Estimated energy expenditure during a manual material handling task: the prolonged effect of wearing the Oxylog System

Abstract

This purpose of this study was to evaluate the prolonged effect of wearing the Oxylog System from Morgan Scientific, Inc. during a series of four manual material handling tests. The lift tests were performed by 12 males (average age of 23 years); each participant completed a 15-minute submaximal step test and a series of four lifting tests at two different lift rates (8 and 16 lifts/min) for an hour duration each. The lift test protocol used in this study was designed to accurately simulate a repetitive manual material handling task commonly found in industry settings. Lift rates were selected to resemble the work rates commonly observed in material handling environments. Heart rate was directly measured during all four tests; for two tests, the Oxylog system was worn to directly measure the working V. 02; the resulting heart rate data was compared to the heart rates resulting when the participant wore only the heart watch. For this test design, V. O2 values were estimated using linear regression from the submaximal step test results. The averages of the participants' heart rates were consistently higher during the tests while wearing the Oxylog for both lift rates. Analysis of variance (ANOVA) results for working heart rate found that there was a difference between the average heart rate values for 16 lifts/min (p = 0.0 1 6); however, at 8 lifts/min, the difference was not significant (p = 0. 109). Statistical analysis comparing estimated versus measured working V. 02 indicates that there was no difference between V. 02 while the Oxylog was worn compared to when it was not worn for both lift rates (p = 0. 1081 for 8 lifts/min; p 0.2408 at 16 lifts/min). Furthermore, negative physical and psychological effects associated with wearing the Oxylog were reported. Participants expressed an increase in difficulty when lifting and lowering while wearing the Oxylog, particularly at the faster lift rate. Energy expenditure during the task was compared to Garg's metabolic energy expenditure prediction equations. Average percent difference between value predicted by Garg and measured by the Oxylog was a positive 67% for 8 lifts/min and a positive 9' )% for 16 lifts/min and was statistically significant (p=0.000 1).