I once coached a runner who ran a 19-minute 5K who told me she wanted to be trained like a 17:30 5K runner. So, I told her to run a 17:30 5K and then I’ll train her like a 17:30 5K runner.
It seems logical that if you want to run a race faster, you should practice by running at that faster pace. But, there are a few problems with this way of thinking. For starters, what determines goal pace? A runner’s race time goals are often arbitrary and not in agreement with what is realistic. I have coached many runners over the years who had unrealistic goals. If I had prescribed them workouts at their goal race paces, those workouts would have been way over their heads, and they would have run themselves into the ground trying to accomplish them.
Secondly, running at goal race pace represents a future level of fitness. Doing workouts now at that future fitness level means that you’re doing workouts faster than what you need to run to meet the desired purpose. For example, if that 19-minute 5K runner did her lactate threshold workouts based on a 17:30 5K, her workouts would no longer have been purely aerobic; they would have become anaerobic, which would have changed the desired purpose and the stress of the workouts.
Thirdly, running at goal race pace moves you away from targeting the specific physiological factors that dictate running performance. You’ll no longer be training at lactate threshold pace to train lactate threshold, or VO₂max pace to train VO₂max. It’s better to target physiological factors than to train at arbitrary paces. Run only as fast as you need to meet the purpose of the workout.
This doesn’t mean you should never train at goal pace, but do it sparingly, only for psychological reasons to give you confidence, and only when the goal is realistic for that season.