 Traditionally, rehabilitation is initiated when loss of function is already established. Emerging evidence suggests, however, that it can be of benefit to the patient to initiate an early rehabilitation process prehabilitation starting before initiation of treatment and during treatment. Prehabilitation aims to enhance pre-treatment functional capacity for better tolerance of treatment, facilitate general recovery, and prevent development of functional impairment or reduce the extent of these problems in a long-term perspective. HNC patients have a unique set of functional challenges such as pre- and post-treatment dysphagia, pain, and weight loss and often also high baseline levels of alcohol and tobacco consumption. In addition, studies have shown that only 31 and 9 of HNC patients are meeting public health guidelines for physical activity before and after diagnosis, respectively, and that weight loss in HNC patients treated with chemoradiation begin after only 1 week of therapy. Most of the weight loss was lean body mass LBM rather than fat loss. Loss of LBM is significantly associated with physical performance and increased functional dependence. The level of physical activity typically decreases significantly during treatment. 