Skeletal muscle properties show collagen organization and immune cell content are associated with resistance exercise response heterogeneity in older persons

Abstract

Extensive analyses of muscle features associated with muscle size and resistance training response in older persons, including sex differences, and evaluation of multiple measures of hypertrophy are discussed. New skeletal muscle features, such as collagen organization and CD11b-expressing immune cells, both CD206+ and CD206−, offer potential new targets to increase resistance training response in older individuals. A composite score using three indices of muscle growth reveal that changes in immune cells, myonuclei, and capillary density are critically important for overall muscle growth in older persons. Evidence exists for macrophage heterogeneity.