Testing Equivalencies of Revised Strain Index Scores: A Pilot Study

Testing Equivalencies of Revised Strain Index Scores: A Pilot Study The Revised Strain Index (RSI) is a distal upper extremity (DUE) physical exposure (PE) assessment model based on the parameters of: intensity of exertion, frequency of exertion, duration per exertion, hand/wrist posture and duration of task per day. The RSI model yields a score which is designed to be proportional to DUE PE. The objective of the study was to determine if subjects perceived similar levels of DUE PE when differing RSI parameters yielded similar RSI scores. Three subjects participated in this pilot study. Subjects performed isotonic griping tasks in three groups, each with similar RSI scores: Low RSI scores (3.0 to 3.4), medium RSI scores (10.5 to 12.0), and high RSI scores. (30.0 to 34.3). Within each RSI score group there were four tasks and each task had varied levels of intensity of exertion (% of maximum voluntary contraction), frequency of exertion (efforts per minute), and duration per exertion (seconds of exertion). Subjects performed trials in random order and were provided 2 minutes of rest between trials to prevent undue fatigue. Following each trial, subjects rated their perceived level of PE using the Borg CR-10 scale. RSI scores and Borg CR-10 ratings were correlated (R-square = 0.81). ANOVA analyses showed that Borg CR-10 scores differed between RSI categories (low vs. medium vs. high) (p\u3c0.05), but not within RSI category (p\u3e0.05). These results suggest that comparable RSI scores reflect comparable levels of PE and that increasing RSI scores reflect increasing levels of PE. This study produced statistically significant results despite its small sample size, but nevertheless further studies with larger sample sizes are warranted to determine if these preliminary results are repeatable and generalizable to larger group