Threshold training is a staple in every distance runner’s program from the 5K to the marathon. It holds the key to accessing more of your VO2max and hence faster race results.
“Threshold training lets you access more of your aerobic capacity.”
In other words, in distance events, a high VO2max provides the speed and a high lactate threshold provides the stamina to hold on to speed for longer.
What is Threshold Training?
Strictly speaking, there are 2 thresholds: The aerobic threshold and the anaerobic threshold.
The aerobic threshold is the point above which lactate levels start to accumulate significantly above baseline but the body still keeps up with lactate clearance. That happens roughly at a 2-hour race pace regardless of your training level. But while the world’s best runners can complete a marathon at this intensity, it’s somewhere between marathon and half-marathon pace for amateurs.
The anaerobic threshold is the point above which lactate accumulates faster than it can be removed. That represents a 1-hour race pace. For elite runners that’s half-marathon pace, amateurs around 15K pace, and beginners closer to 10K pace.
I refer to the anaerobic (lactate) threshold when speaking of threshold training here. The lactate threshold is one of the 3 most important performance determinants in distance running alongside VO2max and running economy.
The Benefits of Threshold Training
The main purpose of threshold running is the removal of blood lactate, of course. As you probably already know, lactate is an important fuel source. With tempo training, your body gets really efficient at directing blood lactate to the liver where it gets reconverted back into energy. So rather than an improved lactate tolerance, the aim is to get better at repurposing lactate.
That means threshold training enables you to run at a higher percentage of your VO2max, as I already mentioned before. But training at threshold intensities is also a potent stimulus for improving VO2max itself. In fact, training at the lactate threshold has a higher effect on increasing the number of capillaries in slow-twitch muscle fibers than VO2max intervals.
Other adaptations of threshold training regarding VO2max are increased blood plasma volume (including red blood cell count), the formation of new mitochondria, and a higher number of aerobic enzymes in slow-twitch and intermediate muscle fibers.
The Intensity of Threshold Runs
Lactate threshold (LT) intensity is well-defined. If you were to take blood samples at different intensities, you would know your LT pace arriving at 4 mmol/L. Of course, measuring your LT in a laboratory isn’t very practical. Especially because the lactate threshold should be evaluated every 3 to 4 weeks to accurately determine your training zones unless you have a recent race result.
Most athletes opt for the time trial method. After a thorough warm-up, run for 30min at the fastest pace that you can sustain. Note your heart rate 10 min into the time trial and at its end. Then divide them by two. That’s your lactate threshold heart rate. Your lactate threshold pace is the average of the entire 30 minutes.
Now I hear you asking: “Didn’t you just say LT is your 1-hour race pace?” It is. But first, your legs aren’t fully rested like after a pre-race tapering, and second, your mental state is different on a solo training run than in a race with a potential personal record or seasonal best at stake. For that reason, a 30-min time trial reflects a fairly accurate picture of your current lactate threshold.
The classic workout is the tempo run right at lactate threshold intensity. But research has shown that paces slightly under and above LT are also effective. In my training plans, I schedule paces slower than LT first (e.g. marathon pace, 30K-pace, and HM-pace) rather than introducing tempo runs out of nowhere. Depending on the race distance, 10K-pace can be a great stimulus for further lactate threshold development too, especially lactate tolerance.
The Duration of Threshold Runs
Tempo training can be continuous (20 – 30 min) or intermittent where short bouts are followed by a recovery period. Continuous tempo runs have the benefit of exposing your body to systemically high lactate levels for a prolonged period of time. Tempo intervals, by contrast, include a short relief period of easy running which enables you to accumulate more time at LT in total.
But as I mentioned before, rather than starting out with low mileage at the lactate threshold, I recommend building up to at least 30 min of running at the aerobic threshold (~30K pace). That way, you bridge the gap between easy runs and lactate threshold by developing the necessary direct endurance support for solid tempo runs.
Once that is accomplished, a 20 min tempo run shouldn’t pose a challenge. Advanced runners can extend tempo runs to 30 min or 2x 15 min with a 90-sec jog in between. Beyond 30 min lactate threshold training certainly becomes masochistic and interferes with upcoming training sessions. At least at the amateur level.
How Often Should Your Run at Threshold?
The optimal frequency of tempo runs for amateur runners is once a week. If you are training with performance goals in mind you likely have 3 key workouts: VO2max intervals, a threshold run, and a long run on weekends. The remainder is easy runs—or runs at a moderate pace at most—even if you run 7 days per week.
There are exceptions to it, of course. During the base period, there may be no threshold training at all. And during the race-specific period of 5K runners, there won’t be a dedicated threshold run either. In this case, LT training has to make way for more specific sessions from 3K – 10K pace. Those fast intervals are all above the LT and maintain the ability to process and tolerate lactate.
On the other hand, there are instances when threshold training can occur twice a week. Think of half-marathon training, where a high lactate threshold is close to HM race-specific pace and acts as direct speed support. Here a segment at the lactate threshold could be attached to the long run every other week.
The following runs are just a few examples of what threshold runs can look like in training. Each session should start with at least 10 minutes of easy running and end with a 5 – 10 min cool-down. Make sure they fit into the overall structure of your training plan.
Classic LT Tempo Runs
- steady effort 20 – 30 min at 15K pace (~10 mile pace)
- 3x 10min at 15k pace with 2 min jog recoveries
- 3 – 4x 1600m alternating every 1600m between HM and 10K pace with 1 min jog recoveries
- 3 – 4x 1600m (alternating every 400m between HM and 10K pace) with 1 min jog recoveries
- 15 min at HM pace + 10 min at 15K pace + 5 min at 10K pace with 2 min jog recoveries
- 2x 12 min at 15K pace + 5 min at 10K pace with 2 min jog recoveries
The above tempo runs are merely suggestions for the intermediate/advanced runner. Adjust them to your training level.