Exercise can help anyone and everyone if they set their minds to getting past the 'sedentary zone'. There are so many reasons why it doesn't make sense to remain sedentary but I will list a few: Heart Disease, Stroke and unnecessary muscle injury from lack of movement. There is also the commonly known but much neglected personal circumstances to consider when beginning an exercise program. Things you need to consider is posture, exercise history, exercise experience and past as well as present injuries.

You need a strong core to allow proper natural twisting and rotation of the pelvis without excessive twisting which could have negative consequences on speed as well as conservation of energy. Over twisting can be prevented by insuring that your arms are swinging from the shoulder joint rather than from the elbow joint. Think of the old fashion wild west movies when the two opponents are in a prepared stance to reach for their guns. The elbows are flexed at or close to 90 degree angles, hands relaxed and when they reach for their gun they will have to swing the elbow back to reach their hand to the handle of the gun in the holster. This action occurs from the shoulder. When the grab the gun from the holster they will once again swing the arm forward from the should causing the elbow to first swing back and then forward. They will not allow the torso to over-rotate nor will they allow the hands to over cross the midsection. This will make sure there aim is directed directly toward the opponent whom they intend to shoot before they get shot. The same is true about running in which it is important to pump the swing of the arms at the shoulders and not the elbows to avoid a hammering type appearance.
There are also considerations to be looked at during the stance phase and the swing phase of running. I will say that the most important part to watch for is over-striding which is seen during the swing to stance phase of the legs in which your foot lands to far ahead of your body. When this occurs you are hitting the breaks and slowing down your running so try and prevent over reaching during running. Your focus should be in such a way that your body is directly over your foot as you land to push off from the ground. If your foot is to far ahead you will find yourself pulling the ground rather than pushing the ground. This is dangerous because this can easily lead to a pulled hamstring. There is a whole science to proper running but I hope that these hints will be helpful in making you a better runner. :D
Keep in mind that the worse your form is the more likely you are to develop injuries and increase the magnitude of the injury as well. Also, your running form will either help you conserve energy or it will begin to deplete your resources at a faster rate. Knowledge is power when it is applied. Have a great running experience. :D
For more information you can go to: http://tworiverstreads.com/natural-running-form/
Look at magazines such as Runner's World and books like Running Anatomy, The Non-Marathon Trainer and Marathon: The Ultimate Training Guide.