Habitual Physical Activity Assessment Using Objective Measuring Devices: Observations in Lean and Obese Adults and Children

Abstract

ABSTRACT Physical inactivity is one of the major public health problems in many parts of the World. In Scotland it is reported that two thirds of Scottish adults (>16yrs) and one third of Scottish children (<16yrs) do not do sufficient physical activity to gain the health benefits of physical activity. Furthermore, there is still much debate about the nature and volume of physical activity required to provide health benefits. Therefore, more investigations are required to help improve our understanding of the links between physical activity, obesity and health. In addition, the assessment of habitual physical activity needs to be accurately quantified using appropriate methods that are valid and reliable. The main aims of this thesis were thus to assess the validity and reliability of three new generations of movement sensing devices (Actigraph, ActivPAL and SenseWear PRO2) in adults and adolescents in a controlled laboratory environment and to then use the most valid and reliable device in assessing the habitual physical activity of adults (lean and overweigh/obese) and adolescents in a free-living situation. Following objectively assessing the habitual physical activity, investigation of the associations between physical activity status and cardiovascular and metabolic disease risk markers in adults and adolescents were the last main aims of this thesis. In the first study, the results indicated that the new generations of the three devices were reliable in assessing EE during walking on the flat and on a 5% incline in lean and overweight/obese adults and lean adolescents. However, none iii of these devices and the methods or programme versions that were selected and applied was able to accurately estimate EE during walking on a treadmill. However, based on the sensitivity data obtained and previous evidence, the Actigraph was considered the most appropriate device for assessing the habitual physical activity due to its ability to discriminate between physical activity intensities. The second and third studies concluded that adults (including lean and overweight/obese) met the recommended physical activity guidelines for health and wellbeing purposes. However, the data suggest that overweight/obese participants may need to be advised to spend more time in MVPA and probably more vigorous activity to not only reduce body fat but also to increase cardiorespiratory fitness and reduce their chances of future cardiovascular and metabolic disease. The fourth and fifth studies, demonstrated that the Scottish adolescents –in the cross sectional study- were below the recommended physical activity guidelines. When the method of physical activity assessment was adjusted the Scottish adolescents were similar to the adolescents in other European countries and were observed to be more active than adolescents in some of the developed countries such as American adolescents (Texas State). In the case of lean adolescents who have a low physical activity- but who are not sedentary- the cardiovascular and metabolic disease risk markers may not be obvious at this stage, but the differences in glucose and HOMA-IR suggest that there may be early signs of progression towards metabolic disease in this group. iv The importance of the associations between vigorous physical activity and body fat, as well as between body fat and the risk markers of metabolic disease, suggests that future intervention studies should focus on monitoring the outcome from vigorous physical activity interventions vs. moderate activity within current guidelines.