question about exercise other than biking
the story: i used to ride a lot. avg probably 5 40+ mile rides per week. i loved it. wish i could still do it. alas, i'm in my first year of grad school and just don't have the time. plus it's becomming pretty cold in ann arbor and i'm a wimp. so i've started swimming a lot b/c i can't run and the pool is close to my library. swimming certainly seems like a great aerobic workout (meaning i can make myself short of breath pretty easily). obviously it doesn't work the legs in the same way as biking does, but it certainly seems to work the lungs and the heart.
my question is: when i go back to riding a lot (may 11th; after my big exam; can't hardly wait), assuming i keep at the swimming pretty good til then, will i be in ok bike shape? obviously the legs will need a good shakedown, but do you think the swimming wil help? i won't be off the bike completely between now and then, but i havn't taken a long ride in the last 2 weeks and it doesn't look like that rate'll change much in the near future. i guess my general question is: is there much benefit to cross training in the winter? i know i won't be able to jump right back in and be where i left off, but i'm just curious what to expect. any thoughts or opinions would be much appreciated.