GOOD FOUNDATION FOR MUSCULAR STRENGTH CAN BE DEVELOPED THROUGH RESISTANCE TRAINING.
Although distance runners do not generally need a large amount of muscle bulk, it is still important to have strong musculature and good overall power. Resistance training is an extremely effective way of achieving this, and is also good for your overall fitness.
WHAT IS RESISTANCE TRAINING?
Resistance training is any type of training in which your muscles work against resistance. This might be provided by a weight, a rubber band, or your own body weight.
WHAT ARE ITS BENEFITS?
The main focus of this training is to build your overall strength, and it is good for toning some of the key muscles for running. It also burns fat and helps improve your general fitness; you may enjoy the variety it brings to your training schedule.
This program is aimed at runners with less than 2 months of resistance or core training experience. It is intended to provide an introduction to the basics of resistance training, and to give you a solid foundation of strength that can be built upon with more advanced exercises later in your training.
The intermediate program is designed for runners with 2–12 months of resistance or core training experience. It includes exercises of medium intensity that will increase your strength and familiarize you with the correct movement patterns. It can be incorporated into a training schedule for moderate-distance races.
You should undertake this program if you are a runner with more than 1 year of resistance or core training experience. The exercises are generally more demanding than the intermediate program and are designed to help you build a high level of muscular strength.
Taken From "The Complete Running and Marathon Book" -- OmRiyadat