FINDING THE RELATIONSHIP BETWEEN COUPLING MULTIPLIERS SUPPLIED BY NIOSH
LIFTING EQUATION AND THE CORRESPONDING MUSCULAR ACTIVITY
By: Yi Wang
Faculty Advisor: Dr. Magdy Akladios
The objectives of the study is to investigate, whether there exists a difference in muscular activities during lifting among different population groups, whether there is a difference between the results obtained from the present study and coupling multipliers supplied by the NIOSH Lifting Equation, and whether subjects’ psychophysical subjective feedback match the results of the objective measures obtained from the experiment. Thirty healthy participants from different races with no history of low back pain or musculoskeletal issues are to be selected for the present experiment. Before and after the experiment, a survey will be distributed to the subjects to complete in order to collect all the information needed for this study. Experimental subjects are going to lift loads of 10 pounds with three coupling methods, which are “Good”, “Fair” and “Poor”, with horizontal distance = 10 inches, vertical distance =
30 inches, distance being moved ≤ 10 inches, twisting angel = 0 degree, and average frequency =
0.2lifts/min. For each lift, the surface electromyography signals from the forearm flexor and extensor, upper arm biceps, shoulder middle deltoid and anterior deltoid, upper back trapezius, middle back latissimus dorsi, and lower back erector spinae, will be recorded. The muscular activities are to be evaluated and determined by the amplitude of EMG signals from eight different muscle groups. The study will use one-way analysis of variance to determine whether the means of muscular exertion of different muscle groups during lifting are significantly different among races, and if there is significant difference, the study will further use Fisher method to determine the significantly different pairs of means at α=0.05.
After each lift, the subjects will be asked to rate the perceived exertion for different muscle groups, and this RPE, as a psychophysical subjective feedback, is used to determine whether there is a gap between the subjects’ psychophysical subjective feedback and the results of the objective measures obtained from

the experiment. As “Poor” coupling is theorized to increase lifting and grip stress, “Poor” coupling would be set as the reference value to calculate the percentage of decrease in muscle strength for “Good” and
“Fair” coupling, and the obtained values will be evaluated by comparing to the coupling multipliers supplied by the NIOSH Lifting Equation. The expected results for this study would be, there exists a difference in muscular activities during lifting among different population groups, there is a difference between the results obtained from the present study and coupling multipliers supplied by the NIOSH
Lifting Equation, and subjects’ psychophysical subjective feedback might not match the results of the objective measures obtained from this experiment.