Zero-G Pill?
http://www.signonsandiego.com/news/business/biotech/20080801-9999-1n1gene.html
Discovery at Salk Institute makes ordinary mice run like marathoners
"I believe the availability of drugs that could stimulate the effect of exercise could reduce muscle wasting or atrophy,†Evans said."
Very interesing discovery. This line of research could have applications in keeping muscles toned in Zero-G and opening the low gravity planets to long-term colonization.