lots of sit ups are good. pilates is excellent and so is fitball.
you won't feel as tired as quickly if you've got a strong core, and towards the end of your marathon your stride is less likely to chop if all your deep stomach and groin muscles can still push the levers when you're tired.
do an exercise class with the ball. you'll run straighter and taller and your balance will improve which helps if you tend to land funny when tired. I started to see a real benefit after just 6 weeks of once a week classes.
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you won't feel as tired as quickly if you've got a strong core, and towards the end of your marathon your stride is less likely to chop if all your deep stomach and groin muscles can still push the levers when you're tired.
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