The best resistance training is free-weight training, for a marathoner, i would say core muscles are important, so i would recommend compound exercises like squats and deadlifts.
Runner's World has good general training programs geared towards those who want to run marathons. Also, Oxygen magazine is all about weightlifting with a focus on women.
Recently it has been shown that resistance bands are a very great addition to any exercise routine for both men and women. They give results very similar to free weights having resistance in all ranges of motion. Resistance bands allow for many reps yielding a great workout.
Female marathoners should not forget to include some form of weight training in their workout regimens but bodyweight routines such as fitdeck are most effective for runners.
Jogging will do a lot of good to ensure that the muscles are strong enough and your bones will carry your weight with ease. Involve also stretching exercises for the whole body so that you attain flexibility too.
