A couple months ago, I wrote about what tempo runs are and why they are important for training. Today, I want to discuss a specific type of tempo run: threshold intervals. Between all you hear about shorter interval repeats and traditional tempo runs, threshold intervals do not get a lot of attention. However, threshold intervals offer tremendous benefits to your running, whether you are in the last few weeks before a 5K or 10K race or training for a half or full marathon.
Threshold interval are essentially tempo runs cut into pieces with a bit of recovery in between each interval. Adding in the recovery intervals decreases the stress running at a hard pace places on your body, thus maximizing your training while minimizing your risk of injury. They were popularized under the similar names of “cruise intervals” by running coach Jack Daniels and “tempo intervals” by running coach Greg McMillan. Cruise intervals are typically shorter in duration than tempo intervals, but since they are both run at threshold pace, both are a type of threshold interval.
What do I mean when I say threshold? Threshold refers to a specific pace in training. Jack Daniels, who has his PhD in exercise physiology and wrote perhaps the greatest running book of the 20th century (Jack Daniels Running Formula), devoted a lot of his research and makes his athletes devote a lot of their training to threshold pace. Daniels describes threshold pace as the pace where if you go any faster, your blood will being to accumulate lactic acid at too quick of a rate and you’ll become quickly fatigued. Since threshold paces pushes that fine line, training at it teaches your body to better remove lactic acid and in turn run for longer at faster distances.
Threshold pace, also known as tempo pace, is very closely related to your 10K to half marathon pace. When you run traditional tempo runs, you are usually running somewhere around your 10 miler to half marathon pace. When you sprinkle in brief intervals of recovery, as you do in threshold intervals, you can run slightly faster for slightly longer without accumulating excess lactate. So your pace for threshold intervals is at the higher end of your lactate threshold, usually around your 8K to 10K pace.
So threshold intervals are repeats at roughly your 8K to 10K pace. To maximize the benefits of the workout, you keep your recovery between the intervals short, usually 1-5 minutes depending upon the duration of the interval. Since these are longer intervals, you don’t do a lot of repeats; depending on the distance, you will only run 2-4 repeats.
So, for example, a common threshold interval is mile repeats run at 10K to half marathon pace. Threshold intervals usually last anywhere from ½ mile (800 meters) to 3 miles, depending on for which distance you are training. McMillan and the Hansons brothers (the coaches behind the popular Hansons Marathon Method) both recommend a workout of 2-3 x 2 miles @10K or 10 mile pace with a short recovery. The total duration of work at threshold pace is 3-6 miles during these workouts.
The Hansons Marathon and Half Marathon Methods actually use threshold intervals on a weekly basis during the second half of the training plan, which is probably one of the reasons runners experience such success off of their plans. Threshold intervals take the place of shorter and more intense speed intervals (your traditional 400m-1600m track workouts) for longer and less intense threshold intervals ranging from 6 x 1 mile to 2 x 3 mile.
Why should you run threshold intervals? This adaptable workout offers a multitude of benefits for runners. For runners transitioning from base-building season to specific race training, threshold intervals help prepare their bodies for harder and longer efforts such as long runs and tempo runs. For runners preparing for 5K and 10K races, threshold intervals offer both the benefits of shorter track workouts, such as improved running economy, and of tempo runs, such as increased lactate threshold.
Threshold intervals teach your muscles and your mind to work through the discomfort of lactic acid accumulation. While you do not accumulate as much lactic acid as you would during a tempo run, you still accumulate enough to experience discomfort. By teaching yourself to run through that discomfort, you are preparing your mind and body for the last few miles of the race. Like tempo runs, threshold intervals also train your muscles to remove lactic acid at a faster rate, thus helping improve your ability to run faster for longer. Additionally, threshold intervals improve how efficiently your body is able to use energy when you run.
Threshold intervals also teach you how to pace yourself, which is essential for runners of all distances. The pace may seem easy during the first interval, but if you go out too fast you will struggle to keep the pace by the last interval!
Want to try a threshold interval workout? I have one to share with you! As with all tempo and speed workouts, you want to begin and end with at least a mile warm-up and cool-down. Warming up and cooling down eases your body into and out of the harder effort, which helps you hit your paces and reduces your risk of injury. For newer runners, I suggest running at your half marathon pace; for more advanced runners, run these around your 10K pace or 10K pace plus 10 seconds. While you could do this workout on a track, a larger loop or stretch of road is better both mentally and physically!
Have you ever used threshold intervals in your training?