Dietary protein, physiological condition and metabolic amino acid utilisation

This thesis describes the investigated effects of the level of dietary protein intake and the physiological condition of the animal on the percental oxidation of leucine. This measure reflects which part of the free leucine pool was used for protein and energy metabolism. The employed technique consisted of a constant infusion of 14C-leucine and simultaneous collection of expired 14CO 2 . The aim of the study was to identify the causes and objectives of amino acid losses and therefore the metabolic basis for their requirements. The percental oxidation of leucine was decreased in the postabsorptive state by chronic protein restriction, growth and pregnancy, and was increased by a period of fasting, meal frequency and exercise. The transition from the postabsorptive to the postprandial state caused an increase in expired 14CO 2 . The percental oxidation in the postprandial state increased with the protein content of the meal. During different phases after the meal the percental oxidation was decreased by growth and pregnancy (2-4 h), chronic protein restriction (4-6 h), and training (6 h) and increased by the period of fasting (6 h). Several other aspects, such as the level of leucine intake, the use of tracer isotopomers, duration of tracer infusion, and the route of tracer administration were investigated. From these studies it was concluded that there is a large diurnal variation in amino acid losses, which have to be accounted for in the estimation of nutritional requirements

Attitudes of Older Adults in a Group-Based Exercise Program Toward a Blended Intervention:A Focus-Group Study

Ageing is associated with a decline in daily functioning and mobility. A physically active life and physical exercise can minimize the decline of daily functioning and improve the physical-, psychological- and social functioning of older adults. Despite several advantages of group-based exercise programs, older adults participating in such interventions often do not meet the frequency, intensity or duration of exercises needed to gain health benefits. An exercise program that combines the advantages of group-based exercises led by an instructor with tailored home-based exercises can increase the effectiveness. Technology can assist in delivering a personalized program. The aim of the study was to determine the susceptibility of older adults currently participating in a nationwide group-based exercise program to such a blended exercise program. Eight focus-groups were held with adults of 55 years of age or older. Two researchers coded independently the remarks of the 30 participants that were included in the analysis according to the three key concepts of the Self Determination Theory: autonomy, competence and relatedness. The results show that maintaining self-reliance and keeping in touch with others were the main motives to participate in the weekly group-based exercises. Participants recognized benefits of doing additional home-based exercises, but had concerns regarding guidance, safety and motivation. Furthermore, some participants strongly rejected the idea to use technology to support them in doing exercises at home, but the majority was open to it. Insights are discussed how these findings can help design novel interventions that can increase the wellbeing of older adults and preserve an independent living.