It depends... on many factors. If you are talking about box rated film speed then here is some observations.
Originally Posted by jsimoespedro
If you are using medium format, regardless of Box rated ISO speed, depending on the illumination of the subject matter, when pushing, you will see less shadow detail, which may appear as high contrast.
If you are using medium format, slower ISO 100 and below film, you will not likely see a grain difference except under enlargement over 8x10 when pushing.