Running on uneven ground: leg adjustment to vertical steps and self-stability

摘要: Human running is characterized by comparably simple whole-body dynamics. These dynamics can be modelled with a point mass bouncing on spring leg. Theoretical studies using such spring-mass models predict that self-stable. In simulations, this self-stability allows for uneven ground without paying attention to the irregularities. Whether humans actually use property of mechanical system in an irregular environment is, however, unclear. One way approach question study how leg stiffness stance and orientation flight are changed response perturbations. Here, 11 human subjects we studied two consecutive contacts during force plate adjustable height (step +5, +10 +15 cm). We found runners adjust their vertical step. The adjustment 9% increase preparation perturbation systematic decrease proportion step height. At highest (+15 cm), was reduced about 26%. also observed angle attack decreased from 68 deg. 62 increasing adjustments accordance predictions stable system. Furthermore, could describe identified forces compressions simulation given body mass, stiffness, initial conditions. compared experimental findings self-stabilizing properties model, discuss combination strategies include purely self-stabilization active neuromuscular control. Finally, beyond self-stability, suggest control may apply smooth centre kinematics.