Strain Index Methodology

The strain index methodology was developed to provide an easy way to assess ergonomics associated with the tasks of a particular job for the person performing the work. The stain index methodology for job evaluation results in a numerical value. This value is called the SI score. The SI score is associated with the risk of developing distal upper extremities disorders. The strain index requires the measurement or estimation of six different task variables. These variables are: intensity of exertion, duration of exertion per cycle, efforts per minute, wrist posture, speed of exertion, and duration of task per day. Intensity of exertion is described as an estimate of the force requirements to perform a task. It reflects the magnitude

The lowest rating of one is classified as less than ten percent of the time of the task the maximum level of exertion is performed. A 2 rating is described as ten to twenty-nine percent of the time the maximum level of exertion is performed. The rating of three means that thirty to forty-nine percent of the time the maximum level of exertion is performed. The four rating is classified as fifty to seventy-nine percent of the time the maximum level of exertion for the worker is performed. If the maximum level of exertion is greater than eighty percent of the time the duration of the exertion is given the five rating. The multipliers for the duration of exertion are given in such a manner as the longer the time the task is performed the higher the affect it has on the SI index. The rating of one receives the multiplier of .5. The rating of 2 receives a multiplier of one. The rating of three gets the multiplier of 1.5. the rating of four assigns a multiplier of 2. The highest rating of five is given the multiplier of 3. Efforts per minute is the third item that needs to be estimated. Another way to look at the efforts per minute is to analyze how many time per minute the task is performed. The efforts per minute could also be labeled as