Mechanical and metabolic consequences of sagittal trunk lean angle in walking – A dynamic walking perspective

Bipedal walking requires a balance of muscle work and energy losses, with models indicating that powering gait with ankle push-off is more energetically economical than powering with hip joint work. This study investigates how varying trunk lean angle affects joint mechanics and energy expenditure during walking. We hypothesized that leaning forward would increase hip work, reduce ankle push-off, and increase energy consumption, and leaning backward would have complementary effects. Healthy young adults walked at 1.3 m/s while adjusting their trunk angles from backward 15° to forward 60° using visual feedback from a chest-mounted inertial motion sensor. Center of mass mechanics and lower-body joint mechanics were estimated using motion capture and force treadmill measurements, alongside metabolic rate using respirometry. With forward trunk lean, center of mass (COM) work became more negative during collisions, increased in the middle of stance phase, and was reduced in push-off. At the joint level, forward trunk lean led to increasing stance-phase hip moment and hip work, while ankle work decreased for moderate trunk angles. The early vertical ground reaction force peak and loading rate also increased with forward trunk lean. Backward trunk lean led to reduced hip work, increased ankle work, and increased push-off work. Metabolic rate was minimized in the 0° condition and increased with trunk lean in either direction. Trunk lean significantly impacts lower-limb mechanics and energy consumption, with a trade-off between hip and ankle work, suggesting potential applications for improving walking in populations with diminished push-off, such as older adults.

This dataset contains data from n=10 healthy young adults. They walked with trunk lean angles of backwards 15 degrees, neutral, and forward 15, 30, 45, 60 degrees. Here we included the *.c3d motion capture files, an excel file explaining what all the conditions were named, the *.cmz visual 3D workspace for each of the 10 subjects, the Excel files of the metabolic data for all of the subjects, a summary Excel file of the metabolic rates for all the subjects, a MATLAB *.mat file containing the dimensionless and dimensioned results after processing (including both the averages for each condition and a matrix of the averages of each condition by subject), and MATLAB code used to process the results.

Methods
Human subjects (healthy young adults) walked on a treadmill at 1.3 m/s with their trunk inclined to different controlled sagittal angles (-15, 0, 15, 30, 45, 60 degrees forward of their customary walking posture). We measured oxygen consumption, motion capture, and ground reaction forces, and computed energy expenditure and biomechanical outcomes to determine the relationship between hip and ankle work across conditions and other accompanying biomechanical phenomena. For further details refer to the methods in the associated paper.