The mouse on the right has been engineered to have four times the muscle mass of a normal lab mouse. A drug to achieve the same effect was recently tested in space.
Se-Jin Lee/PLOS One
https://www.npr.org/sections/health-shots/2020/09/08/910776985/drug-that-bulked-up-mice-in-space-might-someday-help-astronauts-make-long-voyage
