Exploring biomechanical and metabolic determinants of lifting movement strategy

We explored if lifters would adopt a spine sparing strategy when lifting heavier loads infrequently, and a metabolically cost-efficient strategy when lifting lighter loads more frequently. Twenty-six participants performed four 7-min bouts of lifting in high-load low-frequency and low-load high-frequency conditions. Participants chose self-selected lifting strategies for bouts 1 and 4 in each condition but were required to complete lifts using a stoop and squat for bouts 2 and 3 to sample a biomechanical and metabolic costs landscape. Whole-body kinematics, ground reaction forces, and oxygen consumption were collected to quantify peak sagittal low back moments, V˙ O₂ consumption, and lifting strategy. No significant differences were found in biomechanical and metabolic cost exposure variables between the first and last self-selected lifting bouts after an exploration period of a cost landscape. However, participants did adopt different movement strategies between conditions, biased toward a more metabolically cost-efficient stoop-like lift in the low-load high-frequency condition. This evidence indicates that metabolic cost likely plays a task specific role in shaping lifting strategy, an important finding for researchers developing digital human models aiming to predict how people might lift at work.