I was just watching Star Trek: Into Darkness, and I noticed that James Kirk and Spock were both showing incredible feats of physical fitness. Both of them managed to climb obstacles with only their arms pulling up their entire body weight (Kirk climbing up to realign the warp core, Spock clambering up the side of two unidentified red ships). I was also very impressed by Spock running at a dead sprint for several extended minutes.
It seems like officers aboard a starship wouldn't have opportunity to hone these skills. Even if they were forced to do so in some kind of "basic training" equivalent, they would quickly atrophy with no upkeep. So I was wondering if there's any real in-universe explanation for them being in such good shape (really, remarkable fitness, not just passable fitness).