Cross training is a theme that is in every Runner's World edition in some shape or form but I still truly believe is the last thing most runners consider and if we do even dwell for a moment on it - it is the form of another sport such as swimming or biking or yoga. All three are fabulous and should be considered, but they are not the same as a cross training. Swimming is not weight bearing - which is helpful for being a rest option but for overall tone and development it does not demand the same muscle recruitment as squats, lunges and all variety of exercise forms.
Now I'm not promoting Ms. Michael's as the be all and end all of exercise videos, but I think that she's also a good option. It's challenging but not long and exhausting in the format and there is enough variety that even someone like myself with a case of ADD when it comes to certain activities it works. So whatever you do whether it's a toning class at your gym or a DVD at home - just keep moving, every action will help.
Her DVD's are available in stores or online - I purchased a season from iTunes.