Getting your running style correct for maximum performance and avoiding injury are two key factors a marathon runner has to keep front of mind whilst focusing on their journey.
Strong core stability will help with all aspects of movement and in particular with running and any form of exercise. A strong core will distribute the stresses of weight bearing and protect the back. Core stability relates to the muscles which stabilise the spine, pelvis and shoulder and these provide a solid foundation for movement in the arms and legs. It will also protect the body from the effects of repetitive motions.
Stretching and strengthening exercises are the key to a strong core and the best example of this is the ever popular Pilates which is based on strengthening the abdominal muscles and those in the lower back. This should be coupled with weekly circuit training and resistance training for an all round workout which will protect from injury.