Apparatus for exercising the neck includes a head assembly connected to an anchor assembly by a flexible tether that has a resilient elastic portion. The head assembly includes a cap portion, an adjustable harness to secure the cap portion on the head and a saddle piece that extends across the back of the neck along the atlanto occipital joint when mounted. The cap portion can be a rigid helmet that forms a cam surface with a channel for slideably receiving the tether and may include a frontal extension forming a continuation of the cam surface. The tether is secured to the posterior of the helmet so as to extend over the cam surface to the anterior portion. The method includes engaging the atlanto occipital joint region with a saddle coupled to a source of variable force and extending the head and neck into an extension orientation against the force.