“Threshold” is likely a term you’re familiar with if you have a running coach or are an advanced runner. If that’s not you…welcome to the mix. The short story? Threshold training is an important component of improving cardio fitness, and it’s pleasantly tough.
If the terminology is confusing (we get a little lost in the mix sometimes, too), I’ve put together this guide to threshold runs. To give you as much guidance as possible, I tapped experts Will Baldwin, a USATF- and VDOT-certified run coach, and James Rodgers, an endurance coach and competitive runner.
What Is a Threshold Run?
Brace yourself for a little (or a lot) of science. When defining a “threshold run,” we need to understand the various processes that occur in the body while running and how they relate to perceived effort levels.
Defining Threshold: Aerobic, Anaerobic, and Functional, Oh My!
If you’ve been researching threshold running, you’ve probably come across many different terms that include the word “threshold.” Here are common terms used in the running world:
- Aerobic Threshold (AeT)
- Anaerobic Threshold (AnT) and Lactate Threshold (LT)
- Ventilatory Threshold I (VT1) and Ventilatory Threshold II (VT2)
- Functional Threshold (FT or FTP)
Aerobic Threshold
Your aerobic threshold represents an effort level that you can maintain comfortably for hours. It’s a light- to low-moderate effort. Scientifically speaking, the aerobic threshold is the point at which the level of lactate in your body first starts to rise above resting levels and anaerobic metabolism pathways begin to assist with energy production. (1)
In other words, the aerobic threshold is your body’s tipping point. You’re flirting with the line between aerobic metabolism and anaerobic metabolism, but aerobic metabolism remains dominant—your body is still running on fats via oxygen metabolism.
AeT usually occurs at about 65 to 70 percent of your max heart rate, or heart rate zone 2.
Anaerobic and Lactate Threshold
The anaerobic threshold and lactate threshold are by and large the same thing. These terms describe the point at which lactate accumulation is beyond your body’s capabilities to clear it and your body switches over to primarily anaerobic metabolism instead of aerobic metabolism. This is also when fuel sources switch: Your body begins to tap into glycogen (carbohydrate) stores rather than rely on fatty acids. (2)
The important difference between AnT and LT is that AnT is found by measuring oxygen consumption levels, while LT is found by measuring blood lactate levels:
- When exercising at anaerobic threshold, your body begins to use more carbohydrate (glycogen) as fuel, as opposed to fats via oxidation. (3)
- Lactate accumulates in the muscle and is recycled for energy production, eventually “spilling over” into the bloodstream. Lactate threshold is reached when the athlete’s blood lactate volume reaches 4 mmol (4 millimoles per hour). (4)
[Read More: How to Build Stamina for Running]
Runners use anaerobic threshold as a predictor of race times because the pace that you can sustain at—or just below—your AnT/LT is the pace you can sustain for races. It typically occurs at about 80 to 90 percent of your max heart rate (also known as heart rate zone 4). (5)
Ventilatory Threshold I and Ventilatory Threshold II
VT is another way of measuring effort and energy metabolism. VT1 is the first point at which the athlete’s breathing becomes labored. It is associated with the aerobic threshold. (6)
VT2 is associated with the anaerobic and lactate thresholds; it refers to the point at which the athlete cannot maintain rhythmic breathing and there is a significant breakdown in controlled breathing patterns. At this point, the athlete is under significant physiological stress. (6)
Functional Threshold
Finally, your functional threshold pace (FTP) is typically defined as the maximum effort you can sustain for one hour. This is less of a scientific definition than a practical concept. To be clear, anaerobic threshold and functional threshold are not the same, though they are related. (7)
What Is Lactate and the Lactate Threshold?
When we talk about threshold running, the underlying understanding is usually that we’re talking about running at your lactate/anaerobic threshold. Let’s expand on the definition we covered above.
That may sound like mumble-jumble (and, really, you don’t need to remember all of those words), but the important thing to know is that “when we run hard, muscles move around lactate and lactic acid to help reduce the impact of fatigue,” says Baldwin.
This is a process known as lactate shuttling. “When we do a properly calibrated threshold run, our body can spend more time carrying out that process and eventually get more efficient at it,” he says. Importantly, “Lactate helps quell the fatiguing process, so we need just the right amount present,” Baldwin adds.
“If we run harder than our anaerobic threshold zone, there will be too much lactate present in our blood, and we won’t be able to clear out the fatigue fast enough,” he says. That’s when it starts to feel like your body is screaming at you to slow down or stop.
But by remaining in the anaerobic threshold zone, you’re running as hard as you can while clearing out most of the fatigue-causing metabolites, Baldwin explains. Thus, training in this zone eventually lends itself to the adaptation that all runners want: running faster for longer periods of time. (9)
Aerobic Threshold Run Vs. Anaerobic Threshold Run
So, if running at aerobic threshold and anaerobic threshold ultimately elevates performance, why would we need to do both?
Put simply, we do both because they train different energy pathways in your body, and as an athlete, it’s ideal for all energy pathways to operate at their maximum potential. That said, depending on your current fitness, your goals, and any events you may be training for, you might not need to do both.
For instance, a new runner should develop their aerobic capacity before adding anaerobic threshold training into their programming. Similarly, an athlete who needs to substantially improve endurance for long-distance events will be well-served by a training block that focuses on developing aerobic metabolism and later adding anaerobic threshold training back into their plan.
[Read More: The Best Sprint Workouts for Strength Athletes to Improve Conditioning and Power]
It may feel counterintuitive that you should run at the lower threshold effort to improve half-marathon and marathon race times. However, the concept is the same as that of zone 2 training: Running slower and maintaining a lower heart rate improves your body’s capability to use fats as fuel via oxidation—a critical component of long-distance racing. This is called improving your aerobic base. (10)
Utilizing higher-effort threshold work does improve your VO2 max and other markers of running performance, but lower-intensity training is important for long-term adaptation. (10)
Threshold Run Vs. Tempo Run
The terms “threshold run” and “tempo run” are sometimes used interchangeably. However, they’re not truly one and the same. Here’s an easy way to remember the difference:
Basically, a tempo run is just one type of a threshold run. Specifically, tempo running refers to maintaining your near-threshold pace for a longer period, usually two or more miles. Or, you can go by time rather than distance. For example, a workout plan may tell you to “run at near-threshold pace for 45 minutes.”
The key to a good tempo run is moving at a pace slightly beneath your true anaerobic threshold. For instance, if your threshold pace is 10 minutes per mile, you would perform your tempo run at a pace of 10:15 to 10:30 per mile, depending on how far you’re going.
Other popular threshold workout formats include:
- 3 to 5 sets: run 1 mile at threshold pace; walk or jog for 90 seconds between sets
- 2 to 3 sets: run 20 minutes at 5K pace; walk or jog for 5 minutes between sets
- 3 to 4 sets: run 2K at 10K race pace; walk or jog for 3 minutes between sets
Always warm up and cool down at a low-intensity pace when performing threshold runs.
How to Do an Anaerobic Threshold Run
Ready to implement threshold training? Here are some tips on how to get started.
First, Know When You’re Ready for a Threshold Run
As Baldwin explains, new runners can skip threshold running workouts for a while. Training at lower intensities for a few weeks is sufficient for improving your fitness level as a new runner. You may be ready to implement a threshold run after building an aerobic base for four to six weeks.
[Read More: Want to Learn How to Run a Mile Without Stopping? Tips From an Elite Coach]
This also applies for distance runners who need to improve their aerobic base. They’ll want to prioritize lower-intensity training—typically in zone 2, or 60 to 70 percent of your max heart rate—to improve aerobic capacity.
Determine Your Threshold Pace
There are a few ways to find or estimate your threshold pace.
Lab Testing
The most accurate method for determining your pace is to visit a sport science lab and undergo threshold testing, according to Rodgers. “You will then be provided with detailed information about your paces, heart rate zones, and current threshold level,” he says.
Max Heart Rate
Heading to a lab isn’t an option for everyone. It’s expensive, and such labs may not be available in your area. If you can’t get lab testing done, there are other ways to estimate your threshold pace.
One simple way, Rodgers says, is to use a percentage of your maximum heart rate. A common method is to use the pace at which you’re reaching 80 to 90 percent of your heart rate max (HRmax). For example, a 35-year-old with a max heart rate of 185 (220 minus age) would want to keep their heart rate below 166 for threshold running (166 is about 90 percent of 185).
[Read More: The Ultimate Guide to Heart Rate Variability and Strength Training]
“However, be aware this is very much an estimate, and you are better off underestimating your threshold heart rate than overreaching and risking being above your threshold,” Rodgers says.
Functional Threshold Pace
This is where your FTP comes in. Alternatively to the above two options, you can estimate the pace you could sustain for one hour, Rodgers says. “This is then the pace you should look to stay at or just under during your threshold running,” he says. “However, do take into account the weather and terrain you are running on. This is where another metric, such as heart rate, is useful.”
Considerations
Wind, heat, hills, and other environmental factors can affect your threshold pace for any given day. For instance, if it’s particularly hot outside, the effort required to run at the determined pace will be higher. Thus, your heart rate at that pace will be higher, pushing you out of your threshold zone. This is why using heart rate training is advantageous; we’re not performing our daily training in labs under optimal conditions, after all!
Plan Your Route and Aim for Ideal Conditions
To train at your true threshold run pace, your route should be flat and paved or hard-packed. Additionally, try to avoid running at hotter points in the day if training during the summer. If you have access to a treadmill, that can simulate ideal conditions.
[Read More: The Top Tips for Running on a Treadmill, According to Running Coaches]
Of course, it won’t always be possible to run on perfectly flat ground in perfect weather with no headwinds, so try not to stress too much if you encounter some unfavorable conditions.
Remember That It’s Not a Time Trial
Rodgers encourages runners to lose the mindset that every threshold run is a time trial—it isn’t.
“One of the most common mistakes that runners of all abilities make is running their threshold runs too hard, sometimes treating them as a time trial,” Rodgers says. “This defeats the purpose of the threshold run, and you no longer get the intended benefit, as you are likely to exceed your lactic threshold and the purpose of the workout is lost.”
How to Program Anaerobic Threshold Runs
The ideal frequency and volume of threshold runs depend largely on your current fitness and your primary sport. Here’s an overview of how to program threshold runs for different types of athletes.
For Beginners
Baldwin encourages new runners to hold off on lactate threshold training until they’ve increased their running volume to a few comfortable aerobic runs per week.
“You don’t necessarily need a lot of this type of work until you’ve been running regularly for a few weeks,” he says. “If you’re just starting up jogging, easy runs at a very low effort will be more than enough training load to improve from. I’d wait until you’ve been running for a month at least three times a week before I’d start assigning the work.”
At that point, you’d ideally start with one anaerobic threshold run per week, gradually building up volume over time. To increase volume, you can increase the length of your once-per-week LT run (e.g., do four sets intervals instead of three), add a second LT run, or both.
For Strength Athletes
For someone who’s primarily a strength athlete, Baldwin says he would program just one threshold session a week, and prioritize it as a run alone—not a combined workout.
“It’s really easy to run too hard and get outside our threshold zone, so we must be particular about how it’s performed,” he says. “It’s best to do it on flatter terrain where we can really monitor our effort and heart rate. Depending on the athlete, I might even use this as our longest run of the week.”
[Read More: How to Balance Running and Strength Training, No Matter Your Goals]
The reason for this, Baldwin explains, is that strength athletes receive other hard stimuli throughout the week, and overdoing threshold training could create an imbalance in their training profile.
Additionally, strength athletes may want to perform threshold runs on a treadmill to control pacing, says Rodgers. Because they may be less experienced with maintaining pace and effort outdoors, Rodgers says that treadmill threshold runs can prevent them from creeping up above their true lactate threshold pace.
For Hybrid Athletes
A hybrid athlete is someone who trains for both strength and endurance. Some hybrid athletes train exclusively for those two—such as powerlifting and marathon running—while others also include other elements of fitness, like calisthenics and plyometrics. Examples of hybrid fitness include CrossFit and Hyrox racing.
[Read More: How to Run a Faster Mile, According to a Running Coach]
For these types of athletes, performing at least one threshold run per week is ideal, says Rodgers. However, hybrid athletes can include more threshold training in their weekly programming by including threshold pace runs with other training elements, he adds.
For Endurance Athletes
Threshold runs are extremely important for endurance athletes. Baldwin says endurance athletes, particularly those following a workout program for a specific upcoming event, should be engaging in threshold interval training at least two times per week.
“It’s a stimulus we want to touch on often,” he says. An exception to this is athletes who need to focus on improving their aerobic base, in which case they can benefit from sticking to lower-intensity work for a training block.
At the end of the training block, the athlete would retest and recalculate their threshold pace. They’d then use the new, faster pace, beginning with three 1-kilometer reps.
Benefits of Threshold Runs
Training at anaerobic threshold paces comes with big benefits for your fitness and performance. The key purpose of a threshold run is to improve your lactate threshold, Rodgers says.
“This, in turn, helps you to run at faster paces without experiencing excessive lactate buildup in your body,” he explains. “Lactate is produced when you exercise at high intensity, eventually slowing you down. The lactate threshold is the point at which your body starts to produce more lactate than it can clear.”
By running at or just under your lactate threshold, you can gradually increase it and run at faster paces before reaching it. The result: run faster for longer.
Takeaways
- There are two main thresholds used in running training: aerobic and anaerobic.
- At the aerobic threshold, your body runs on fats via oxygen metabolism but is close to tipping over into anaerobic metabolism.
- At the anaerobic threshold, blood lactate accumulates faster than your body can get rid of it.
- Your body starts prioritizing carbohydrate stores as fuel at anaerobic threshold paces.
- Anaerobic threshold is a significant performance indicator.
- Your anaerobic threshold pace is what you can sustain before experiencing significant fatigue accumulation.
- Lactate threshold occurs at about 80 to 90 percent of your HRmax.
- Performing at least one threshold training session per week is recommended by most running coaches.
- Threshold training helps you run faster for longer, i.e. improves your endurance.
Frequently Asked Questions
How do you calculate running threshold?
The best way to calculate your running threshold is to undergo various physiological tests at a sport science lab. In such a setting, you’d run on a treadmill while sport scientists measure factors like oxygen consumption, breathing patterns, heart rate, and blood lactate levels. This will provide you with the most accurate picture of your current baseline performance.
You can estimate your threshold pace by using your functional threshold pace (the maximum effort you can run at for 60 minutes) or by using your heart rate (running at about 80 to 90 percent of your maximum heart rate).
How long should threshold intervals be?
Threshold intervals can be programmed in distance or in time. They can be as short as one mile or extend for several miles, depending on the percentage of threshold you’re working at and the length of the recovery interval.
For instance, your plan may call for a six-mile run at tempo pace (five to 10 percent below threshold) or four sets of one-mile runs at 105 to 110 percent of threshold effort. Or, your plan may say something like: 10-minute zone 2 warmup, 20-minute run at threshold pace, and a 10-minute cooldown in zone 1-2.
What is the heart rate zone for the threshold run?
Lactate threshold occurs at about 80 to 90 percent of the athlete’s maximum heart rate. Well-trained runners can typically run at higher percentages for longer.
How often should I incorporate threshold runs into my training schedule?
Most coaches program threshold running at least once per week, but often more, depending on experience level and current fitness. “An elite athlete may complete four threshold-based workouts in a week, often using the threshold interval approach,” Rodgers says.
“Double-threshold days have become increasingly popular for elite-level athletes due to the recent success of high-profile athletes using this method. However, remember that they are often world-class athletes and have built this volume up over time.”
A beginner, he says, will still benefit from a threshold-based workout once a week or every ten days.
References
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