Power-Assist Wheelchair Devices - Handrim-Activated A power add-on unit is a device that converts a manual wheelchair to a powered wheelchair. There are 3 different types of power assist devices: ones that attach to the front of the manual wheelchair to assist by "pulling" the wheelchair, ones that attach at the rear of the manual wheelchair to "push" the wheelchair, and ones that attach to the hub of the rear wheels to assist by multiplying the human force that is applied to the handrim. This last type generically is known as a handrim-activated power assist drive system and is the subject of this months Clinical Corner. 2022-03-01 Keep Reading