Muscle architectural and physiological responses to immobilisation: impact of age and obesity

Clinical scenarios of recovery from illness or injury both require acute, mandatory periods of bed rest or immobilisation. However, this inevitably leads to; muscle loss, muscle weakness and a number of negative health problems which may be exacerbated in the elderly and in the obese. Both ageing and obesity are accompanied by reduced habitual physical activity levels and impaired muscle metabolic health which may pose an additive burden on musculoskeletal health in these patients. Therefore, understanding musculoskeletal deterioration associated with immobilisation is a major public health issue and embodies a vital area for scientific investigation. This thesis describes a series of human volunteer studies performed to elucidate the short-term (3 days) and longer-term (14 days) impact of muscle unloading on muscle metabolic and physiological health in healthy young and older, normal weight and obese volunteers The major findings were: 3 days of unilateral lower limb immobilisation in healthy normal weight young and older volunteers supressed myofibrillar protein FSR by ~25% (p<0.01) and ~22% (P<0.05) respectively when compared to the non-immobilised limb at baseline, whilst this was not apparent in healthy young obese volunteers. In addition, ultrasonography-determined medial gastrocnemius muscle volume declined during immobilisation in the young normal weight group and the young obese group by ~7% (p<0.05) and ~15% (p