In the UK, the percentage of people aged 65 years and over increased from 15 – 17% (1.7 million) between 1985 and 2010. Furthermore, it is projected that by 2035 people aged >65 years will make up 23% of the UK population, with those aged >85 years accounting for 5% of the total population (1). Increased life expectancy does not necessarily increase health expenditure, but ill-health in the final part of life certainly does, and on average adults in the UK spend the last decade of life in ill-health. Ageing is associated with a progressive decline in muscle metabolic health and functional capacity, leading to a loss of independence. This presentation will describe the changes in muscle mass, strength, fibre composition, power, oxygen utilisation and insulin sensitivity that occur with ageing in humans, and will identify mechanisms that potentially explain these negative changes. In particular, given ageing is associated with increased sedentary behavior, consideration will be given to whether the biological features attributed to muscle “ageing” per se may in fact be a consequence of previous and/or current levels of physical inactivity. Indeed, data will be presented showing that many of the purported negative effects of muscle ageing can be relatively quickly manifested in young people simply by exposure to inactivity. Current knowledge gaps include the relative contribution that physical inactivity plays in the development of many of the features associated with poor muscle metabolic health in older age, including muscle centric mechanisms linking physical inactivity and/or sedentary time to impaired metabolic health. Similarly, data demonstrating positive effects of government recommended physical activity guidelines (or indeed any other physical in/activity interventions relevant to preservation of health) on muscle specific health, the decline in which is strongly associated with functional deterioration in older adults, are largely non-existent. It is imperative therefore that research examining interactions between ageing, physical activity and muscle metabolic health is prioritised so that it can that inform on the “normal” muscle ageing process and on strategies for improving health span and well-being.