I've heard of the "10 Percent" rule for increasing distance when running - something like "don't increase your distance for a single run or for the entire week by more than 10 percent per week". Is there a similar rule of thumb for increasing pace?
If pace can be considered intensity of the workout, then this article believes that pace should be slowly increased as well:
Increasing the intensity, time or type of activity too quickly is one common reason for sport injury. To prevent this, many fitness experts recommend that both novice and expert athletes follow the ten percent rule, which sets a limit on increases in weekly training. This guideline simply states that you should increase your activity no more than 10 percent per week. That includes distance, intensity, weight lifted and time of exercise.
However, certain types of exercise, such as interval training, relies on judicious use of high intensity activity interspersed with lower intensity activity, so this "10% rule" is more of a guideline since each person's body has a unique tolerance for workout intensity.