This popular science article covers some of the major research topics related to sarcopenia, the loss of muscle mass and strength that occurs with age. A great deal is known of the biochemistry of muscle aging, the signals and mechanisms involved in muscle stem cell activity and muscle growth, and how they change with age. A great deal more remains to be discovered, and fitting together what is already known into a coherent whole is a still a work in progress. Any proposed layering of cause and effect is speculative at best, and it is usually unclear as to where exactly any newly described signal or mechanism fits. It it is probably the case, here as elsewhere, that the fastest path to improved knowledge is to start in on manipulating the aging of muscle: adjust a mechanism in isolation of the others and analyze the results.
Up to a quarter of adults over the age of 60 and half of those over 80 have thinner arms and legs than they did in their youth. The good news is that exercise can stave off and even reverse muscle loss and weakness. Recent research has demonstrated that physical activity can promote mitochondrial