Number of Lifts
Out of all five units, the Gorbel G-Force was associated with the largest number of lifts within the ten-minute work period. On average, the G-Force was 35% more productive than the other units (range: 12-58%).
During the precision placement exercise, actual energy expenditure was measured for each device. All five devices put up stats very closely to one another. Average energy expenditure ranged between 2.38 and 2.88 METS for each of the five units.
After normalizing the number of lifts and the actual energy expended, the G-Force showed a 52% mean improvement in productivity vs. the other four lifting devices (range 31-76%).
Comparison to Manual Lifting
After the participants used the lifting devices to complete the precision task, they were asked to perform the same precision placement task via manual lifting.
Due to the physical demand of lifting the 45 lb. weights, none of the subjects were able to complete the ten-minute work exercise without exceeding the safe heart rate zone (80% of theoretical maximum). Three of the subjects were only able to perform the activity for five minutes. One of the participants was unable to perform any of the lifts.
The figure below shows the mean energy expenditure for each option, including manual lifting. Manual lifting called for 56.3% more energy, on average, than was exerted using the various devices (range: 41.4%-70.8%).