Inclusion Criteria:  Chinese adults who are aged 18 years to 64 years and are diagnosed with mild or moderate ID based on the information provided by the residential care facilities; Able to understand basic information and instructions of the intervention and to make decisions upon their participation; Classified as physically inactive (i.e., <150-min moderate-intensity or 75-min vigorous-intensity PA/week); Currently using residential service user as stated in the Social Welfare Department of Hong Kong SAR.  Exclusion Criteria:  Currently enrolled in a regular exercise program; Physically unable to participate in the MVgPA, such as having significant mobility problem; Participation to MVgPA will put them at physiological risk; or At risk of self-harm as determined by the staff of the residential care facilities.