The treadmill serves as a great training tool to control the exact intensity you need in the moment. One thing that is rarely practiced in training that happens more often than not in a race is a "surge" of intensity. This workout focuses on practicing surges or "spikes" then returning to your threshold.
We'll start with a 10:00 section of easy running followed by a 3:00 pickup to your half marathon pace. After the pickup, resume running easy for another three to five minutes before we start the workout.
This workout can be thought of three repeats in one. The basic structure we'll follow is 4:30 at your threshold, 1:00 at your 10k effort, then another 4:30 back at your threshold. For this workout you can use your hour race pace, or half marathon pace as threshold. You'll complete three sets of these repeats, with 4:00 easy jogging between sets.
After you finish your third set you'll jog easy for 15:00 to finish the workout!