"Biogerontology" is the subfield of gerontology dedicated to studying the biological processes of aging. It includes "Biomedical gerontology," also known as "experimental gerontology" and "life extension", is a sub discipline of biogerontology that endeavors to slow, prevent, and even reverse aging in both humans and animals. Curing age-related diseases is one approach, and slowing down the underlying processes of aging with the help of physical exercises is another. Most "life extensionists" believe the human life span can be altered within the 21st century.