Dementia is a global issue, and it is a growing problem. Exercise is an effective intervention strategy for improving cognition and physical function for people of all ages, and measurement is fundamental to scientific endeavour. This thesis sits at the crossroads to these three key areas. Without appropriate psychometric justification behind the choice of measurement tools for exercise intervention studies, the validity of outcomes to suggest that exercise is beneficial for people with dementia should be called into question. This thesis aims to identify common measures of physical function, a key construct to remaining independent for people with dementia, assess their psychometric properties and determine whether such significantly different in the first trial (p<0.05), generally these differences were no longer present by the third trial (p>0.05). It was evident that the majority of our sample were able to complete the measures to standardised the protocol. In Stage Four, the previous definitions of physical function, which centre on capacity to complete complex and basic daily tasks, is appropriate for people with dementia.However, further attention should be given to the tasks most basic and central to remaining independent.The discussion focussed on three main findings from this thesis. These are; there is reasonable evidence to support the use of assessed measures, intended use should guide clinicians and researchers, and simple measures for people that have low physical and low cognitive function should be used. Implications will translate these main findings into expected consequences of this work. To my friends, mentors and family who have walked along side me throughout the course of my candidature, I cannot begin to put into words the debt of gratitude that is owed to you. For the listening ear when I could not stop talking about my thesis in the good times, for the distraction when I needed it in the not so good times, for the good coffee at all times, and for the wisdom at the right times, thank you.