Improved assemblies, systems, and methods provide an implantable pulse generator for prosthetic or therapeutic stimulation of muscles, nerves, or central nervous system tissue, or any combination. The implantable pulse generator is sized and configured to be implanted subcutaneous a tissue region. The implantable pulse generator includes an electrically conductive case of a laser welded titanium material. Control circuitry is located within the case, the control circuitry including a rechargeable power source, a receive coil for receiving an RF magnetic field to recharge the power source, and a microcontroller for control of the implantable pulse generator. Improved assemblies, systems, and methods also provide a stimulation system for prosthetic or therapeutic stimulation of muscles, nerves, or central nervous system tissue, or any combination. The stimulation system provides at least one electrically conductive surface, a lead connected to the electrically conductive surface, and an implantable pulse generator electrically connected to the lead.