In this study, eight healthy male adults ages 20 to 35 lifted a heavy crate from the floor to waist height. Each man lifted the box three times using a different lifting method.
Freestyle, stoop, and squat methods were used in differing orders by each man. The crate was lifted holding it in five different distances away from the body. Each man lifted the crate a total of 150 times.
A special motion analysis system was used to record spine motion. Special markers were placed on the spine, pelvis, hip, and knee. Two cameras took photos of the spine position throughout each lift. Computer software used the data to calculate angles of the spine during the various types of lifts.
The researchers were looking for the effect of lift style and lift distance on the spine. Two areas of the spine involved were the thoracic and lumbar regions. The authors report the following findings:
The results of this study suggest that even when we stoop to lift a heavy item, the spine still flexes the same amount. The ligaments and joint capsules are probably under the same amount of stress and strain no matter which method is used. Likewise, compression and shear forces in the lower lumbar spine are the same when lifting with each style and distance from the body.
The authors conclude that the risk of low back injury is the same no matter what lift style is used. These findings support similar results from other studies on this same topic.