If you use your iDevice for watching videos using the built-in, stock Videos app, you may have noticed that the only way of fast forwarding or rewinding is the positioning slider at the top. You “grab” the slider with a finger and drag it to the left/right to rewind / fast forward, respectively.
Additionally, you can also drag your finger downwards to make the slider dragging speed slower. It won't help much when you run or do some other exercise and, in order to keep your pulse high, wouldn't want to stop it.