... fromheel-strikemotion.Somedevicesusetheenergyfrom the relative motion between the foot and the groundduring the stance phase (the phase in which the foot ison the ground). Others use the energy from the bendingof the shoe ... 1) the ener gy spent to generate the electrical power, and 2)theenergyspentbytheuserincarryingthedevice,which is a function of the device weight and the locationof the device on the body. Therefore, ... while the human angular velocity fora typical joint is of the order of 20 rpm. Yet, the higher the gear ratio, the greater the losses due to friction, andthehighertheweightofthedevice.Theseconsidera-tions,...