New Assessment Tools and Interventions to Manage MSD Risk


Wednesday, May 25, 2016, 10:00 AM - 12:00 PM


The ROI of Onsite Early Intervention to Prevent Strains and Sprains

T. Silva, Atlas Injury Prevention Solutions, Grand Haven, MI

Situation/Problem: Many organizations invest significant time and money into ergonomics programs and equipment, But they still fail to reach zero recordable incidents due to a variety of factors, which often include: aging, unhealthy, or overweight workforce, engineering controls impossible to implement, and employees seeking medical treatment without attempting conservative care.

Resolution: This presentation will look at a case study for a tier 1 auto parts manufacturer and how they implemented an on-site early intervention and ergonomics program to reduce their recordable incidents. It will show how the early intervention and ergonomics process was implemented using the Plan-Do-Check-Act model. It will also show how the flow of information in its injury management activities has been pushed upstream to manufacturing and product design engineers to address the root causes of ergonomics hazards in the facilities.

Results: Significant reductions in recordable incidents. Greater employee engagement. Identification of root causes in product and process design so that corrective actions can be taken to solve the problems. The full integration of data used by safety, ergonomics, HR, workers’ compensation, and case management professionals.

Lessons learned: Learn the process for effectively launching and providing value-added on-site support using the Kaizen methodology. Discuss the keys to early intervention and how to prevent an OSHA recordable, including injury triage to determine if the concern can be managed conservatively or if further evaluation and assessment is warranted. Discuss how a comprehensive inventory of Job Demands Analyses can be used as the basis for further preventing recordable incidents through: Post-offer pre-employment screens; Ergonomics risk assessments; and Return to work job matching.



Ergonomics & the Aging Workforce: What's New with the Aging Population?

B. McGowan, Humantech, Inc., Ann Arbor, MI

Situation/Problem: In 2009, older workers (55 and over) represented 19% of the U.S. workforce. This group is the nation's fastest growing segment of the workforce. The Bureau of Labor Statistic (BLS) projects, for the period between 2006 and 2016, that there will be an 84.3% increase in workers age 75 and over, an 83.4% increase in workers between the ages of 65 and 74, and a 36.5% increase in workers between ages of 55 and 64. Many industrial job duties require physical demands such as lifting, lowering, pushing, pulling, bending, twisting, reaching, climbing, and kneeling, among others. Each of these job demands require forceful, repetitive, or sustained muscle contractions. For the younger worker, the physical capabilities for job duties are well defined and have resulted in the publication of several design standards. Unfortunately, the physical capabilities of the older worker have not been studied as extensively, and as a result, design standards for older workers are hard to find. The purpose of this presentation is summarize the latest physiology research and the cutting-edge ergonomic design guidelines for the aging workforce.

Resolution: Research was conducted to find citations related to changes in muscle physiology as we age. The aging population is considered 55 years of age or older. Topics of interest included changes to sensory/motor perception and control, strength, movement control, and cardiovascular capacity.

Results: The review of literature found several new changes in muscle physiology as we age. There is a loss of muscle mass and strength that occurs starting at 40 years old and continues with increasing age. Alterations in muscle fiber transitions and metabolic shifts impact the aging muscle. Key performance changes that occur as a result of the changes in muscle physiology as we age include: 1) movement speed slows during grasping and reaching; 2) movement precision (deceleration) decreases; 3) range of motion is reduced; 4) muscle strength (grip, push, pull) decreases; 5) force control decreases, as adults grip twice as hard to compensate; 6) force perception decreases; and 7) muscle endurance decreases. Based on these findings, cutting-edge ergonomic design guidelines for lifting, lowering, pushing, pulling, bending, twisting, reaching, climbing, and kneeling were developed for the aging workforce.

Lessons learned: The changes in muscle physiology as we age are real, and impact workers’ capabilities to perform work. Understanding the capabilities of the older worker allowed for the development of design standards to optimize performance and to minimize musculoskeletal disorders for the aging workforce.



Development of a New Assessment Tool for Musculoskeletal Disorders Associated with Lifting and Bending

R. Phalen, University of Houston Clear Lake, Houston, TX

Objective: Back injuries associated with forceful and repetitive lifting or bending activities are a major source of work-related disability, especially among those working in the transportation, warehousing and healthcare sectors. It is estimated that the economic impact of low-back disorders is as much as $50 billion dollars per year in the United States alone. Unfortunately, over the past decade, we have not seen much improvement in the incidence or severity of these disabling disorders. One critical barrier is the lack of effective assessment tools to evaluate and control known stressors, such as load weight, load position, human posture, frequency and duration of exposure, and dynamic motion (acceleration). Current techniques are either: 1) complex and cumbersome devices or 2) simplistic models, which often fail to take into account one or more critical stressors. The aim of this current research is to develop a new assessment tool that can be worn by a worker and assess the forces and moments (torque) on the lower lumbar region of the spine.

Methods: Small force plates were positioned under major load bearing regions of the feet, namely at the heel and ball of the foot, to measure lower-trunk weight distribution. Based on the position of the feet relative to the pelvis and lower lumbar region o​​​f the spine, an algorithm was used to approximate the magnitude and direction of force at the lower lumbar region. Triplicate readings were collected for various lifting, bending and twisting motions. The results were then compared to matched results for a common biomechanical model (HAT) and the revised NIOSH Lifting Equation.

Results: It was determined that lower trunk weight distribution can be used to approximate the moment (Nm) on the lower lumbar region. The resulting vector magnitude (N) was correlated with the corresponding HAT moment estimate (Pearson r = 0.8026; p ≤ 0.05). The results were also correlated with the corresponding NIOSH multipliers for vertical distance, horizontal distance, and asymmetric angle (Pearson r = 0.7682; p ≤ 0.05). In addition, the lower trunk weight distribution method successfully measured increases in force magnitude associated with dynamic motion.

Conclusions: Lower trunk weight distribution can be used to approximate and evaluate forces on the lower lumbar region. The results were comparable with existing assessment tools. Additionally, this new method can also be used to evaluate dynamic motion effects, associated with picking up or setting down a load.



The Influence of Loading Parameters on Fatigue Life of MSD Tissues

S. Gallagher and M. Schall, Auburn University, Auburn, AL

Objective: Several lines of evidence have recently emerged to suggest that a fatigue failure process may be associated with the development of MSDs and may be a causal mechanism in their progression. These lines of evidence include in vitro testing of musculoskeletal tissues, results from animal models, data from epidemiological studies, and studies of eccentric exercise in humans. If true, there are numerous implications regarding MSD risk assessment. The objective of this presentation is to describe the influence of loading parameters on fatigue life of musculoskeletal tissues.

Methods: Data from in vitro materials testing of a rabbit medial collateral ligament (from Thornton et al. 2007) was used to develop estimates of tendon fatigue life given varying duty cycles using the Gerber criterion. Data indicate that the ultimate stress of the ligament was 100 MPa and the fatigue strength fraction determined to be 0.42, and the endurance limit assumed to be 30 MPa. Using these data, estimates were developed for a 40 MPa load at various duty cycles (40% versus 70%).

Results: The mean stress for a 40% duty cycle was determined to be 13.93 MPa while the 70% duty cycle had a mean stress of 25.87 MPa. Based on the Gerber criterion, calculations of the fatigue life for these duty cycles were 19300 and 12147, respectively.

Conclusions: Various parameters related to loading of musculoskeletal tissues will be important with respect to the number of cycles that can be experienced before damage occurs. In this analysis, the influence of duty cycles demonstrated a significant influence on fatigue life with the 70% duty cycle demonstrating a more than one-third reduction in the fatigue life compared to the 40% duty cycle. All other things being equal, reducing the duty cycle would be expected to reduce the risk of experiencing musculoskeletal disorders.



Prevalence of Musculoskeletal Discomfort Related to Standing Works—Results from a Multi-Organization Study

Y. Huang, National Kaohsiung First University of Science and Technology, Kaohsiung, Taiwan

Objective: Musculoskeletal discomfort is a widespread problem affecting labor intensive and office based workers alike. Causal relations with musculoskeletal discomforts on the upper limbs and lower back have been examined extensively. In contrast, relatively little has been examined as to the extent and severity of musculoskeletal discomfort due to prolonged standing. Besides occupational and work-related factors, personal characteristics may also affect the occurrence and severity of symptoms. The occurrence of musculoskeletal discomfort related to standing work and potential risk factors were examined in this study.

Methods: A personal questionnaire was designed for this study. Various organizations were contacted for study participation, and most of the employees at the time of site visit were invited for participation. Questionnaire items included personal characteristics (age, gender, height, body weight), work history, work conditions (including break arrangement, rest area arrangement). Finally, the study participants were asked to point out locations and symptoms of musculoskeletal discomforts at the end of a typical work day. Statistical analyses were performed with the questionnaire data to determine how personal characteristics and work factors may be related to musculoskeletal discomforts.

Results: In all, 1,585 personal questionnaires were collected. Most (72.7%) of the study participants were women, and over 80% of the study participants work at least 20% standing during a workday. Some also had to work on their knees, bending waist, manually moving objects, or walked a lot during the day. Before the end of a workday, 81.6% reported at least one general discomfort symptom, and 70.3% reported musculoskeletal discomfort. Compared to seated work, workers who spend some of the workday <span style="line-height: 13.8666658401489px;">on their feet.

Conclusions: Prolonged standing at work was common in this study. Although there are steps to help reduce health hazards associated with prolonged standing, they have not been widely recognized or implemented in the workplace. Further studies are needed to evaluate possible cause of these discomfort and to find remediation to these occupational hazard.



Do Sit-Stand Workstations Warrant the Attention They Are Receiving?

D. Hunt, Carleton University, Ottawa, ON, Canada

Situation/Problem: Sit-stand workstations have been on the market since the 1990’s when the sit-stand office paradigm was proposed. Recently, we have seen a sharp rise in their popularity. It is believed that their increased demand has been related to evidence associating prolonged sitting with chronic disease and mortality. Given the increase requests from workers for these types of units, the desire for sit-stand workstations to become considered standard office furniture is possible. That type of inclusive, overarching philosophy can have serious investment (cost and time) implications.

Resolution: A review of the current scientific literature surrounding sit-stand devices was completed. To date, studies have focused on a wide range for outcome measures, such as: worker discomfort, health benefits, productivity, alertness, and worker perception. As an Industrial Hygienist, the increase in demand from workers makes it important to understand the effectiveness of these devices and how they play into managing musculoskeletal disorders (MSD) risk. The following issues will be addressed: 1) What are the main driving forces behind the recent demand for sit-stand workstations? 2) Are the reported benefits of sit-stand workstations supported by scientific literature? and 3) Are there any research supported sit-stand set up guidelines?

Results: Installing sit stand workstations as a means to encourage decreased sitting time and encourage health based outcomes are increasing in merit. Literature is also supporting the idea that sit-stand workstations may be beneficial in increasing worker comfort and decreasing MSD risk. Lastly, there are implementation details that should be considered in order to increase the success of a sitting reduction program.

Lessons learned: The majority of literature surrounding sit-stand workstations is favorable as it relates to reported worker discomfort, productivity and perceived value. Additional studies evaluating MSD specific outcome measures and long term compliance would be beneficial. In closing, sit-stand workstations may be helpful in providing postural changes for office workers. However, this option for encouraging movement at work is not the only tool available. As a result, caution is needed to ensure this solution is balanced with the realized MSD risk reduction obtained when installing these devices and the level of investment required at an institutional level to ensure success.​