Addressing traditional and environmental risk factors can keep workers injury free.Rehab providers in industrial medicine often operate in a gray area. It can be difficult to connect a specific workplace injury to a single job task, posture, lifestyle behavior or hereditary trait. Many elements may be at work.But employers are becoming more aware of the causative relationship between modifiable risk factors and cumulative trauma disorders (CTDs) at work. While the mere presence of a risk factor doesn’t necessarily relate to injury risk, it may cause, aggravate or precipitate a CTD.In fact, according to research from the National Safety Council, it’s possible that interacting risk factors have a multiplicative effect, which can significantly increase the likelihood of microtrauma and worker injury.Ergonomic and industrial medicine professionals can play a role to reduce the number, frequency and effect of workplace hazards. Doing so requires an understanding of the difference between traditional and non-traditional (environmental) risk factors, and recognizing the steps to reduce their consequences.TRADITIONAL RISK FACTORSWhen lowering the risk of cumulative trauma disorders, your main consideration is sufficient blood flow. Maintaining an adequate supply of oxygen-enriched blood to working tissues ensures metabolic efficiency, and minimizes the adverse effects of tissue overload, fatigue and microtrauma.The key to adequate blood flow lies in the balance between work and human physiology. Attempt to mitigate the following contributors to cumulative trauma and fatigue.Task repetition.Most work tasks involve repetition of some degree, but high task repetition is a common risk factor for CTD. High task repetition can also magnify the effects of other risk factors. Control methods are important.A job task is highly repetitive if the cycle time is equal to or less than 30 seconds, or if more than 50 percent of the time involves performing the same fundamental cycle. Because most work cycles are determined by daily production quotas or machine pace, workers can’t always control their pace or work-rest cycle.However, a job rotation program can reduce overall exposure, and mechanical aids can reduce contraction force and duration. Adjust machine pace and production quotas, and stress the importance of rest and stretch breaks.Forceful exertions.Force exertions are the manual efforts required to accomplish a specific task, movement or action. The higher the magnitude of force, the higher the fatigue risk.To control microtrauma from forceful exertions, recommend mechanical aids or power tools, mechanical lifting devices, counter balance systems, transport carts and dollies. Instruct workers to slide objects rather than carry them, and use conveyor systems for long distances. Eliminate physical barriers, reduce the weight’s lever arm, cut down the size and shape of raw and produced materials, and use adjustable height or lift tables.Proper work area and tool design principlesprovide appropriate object handling, efficient work interface design and good work flow. Implement rest or stretch breaks for tissue recovery and better circulation.Static muscle contractions.Static muscle contractions, such as holding an object for inspection, can fatigue workers at much faster rates than intermittent contractions. Higher utilization of nutrients, oxygen and energy within the working muscle lowers metabolic efficiency, inhibits blood flow, raises internal pressures and facilitates anaerobic metabolism and local muscle fatigue.To control its effects, limit high-effort static contractions to less than 10 seconds, moderate effort contractions to less than 60 seconds, and light effort contractions to less than 4 minutes. Provide alternatives to grasping objects for extended times. Implement mechanical aids, job rotation and rest or stretch breaks.Posture.Awkward positions overload muscles and tendons, and load joints asymmetrically, increasing joint compressive forces. Workers should avoid long periods of stressful positioning, and vary postures and rotate jobs. Evaluate and modify a worker’s area to maintain joint range of motion in the neutral or mid-range positions, d esign tools that maintain neutral joint postures, and stress the need for rest and stretching.Contact stress.Continuous use of tools, or leaning on work surfaces with hard or sharp edges, can compress and impede blood flow and nerve conduction. In addition, weight bearing on the wrist and pounding with the hand can diminish blood flow and nerve conduction in soft tissue.
Help control the microtrauma from these motions by providing tools for pounding and hammering. Better equipment and tool design ensures appropriate handle sizes and shapes. Modify sharp edges by rounding or adding padded covers, and use power or spring-loaded tools to reduce contact pressure and promote blood flow.