jointpower

Jointpower is a term used to describe the instantaneous mechanical power at a joint, a concept common in biomechanics, robotics, and related fields. It is defined as the product of the joint moment (torque) M and the joint angular velocity ω: P_joint = M × ω. The unit is the watt. The sign of jointpower follows a standard convention: positive power indicates the joint contributes work to motion (muscle or actuator generating motion), while negative power indicates energy is being absorbed at the joint (eccentric action or damping).

In biomechanics, jointpower helps quantify how energy is transferred through joints during movements such as walking or running. It is typically estimated from motion capture data and ground reaction forces to obtain joint moments, combined with angular velocity from kinematics. Positive and negative phases reveal propulsion versus energy absorption, aiding assessments of efficiency, performance, and injury risk.

In robotics and prosthetics, jointpower relates to the power requirements of actuators at a joint. It informs control strategies, energy budgeting, and efficiency optimization for dynamic tasks. Instantaneous jointpower can be used in real time to regulate torque delivery, fatigue modeling, and energy recovery schemes.

Measurement and interpretation often involve computing net jointpower over a task by integrating P_joint over time. Examples include knee power during sprinting, hip power during stair ascent, or elbow power in a robotic arm. Related concepts include joint torque, angular velocity, and positive versus negative work, with jointpower serving as a concise metric of energetic exchange at a joint.