Management of body energy and frontal plane angular momentum during unpredictable and adapted drop-like gait perturbations

Mechanisms that manage total centre of mass (CoM) energy and frontal plane whole-body angular momentum during unpredictable without experience and predictable with experience drop-like gait perturbations were investigated in 18 participants. Electromyographic activity from seven bilateral lower leg muscles and whole-body kinematics were recorded. We found a significant (p < 0.05) increase in the peak-to-peak range of total CoM energy and frontal plane whole-body angular momentum during both perturbations, indicating an increased challenge in managing body stability. After the plate dropped, participants rapidly increased muscle activation of the perturbed leg to effectively manage CoM energy. The increased muscle activation was significantly associated (p < 0.001) with the rate of frontal plane whole-body angular momentum, indicating a trade-off between the mechanisms that manage total CoM energy and frontal plane angular momentum. Predictive adjustments in foot placement, joint kinematics and muscle activation patterns of both the contralateral and perturbed legs regulated mechanisms that effectively managed both total CoM energy and frontal plane angular momentum during the predictable perturbations. Finally, during the second part of the stance immediately after the perturbation, and especially during the unpredictable drop-like perturbations, trunk movement appears to be very important for controlling whole-body angular momentum in the frontal plane.