It’s not just your muscle & bones that you’re building with exercise… it’s your immunity niches where immune blood cells are formed in your bone marrow!
Scientists at the Children’s Medical Center Research Institute at UT Southwestern (CRI) have identified the specialized environment, known as a niche, in the bone marrow where new bone and immune cells are produced. The study, published in Nature, also shows that movement-induced stimulation is required for the maintenance of this niche, as well as the bone and immune-forming cells that it contains. Together, these findings identify a new way that exercise strengthens bones and immune function.
https://medicalxpress.com/news/2021-02-mechanism-bones-immunity.html