Methods, systems, and apparatus for powering and/or recharging medical devices implanted within the body are described. An illustrative implantable medical device includes a housing having an internal cavity and a flexible anchor assembly that is coupled to the housing. The flexible anchor assembly includes a first electrical conductor, a second electrical conductor, and a piezoelectric layer that is disposed between the first and second electrical conductors and that is configured to displace in response to a physiologic force applied to the flexible anchor assembly and generate a voltage differential between the first and second electrical conductors. The implantable medical device includes power circuitry that converts the voltage differential between the first and second electrical conductors into an operating current for powering one or more components within the implantable medical device and/or for recharging a rechargeable power supply within the device.