The aim of this population based study is to examine, quantify and describe physical activity level in Norwegian boys with DMD, and to compare the level of physical activity level between boys with DMD and age matched healthy boys. A co-project will validate ActiGraph accelerometry to measure physical activity in boys with DMD.

International guidelines recommend regular physical activity for boys with DMD, and participation in physical activity plays a key role in the management. Paradoxically, patients with severe neuromuscular disease like DMD, have considerable limitations to participate in such activities. Limitation may be muscle weakness, pain, fatigue, reduced mobility and overall function, and also limited knowledge of physical activity benefits among health care personnel. Limited participation leads to a sedentary lifestyle, and gradual under-use of still functioning muscles may cause secondary deterioration in DMD.

The current physical activity level amongst Norwegian DMD's are unknown, and physical activity registration and self-reported questionnaire will be examined in this study.

Inclusion Criteria:

• Boys with conclusive diagnosis of Duchenne Muscular disease, attending Norwegian pediatric rehabilitation clinics.
• Signed written consent
• Able to answer questionnaires with help from parents, care giver(s) or health care professional with regular follow up of the participants.

Exclusion Criteria:

• Lack of consent.
• Language difficulties
• Cognitive dysfunction or mental retardation leading to difficulties in answering the questionnaires adequately

DMD is X-linked disease

Study population will be requited from all the Norwegian regional pediatric rehabilitation centre's out patient clinics. Verbal and written information about the study will be provided if inclution criteria to be met.