Cardiovascular Disease (CVD) is a leading health problem in Australia, USA and other western countries. The management of CVD, following a cardiac event, is managed through cardiac rehabilitation (CR) programs over 4 to 12 weeks, which also prescribes a daily recommendation of at least 30 minutes of moderate physical activity, as outlined by most national bodies of CVD guidelines. Currently, there is no way of measuring physical activity other than through self-reporting or diary or 6 minute walk test (6MWT) at the hospital exercise clinics. Following a validation study of metabolic expenditure (MET) derived from accelerometer-based ambulatory monitors with the traditional measure of MET from oxygen consumption (VO2) output from a breath gas analyzer (Cosmed srl, Italy), resulting in a highly linear correlation (r2=0.88), it was tested on 23 patients undergoing a 6-week CR program at 2 Queensland hospitals. The patients wore the accelerometer device continuously at home and during exercise sessions at the hospital. Different stages (PRE, END, and EXIT) of CR program of patient progress were assessed using 6MWT and compared with ambulatory MET values. Increases in patients' free living MET values from PRE, to END and EXIT stages significantly correlated with that of 6MWT measures at the exercise clinic (r2=0.72, p<0.01). Ambulatory assessment of MET through accelerometers can be used as surrogates of clinical 6MWT to measure physical activity for CR programs in home-based care.