Depending how far you are out of shape. First step would be to consult a Doctor, and explain what your plannig to do , and follow his advice to get in shape. When you do ride start out slow and easy. Don't worry too much about distance and speed. Keep it up daily, every so often try for a longer distance, and a higher speed. Don't up them too far, a little at a time when the ride gets easy. This will get you going with the least amount of problems.