Intense weight lifting, no more than 6 sets or so. Enough to get sore, not enough to break a sweat. Shower at night. Well over half the battle to stay fit is showing up to the place of exercise: even 2 sets at high enough intensity is enough to maintain and grow a fitness base. It took me a long time to optimize for it. I live in the Northeast, so if it's a hot summer's day, occasionally I do have to cut it short earlier and get in a shower. Sometimes I miss the train and have to take the next one - I try to take fewer breaks in the day to make up the lost 20 min. or so. ;-)