I saw this abstract today. As you get older you lose muscle - sarcopenia they call it. It is a bad thing because it sets you up for injury. Muscle is also useful to the body metabolically too as a reservoir of nutrients and reserves. Anyway, maintaining your muscle mass as you age is very beneficial.
My normal assumption is that people lose muscle because they become less active. Old people exercise less.....if only they would keep training then this would be better.....
This abstract of a study makes things a little more depressing. The problem seems to be down to metabolic changes - people become resistant to anabolic stimuli - i.e. the exercise that used to make you grow muscle becomes ineffective. The study relates to endurance exercise. I wonder if it would apply equally to resistance training?
Age-related anabolic resistance after endurance-type exercise in healthy humans
Age-related skeletal muscle loss is thought to stem from suboptimal nutrition and resistance to anabolic stimuli. Impaired microcirculatory (nutritive) blood flow may contribute to anabolic resistance by reducing delivery of amino acids to skeletal muscle. In this study, we employed contrast-enhanced ultrasound, microdialysis sampling of skeletal muscle interstitium, and stable isotope methodology, to assess hemodynamic and metabolic responses of older individuals to endurance type (walking) exercise during controlled amino acid provision. We hypothesized that older individuals would exhibit reduced microcirculatory blood flow, interstitial amino acid concentrations, and amino acid transport when compared with younger controls. We report for the first time that aging induces anabolic resistance following endurance exercise, manifested as reduced (by approximately 40%) efficiency of muscle protein synthesis. Despite lower (by approximately 40-45%) microcirculatory flow in the older than in the younger participants, circulating and interstitial amino acid concentrations and phenylalanine transport into skeletal muscle were all equal or higher in older individuals than in the young, comprehensively refuting our hypothesis that amino acid availability limits postexercise anabolism in older individuals. Our data point to alternative mediators of age-related anabolic resistance and importantly suggest correction of these impairments may reduce requirements for, and increase the efficacy of, dietary protein in older individuals.