mtnbiker7 saidI've been trying to flatten my stomach and lose about 20 pounds. Biking is not doing it..Been told that running will do the trick, but I've always been unsuccessful because of shin splints. Any advice on shoes, surface or form will be greatly appreciated. I'm 49, weigh 165-70, 5'8", and had aortic valve replacement surgery about 3.5 years ago. I have no restrictions on activity, so it's just a matter of getting off my ass and doing it.
If biking isn't doing it, then running won't either. The only thing running changes is the amount of calories burned during a given time frame; but remember, because you're not used to running you're not going to be able to do it for as long, at least for a while. They're just two forms of cardio, the only difference being the amount of calories burned per hour for each exercise, though even that depends on the intensity level of the exercise.
If you want to get your weight down, you have to get your diet in order; you may already be doing things right on your diet, I really don't know. I'm also not as well versed as others here on what you need to be eating and how much (I'm experimenting myself). Are you also weight training? If you're not, you should be; cardio alone will almost surely not get you to your goal. Lean muscle mass is hugely important, since extra muscle mass makes your body naturally burn more calories at rest.
Those are a few thoughts; really, if running causes shin splints for you then it might just not be the right exercise for you. It's more important to find a cardio exercise that your body can tolerate and that you enjoy than worrying about doing the "right cardio;" add in weight training and get your diet in order, and those are the things that are really going to go a longer way in helping you with your goal.