Frequent heavy lifting can be a major contributing factor in lower back pain (LBP), but researchers disagree when it comes to the most effective lifting mechanism to reduce spinal loads and avoid injury. While the adage, “Lift from the legs, not from the back,” sounds like good advice, recent study findings 1 suggest the benefits of “squat” lifting over “stoop” lifting may have more to do with how the load is positioned than which muscles are engaged in picking it up. The results of the in vivo study indicate a need for further research on the topic, as LBP caused by heavy lifting is responsible for missed work and high disability rates—especially in the male population. Understanding the biochemical processes involved in the different lifting techniques and how to best position loads in preparation for lifting could help alleviate injuries that cause pain and represent a tremendous cost to society.
While numerous previous studies have compared stoop lifting (using the back, keeping knees straight) and squat lifting (bending the knees, keeping the back straight), with conflicting results, this study utilized a telemeterized vertebral body replacement (VBR) to acquire in vivo measurements of lumbar spinal compression and implant forces during different spinal loading scenarios, with several study subjects. The purpose of the study was to determine if the initial weight location of a load had a significant bearing upon the amount of lumbar compression and if lifting a weight from the side with one hand would result in a lighter implant force than lifting the same load from the front.
Four male patients with compression fractures of the lumbar vertebral body were informed prior to the study that they would receive modified VBRs. Three of the subjects received the VBR in the first lumbar vertebra (L1), and one of the subjects received his VBR in the third lumbar vertebra (L3). Over the course of two surgeries, their fractures were stabilized with a fixation device which, along with the fractured vertebral body and adjacent discs, was subsequently removed. The VBR devices were then implanted and bone material was used to assist in the fusion process.
The patients were instructed on the proper mechanics of both lifting techniques (stoop and squat) and were measured over the course of 17 sessions as they employed the two techniques a total of 104 times. The patients lifted a crate with two hands from a position in front of the body, and they lifted the identical crate from a lateral position, using one hand. The crate location measurements were compared over nine sessions. The data collected identified the resultant force – the sum of three measured force components—as the determinant mode acting upon the VBR during the experiments, in which stoop—and squat-lifting were performed equal or near-equal amounts of time.
The results of the study suggest that lifting from the side with a single hand results in slightly less (14%) VBR force than lifting from the front, but there is no significant difference (4%) between stoop and squat lifting in the effects of spinal loading. The study’s authors point out that there was significant variance in each patient’s lifting execution, fitness level, coordination, and flexibility, and this and other differences in loading techniques might have influenced the study’s findings. Since load-lifting efficacy may be dependent on different spinal sections (lower or upper lumbar), the study’s authors point to the need for a broader and more detailed study to determine with more certainty the effects of various load-lifting techniques on the lumbar spine’s biochemical and structural forces. Nevertheless, results of the study suggest that lateral, single-handed lifting and –more significantly—reducing a weight’s distance in anterior-posterior lifting may help reduce the effects of spinal loading.