To learn more about what's happening on the International Space Station at any given time, check out NASA's frequently-updated ISS blog or their page about the research and development work happening on ISS.
Depends on your body type and metabolism and your routine. But usually it takes around 3 to 4 weeks for visible results. For me it took me a couple of months to actually see any progress visually.
But how long defines a day, and what about other forms of exercise? Whether you're a casual or highly competitive athlete, waiting at least 12 hours after giving blood before resuming your normal exercise schedule helps you rehydrate and rebuild strength.