The Chair Exerciser is an apparatus and method to exercise one's core, back, and legs while working on tasks that are normally performed seated. These tasks include computer work, watching television, or computer gaming. The Chair Exerciser fits on a regular chair and one sits upon it. The Chair Exerciser's resistance can be adjusted to the suit the needs of the user. The multitasking of work and exercise is an attractive benefit to the Chair Exerciser. The Chair Exerciser can also be formed as an integral part of the chair as opposed to a portable unit.