RE: What is bumping?
Dear Marisa,
I think that cardio and strength in the same day can be widely interpreted. Remember, walking to school and playing on the monkey bars are cardio and strength. Overtraining, however, is a real risk and I have found trial and error to be the best way to figure out whether I'm overtraining.
From a functional standpoint, few demanding physical activities in life are exclusively cardio or strength. Therefore it is good to train with both so we have all the ability that we need to perform tasks of daily life, with some left over.
Sometimes a person might want to focus more on a certain weak area. Then it's a good idea to devote an entire session to that area, be it cardio, or strength in one or more body part, or something else.
One reason people say strength and cardio are not good on the same day is that cardio uses up matter in your body as fuel. Usually we imagine that it's only fat, but actually water, muscle tissue and even bone turn into energy to fuel cardio. With the type of working out most of us do (all Cathe's workouts throughout the year), the amounts are miniscule enough to be insignificant. Even less if we eat a good mix of foods.
People trying to bulk up at all costs may shy away from cardio because it can interfere with building big muscles, especially people in a hurry. However, most of us here are at least as interested in fitness for its own sake, as for looks, and in it for the long haul.
In sum, I think cardio and strength in the same day is not bad.