NoFrance writes "Russian cosmonaut, Sergei Krikalev has taken the record for most time spent in space away from fellow Russian Sergei Avdeyev. At 748 days in space, Krikalev has an impressive list of accomplishments to his name, including : back-to-back 6 month tours on mir, he flew on the first joint US-Russian space shuttle mission, and a member of the first crew to live on ISS. He is currently commander of the ISS in a six-month stint that began on 14 April. Most impressive is his ability to deal with the physical hardships in space. In space most people lose around 1.5% of their bone mass per month, even with a disciplined exercise regime. And growing the bone mass lost from a 6 month stint back, can take a long time."