleaners and potentially reduce injury risk to other body parts known to be the site of musculoskeletal disorders in this workforce. The study findings suggest that cleaning or housekeeping jobs in other industries where these same tasks are performed could benefit from use of extended-handle tools like those investigated here.

Quantifying the effectiveness of static and dynamic insoles in reducing the tibial shock experienced during walking.

Many individuals work in jobs that require them to spend much of their day walking. There is evidence to suggest that shoe insoles may reduce the lower extremity discomfort for these workers. This study compared the effects of static and dynamic shoe insoles on lower extremity forces when walking at different speeds. Tibial acceleration (a.k.a. tibial shock) was assessed bilaterally in 30 participants who walked in both athletic shoes and work boots without any additional insole, with additional static insoles, and with additional dynamic insoles. The participants walked a prescribed course at a "slow", "normal", and "fast" pace. With both shoe types, there were significant reductions in tibial shock values when insoles were used. With the work boots, the dynamic insole further reduced tibial shock relative to the static insole. The significant interactions show that the differences between insole conditions become greater with faster walking speeds.

Re-thinking floor mat design from an ergonomics perspective: Can a two-part mat system reduce biomechanical loads during normal mat handling tasks?

Floor mats are commonplace in commercial buildings, particularly in entry ways. These mats are routinely handled by delivery personnel as the mats are picked up for cleaning and clean mats are deployed. A new two-part mat design, which eliminates the need to move the rubber base during mat change operations, was hypothesized to reduce the physical demands on delivery personnel. Electromyographic data from back and shoulder muscles and spinal kinematics were obtained as 12 volunteers simulated mat selection, mat deployment, and mat pick-up tasks. Other factors considered in this study included mat size, pick-up method, and mat textile orientation during deployment. Results indicated that the two-part design reduced muscle activation levels across all tasks. Biomechanical benefits were also found when the mats were picked-up using a kick-fold as opposed to hand-fold method and when mats were deployed with the textile component rolled towards the inside of the roll.

An electromyographic and kinematic comparison between an extendable conveyor system and an articulating belt conveyor used for truck loading and unloading tasks.

Many retail distribution centers (DCs) manually load and unload boxes into or out of trailers and shipping containers. This study investigated whether an articulating belt conveyor with a height adjustable platform, positioned at the end of an extendable conveyor, significantly reduces shoulder and back muscle loading and the spine kinematics associated with these tasks. Electromyographic and kinematic data were collected from eight volunteer employees as trailers at a shoe DC were unloaded and from nine volunteer employees as trailers at an apparel DC were loaded. Participants in this repeated measures study handled boxes with a conventional powered extendable conveyor system and with the articulating belt conveyor positioned at the end of the extendable conveyor. Bilaterally the normalized activation levels of the erector spinae and anterior deltoid muscles were reduced when loading and unloading boxes with the articulating belt conveyor. Spine movement speeds were also reduced with the articulating conveyor.

Comparisons of tibial accelerations when walking on a wood composite vs. a concrete mezzanine surface.

Mezzanine surfaces can be made from concrete, bar grate, or composite materials. Anecdotal data indicate that mezzanines in distribution centers made from composite materials, due to their increased compliance, may be a more comfortable working surface. Prior research suggested that a measure of tibial shock, peak tibial acceleration, could potentially discriminate the biomechanical differences between these surfaces. The objective of this study was to quantify differences in tibial accelerations as 27 people walked on mezzanines constructed from concrete and a wood composite material. Accelerometers were attached bilaterally to the shins of volunteers, and data were collected as they walked 30.5 m on each surface at their normal walking speed, a faster-than-normal walking speed, and a slower-than-normal walking speed. Peak acceleration values obtained from the leg with the highest values were compared. On average, the peak acceleration values were 5% higher on the concrete mezzanine as compared with the wood composite mezzanine (p = .036). These findings suggest that individuals working on mezzanines in distribution centers constructed from composite surfaces would potentially experience less discomfort associated with long exposure periods on these surfaces.

Shoulder muscle fatigue during repetitive tasks as measured by electromyography and near-infrared spectroscopy.

OBJECTIVE: The objective of this study was to quantify shoulder muscle fatigue during repetitive exertions similar to motions found in automobile assembly tasks. BACKGROUND: Shoulder musculoskeletal disorders (MSDs) are a common and costly problem in automotive manufacturing. METHOD: Ten subjects participated in the study. There were three independent variables: shoulder angle, frequency, and force. There were two types of dependent measures: percentage change in near-infrared spectroscopy (NIRS) measures and change in electromyography (EMG) median frequency. The anterior deltoid and trapezius muscles were measured for both NIRS and EMG. Also, EMG was collected on the middle deltoid and biceps muscles. RESULTS: The results showed that oxygenated hemoglobin decreased significantly due to the main effects (shoulder angle, frequency, and force). The percentage change in oxygenated hemoglobin had a significant interaction attributable to force and repetition for the anterior deltoid muscle, indicating that as repetition increased, the magnitude of the differences between the forces increased. The interaction of repetition and shoulder angle was also significant for the percentage change in oxygenated hemoglobin. The median frequency decreased significantly for the main effects; however, no interactions were statistically significant. CONCLUSIONS: There was significant shoulder muscle fatigue as a function of shoulder angle, task frequency, and force level. Furthermore, percentage change in oxygenated hemoglobin had two statistically significant interactions, enhancing our understanding of these risk factors. APPLICATION: Ergonomists should examine interactions of force and repetition as well as shoulder angle and repetition when evaluating the risk of shoulder MSDs.

Biomechanical, psychosocial and individual risk factors predicting low back functional impairment among furniture distribution employees.

BACKGROUND: Biomechanical, psychosocial and individual risk factors for low back disorder have been studied extensively however few researchers have examined all three risk factors. The objective of this was to develop a low back disorder risk model in furniture distribution workers using biomechanical, psychosocial and individual risk factors. METHODS: This was a prospective study with a six month follow-up time. There were 454 subjects at 9 furniture distribution facilities enrolled in the study. Biomechanical exposure was evaluated using the American Conference of Governmental Industrial Hygienists (2001) lifting threshold limit values for low back injury risk. Psychosocial and individual risk factors were evaluated via questionnaires. Low back health functional status was measured using the lumbar motion monitor. Low back disorder cases were defined as a loss of low back functional performance of -0.14 or more. FINDINGS: There were 92 cases of meaningful loss in low back functional performance and 185 non cases. A multivariate logistic regression model included baseline functional performance probability, facility, perceived workload, intermediated reach distance number of exertions above threshold limit values, job tenure manual material handling, and age combined to provide a model sensitivity of 68.5% and specificity of 71.9%. INTERPRETATION: The results of this study indicate which biomechanical, individual and psychosocial risk factors are important as well as how much of each risk factor is too much resulting in increased risk of low back disorder among furniture distribution workers.

Musculoskeletal disorder risk during automotive assembly: current vs. seated.

Musculoskeletal disorder risk was assessed during automotive assembly processes. The risk associated with current assembly processes was compared to using a cantilever chair intervention. Spine loads and normalized shoulder muscle activity were evaluated during assembly in eight regions of the vehicle. Eight interior cabin regions of the vehicle were classified by reach distance, height from vehicle floor and front to back. The cantilever chair intervention tool was most effective in the far reach regions regardless of the height. In the front far reach regions both spine loads and normalized shoulder muscle activity levels were reduced. In the middle and close reach regions spine loads were reduced, however, shoulder muscle activity was not, thus an additional intervention would be necessary to reduce shoulder risk. In the back far reach region, spine loads were not significantly different between the current and cantilever chair conditions. Thus, the effectiveness of the cantilever chair was dependent on the region of the vehicle.

Neurologically intact survival in a porcine model of cardiac arrest: manual cardiopulmonary resuscitation vs. LifeBelt cardiopulmonary resuscitation.

OBJECTIVE: To compare the LifeBelt (Deca-Medica, Inc., Columbus, OH), a novel cardiopulmonary resuscitation (CPR) device, with manual CPR on the outcome of neurologically intact survival in a porcine model of cardiac arrest. METHODS: Twenty-two adolescent swine were randomized by permuted block design to resuscitation using LifeBelt (n = 12) or manual CPR (n = 10). The animals were instrumented with right atrial and aortic pressure catheters while they were under general anesthesia with isoflurane and nitrous oxide. Ventricular fibrillation (VF) was induced with a bipolar pacing catheter placed in the right ventricle. After 7 minutes of untreated VF, chest compressions with either LifeBelt or manual CPR were initiated along with standard Advanced Cardiac Life Support. Survivors were assigned a neurologic score using the neurologic deficit score and the cerebral performance category (CPC) score at 24, 48, and 72 hours following resuscitation by a veterinarian blinded to treatment allocation. RESULTS: There were no significant differences in prearrest hemodynamic parameters or in important resuscitation variables between the groups. One of 12 of the LifeBelt animals failed to achieve return of spontaneous circulation (0.08, 95% confidence interval [CI] 0.002-0.38). The remaining 11 had a neurologic deficit score of 0 and a CPC score of 1, indicating normal neurologic function. All of the manual CPR animals survived. One of 10 manual CPR survivors (0.10, 95% CI 0.003-0.45) had a neurologic deficit score of 260 and a CPC score of 3, indicating moderate disability, while the remaining animals had a neurologic deficit score of 0 and a CPC score of 1. CONCLUSIONS: In this porcine model of cardiac arrest, we did not detect significant differences in neurologically intact survival between LifeBelt CPR and manual CPR.