Temporal relationship between trunk and thigh contributes to balance control in load carriage walking

Load carriage walking (LCW) challenges a person's balance as the load increases their forward trunk inclination, shifting the center of mass (COM) forward with respect to the base of support (BOS). We examined LCW to understand whether and how healthy people adjust the temporal relationship (TR) between the trunk and leg for balance control. Ten subjects were recruited to perform unloaded walking and LCW. The TR between the trunk and leg was measured by the continuous relative phase. The maximum forward displacement of the COM with respective to the BOS (FDCOM(BOS)) was recorded during the stance phase. We found that the TR was shifted in LCW, and the shift was associated with a decrease in the maximum FDCOM(BOS). The findings suggest that the TR between the trunk and leg contributes to balance control, and it may be a variable that needs to be addressed in gait rehabilitation.