Age-related changes in muscle architecture and metabolism in humans: The likely contribution of physical inactivity to age-related functional decline.

In the United Kingdom (UK), it is projected that by 2035 people aged >65 years will make up 23 % of the population, with those aged >85 years accounting for 5% of the total population. Ageing is associated with progressive changes in muscle metabolism and a decline in functional capacity, leading to a loss of independence. Muscle metabolic changes associated with ageing have been linked to alterations in muscle architecture and declines in muscle mass and insulin sensitivity. However, the biological features often attributed to muscle ageing are also seen in controlled studies of physical inactivity (e.g. reduced step-count and bed-rest), and it is currently unclear how many of these ageing features are due to ageing per se or sedentarism. This is particularly relevant at a time of home confinements reducing physical activity levels during the Covid-19 pandemic. Current knowledge gaps include the relative contribution that physical inactivity plays in the development of many of the negative features associated with muscle decline in older age. Similarly, data demonstrating positive effects of government recommended physical activity guidelines on muscle health are largely non-existent. It is imperative therefore that research examining interactions between ageing, physical activity and muscle mass and metabolic health is prioritised so that it can inform on the "normal" muscle ageing process and on strategies for improving health span and well-being. This review will focus on important changes in muscle architecture and metabolism that accompany ageing and highlight the likely contribution of physical inactivity to these changes.

"Exercise as medicine" in chronic kidney disease.

Exercise and physical activity are increasingly becoming key tools in the treatment and prevention of several medical conditions including arthritis and diabetes; this notion has been termed "exercise as medicine". Exercise has favorable effects on reducing cardiovascular risk, inflammation, cachexia, and hypertension, in addition to increasing physical functioning, strength, and cardio-respiratory capacity. Chronic kidney disease, a condition that affects around 10% of the population, is often overlooked as a target for exercise-based therapy. Despite the vast range of severity in kidney disease (e.g., pre-dialysis, dialysis, transplant), exercise has a potential role in all patients suffering from the condition. In this review, we summarise the important role exercise may have in the clinical management of kidney disease and how this form of 'medicine' should be best administered and 'prescribed'.