Aerobic threshold training is not high on the agenda of most endurance runners. Instead, we obsess about maximal aerobic capacity (VO2 max) and the lactate threshold. Tangible signs on our smartwatch that fitness is improving.
“A high aerobic threshold is a sign of a solid aerobic base.”
But without a high aerobic threshold, improvements in our VO2max and LT will invariably stagnate after 6 – 12 weeks. In other words, look below the tip of the iceberg for large, continuous improvements in your race performance from the 5K to the marathon.
What Is The Aerobic Threshold
The aerobic threshold (AT) is the intensity at the upper end of zone 2 training. AT runs are also called steady-state runs or high-end aerobic runs. They are faster than your day-to-day easy runs but slower than tempo runs. In my training plans, I refer to them as moderate pace.
There is a lot of talk about polarized training (targeting paces at the extremes of the intensity spectrum) where anything between easy pace and lactate threshold pace is pushed aside as being in the zone of “no man’s land”. And while I do agree that training should generally be polarized, I advocate using the full spectrum of training intensities.
My training plans are sprinkled with moderate pace, marathon pace, 30K pace, or HM pace once a week – or at least a segment thereof during an easy run or at the end of a long run. Depending on your training level, these paces are somewhat below, at, or slightly above your aerobic threshold.
Aerobic Threshold vs Lactate Threshold
The lactate threshold needs no introduction. It is one of the 3 performance markers for distance running performance, alongside VO2 max and running economy. Therefore, the lactate threshold is featured on most GPS smartwatches and can be the reference point for setting up training zones. But the aerobic threshold is often overlooked, let alone understood.
The aerobic threshold occurs when lactate rises above the baseline of 2mmol/L. This is your LT1, ventilatory threshold 1, or roughly your 3-hour race pace. Hence, marathon pace for advanced runners or slightly faster than marathon pace for intermediate runners. It sits between 65 – 75 percent of VO2 max for amateur runners, assuming you’re not a beginner.
The lactate threshold is the point above which you produce lactate faster than you can clear it. This is your LT2, ventilatory threshold 2, lactate turnpoint, maximal lactate steady-state (MaxLass or MLSS), and onset of blood lactate accumulation (OBLA). This corresponds to a one-hour race pace and thus roughly 15K pace for advanced runners or between 15K and 10K pace for intermediate runners, or 80 – 90 percent of VO2max, depending on your training level.
The aerobic threshold and lactate threshold are linked. A higher aerobic threshold will push your lactate threshold to some degree, and a higher lactate threshold will drag the aerobic threshold upwards. But not entirely so. As a result of your training, the gap between the 2 thresholds can be rather wide or narrow. And this—as you will soon discover—has significant implications for your training and race performance.
The Downside of a Low Aerobic Base
It is possible to be a strong athlete with a high VO2 max yet suffer from a lack of aerobic fitness. The scientific term for this is Aerobic Deficiency Syndrome (ADS). I was one of these guys. In my late 30s I could run a 400m in 54 seconds, the 10K still around 36 minutes, and yet, I would struggle to go past 1:24 hours in the half marathon. (That’s a sharp downward performance slope for anyone who knows about equivalent race times.) Not to mention that long runs were a chore, and on intervals, I’d run out of gas on the 4th or 5th repetition despite having the lungs and legs for it.
My well-intended experiment with low mileage (4 runs and 25 miles/week) wasn’t enough to support the key workouts at that level. I would suffer more in hard workouts than necessary, needed more time to recover, and couldn’t progress the training appropriately. I had neglected my aerobic base. In other words, my aerobic threshold was underdeveloped. Hence, the efficiency of my fat metabolism and glycogen storage capacity were sub-par, sabotaging training and race performances.
Things started to change for the better when I reduced the pace of my easy runs but increased the duration for all easy runs. I also sandwiched harder sessions with a longer warm-up and cool-down and added an easy run the day after my long run. Consequently, I could run a faster aerobic pace at the same heart rate, which is a sign of an increased aerobic threshold.
How to Calculate Aerobic Threshold
You get the most accurate results by testing your lactate levels with a portable lactate analyzer in a controlled environment (e.g., on a treadmill). That’s how professionals do it. It will set you back around 500 USD, but if you have the money to spare, it might be a good investment to monitor your training progress every few weeks.
Another method is the breath test. Observe your heart rate and find the maximal point where you can still breathe through your nose with your mouth closed. This should align with the uppermost limit, where you can still speak in complete sentences without gasping for air.
You can also have an educated guess via your heart rate reserve, which you can calculate with the Karvonen method based on your resting and maximal heart rates. Your aerobic threshold falls between 65 and 75 percent of VO2 max for most intermediate and advanced runners.
Finally, you can use the MAF test developed by cardiologist Phil Maffetone. Here, you subtract your age from 180 to determine your aerobic threshold heart rate. If you suffer from health problems, subtract 10 bpm, and if you consider yourself in perfect health, add 5 bpm.
How to Improve Your Aerobic Threshold
For the most profound impact on your aerobic threshold, I recommend that you increase your weekly mileage for zone 2 training. You can do this with an additional running day, adding mileage to your midweek easy run or weekend long run, or lengthening the warm-up and cool-down on key workouts. All of this within reason, of course. Note that zone 1 running, while great for recovery, won’t be enough to significantly impact your aerobic threshold.
You can include a high-end aerobic run (~marathon pace) into your running week. Consider also running above the aerobic threshold occasionally with 30K – HM pace which is still well below your lactate threshold unless you run the half-marathon in 1:20 h or faster. Those can be add-ons to long runs for runners preparing for half marathons and marathons.
Speed training, VO2 max intervals, and lactate threshold runs will, of course, have a downstream effect on your aerobic threshold. The problem is that these workouts require significantly more time to recover than runs around the aerobic threshold or below. For that reason, gradually increase your mileage first before you extend your work at higher intensities.
Aerobic Threshold Workouts
Here are 3 aerobic threshold workout formats, one of which you could include in your training week:
Intermediate: 5 miles @moderate pace (30K pace)
Advanced: 8 miles @moderate pace (30K pace)
Alternations
Intermediate: 3x (1 mile @HM pace + 1 mile easy )
Advanced: 3x (2 miles @HM pace + 1 mile easy)
Progression
Intermediate: 3 miles easy + 2 miles @marathon pace + 1 mile @HM pace
Advanced: 4 miles easy + 3 miles @marathon pace + 2 miles @HM pace
Periodization
Improving your aerobic threshold is not a last-minute quick fix a few weeks before your key race. Your aerobic threshold is the foundation for all workouts you intend to complete in a training cycle. Without a solid aerobic base, you will fall short of your potential in VO2 max and lactate threshold workouts – essential for a strong race performance.
For this reason, develop your aerobic base with sufficient zone 2 training and complement it with high-end aerobic workouts early in your training cycle. Then, piggyback the finer points of training adaptations on this solid foundation, where you can manage harder training sessions with a reduced risk of overtraining and injury.
Compared to workouts at higher intensities, it may take more time to see performance gains with aerobic threshold training. However, consistent work at the lower end of the performance pyramid takes you to a higher level over the long term.
