Of the many types of running workouts, threshold workouts can be the most versatile – and yet most confusing. (This confusion is due to “tempo” runs sometimes being used to describe threshold, but sometimes not.) When used correctly in training, threshold workouts are an incredibly beneficial performance booster for long-distance runners. This article will delve into the rationale behind them and how to use the various forms of threshold workouts in your training.
What Are Threshold Workouts?
While not all tempo runs are threshold workouts, threshold workouts are a sub-type of tempo run. (They can also be structured as intervals, which we will delve into more here).
Threshold workouts are done right around your lactate threshold. For most runners, their lactate threshold is roughly the pace that they could run if they were racing for an hour (hour-race pace). There’s not a set race pace equivalent. For some runners, threshold pace falls close to their 10K pace; for elites, threshold pace is roughly half marathon pace. These deliberately paced sessions will feel moderate/moderately hard. They train your body to shuttle lactate more efficiently and delay the accumulation of hydrogen ions, thus effectively raising your lactate threshold. The higher this threshold, the longer you can work within aerobic capacity even when running relatively hard. You are able to delay lactate accumulation, which means fatigue is delayed. You also raise your aerobic threshold (first ventilatory threshold).
Why Train at Lactate Threshold?
Your lactate threshold is the point at which lactate accumulates in your blood past the point that your body can shuttle it and recycle it as energy. This is the same as your second ventilatory threshold (when RPE crosses from moderate to hard and breathing is substantially more labored). It is also the same as your anaerobic threshold, when your body crosses from aerobic energy production to a combination of aerobic and anaerobic. If we look back at the common training intensity zones, the lactate threshold falls right at the top of Zone 2.
Lactate itself is not the problem; we only refer to lactate because it can be easily tracked using blood measurements. The real problem are the by-products of lactate metabolism, including hydrogen ions. These alter the pH of the muscle. When the muscle pH is altered, your neurons send signals that the brain perceives as pain – that burning sensation in the muscle. Additionally, the pH imbalance inhibits muscle contraction, which means you simply cannot produce as much power, i.e. you slow down.
While VO2max does not respond significantly to training, you can raise your lactate threshold significantly. Additionally, while performance may not always correlate to VO2max, it does with lactate threshold; when your threshold improves, your performance improves.
I would argue that additionally, threshold workouts also prepare athletes for the specific neuromuscular demands of racing anything from the 5K to 50K. All those events require sustaining a moderate to hard effort for a prolonged period of time. In addition to clearly lactate, your body has to tolerate that degree of mechanical loading. Your brain has to stay sharp and clearly communicate with your muscles.
The Training Theory of Threshold Workouts
If you peek into the training of the current best of the best, including Olympic bronze medalist Molly Seidel and Olympic record holder Jakob Ingrebrigsten, threshold workouts are a staple throughout their race-specific training. (Both will do faster, shorter intervals in pre-competition seasons.) Both these athletes rely heavily on threshold intervals, often completing two threshold workouts in one day. (Remember: these are world-class athletes; double quality session days are not advised for recreational and low-level competitive runners.) This is despite the fact that Seidel’s discipline is the marathon and Ingrebrigsten’s is the 1500m.
The driving principle behind a 1500m runner and a marathoner using similar workouts is the aerobic contribution for both of those distances. Both the 1500m (approximately a 3-4 minute race) and the marathon (2-2.5 hours) are predominantly aerobic. The marathon is almost entirely aerobic. Meanwhile, the 1500m is 70-85% aerobic depending on the athlete (according to a 2021 study in Sports Medicine).
Notably, marathoners will gravitate towards longer threshold repeats (1-mile, 2K, 2-mile). Track athletes may do them slightly faster for shorter durations (1K). However, you will generally find a mix of both shorter threshold intervals, longer threshold intervals, and continuous threshold runs in these runner’s training.
Threshold workouts are often a highlight in particular training intensity distributions. While polarized training prefers high-intensity intervals, pyramidal training and threshold distributions rely more on bigger volume of threshold training in the context of higher mileage. For many athletes, focusing on mileage and threshold work produces less fatigue and lowers injury risk compared to very fast workouts on the track.
How to Pace Threshold Running Workouts
I have said again and again that faster workouts are not better workouts. This adage is particularly true in threshold workouts. It can be tempting to push threshold intervals a little harder or to race a tempo run. However, doing so can cause lactate to accumulate too quickly and cause you to fatigue too soon. Running too hard will miss part of the purpose of the workout.
Elite runners take pacing threshold workouts very seriously. Some even use blood lactate monitors during the workouts to ensure they are working at the appropriate intensity.
Controlled pacing is key in threshold workouts. These workouts fall into the “moderate” category on the intensity spectrum and will feel moderate to moderately hard during. You want to genuinely feel as if you could maintain that intensity for an hour if you were racing. You can use RPE to assess the effort, pace (if using a recent race or threshold test), or heart rate. If in doubt, it’s better to go a bit slower than too hard.
Sample Threshold Running Workouts
Threshold workouts can be continuous or broken into intervals. Continuous threshold workouts range from 15 to 30 minutes at hour-race effort. Threshold intervals are effective to run a higher volume or to minimize fatigue. You can break the intervals into 3 to 15 minute increments, with short rest (1-2 min) in between. Threshold intervals are under-utilized in many recreational runner training plan. However, doing 1-K, 1-mile, and 2-K repeats at threshold pace can provide a fun and highly effective workout.
Sample workouts include:
- Introductory/Early Season: 4-6 x 5 min at threshold, with 1-min recovery jog in between
- Anytime: 4-6 x 1 mile at threshold with 1-min jog in between
- Continuous: 20 minutes at threshold effort
- Advance/Peak Weeks: 3-5 x 2K at threshold, with 2-min recovery jog
With any of these workouts, include a 10-20 minutes warm-up and cool down.
Be wary of any threshold workout that totals more than one hour’s worth of running. So, for example, if you run a 10K in one hour (and therefore your 10K pace is your threshold run pace), do not do an 8 mile threshold workout. That’s not a workout; that’s a race at best and a quick way to overtrain at worst.
How to Use Threshold Workouts to Your Training
- Periodize your training for a threshold phase: Whether or not you are immediately training for a race, periodizing training into different phases is beneficial. A four to eight week phase focused on increasing lactate threshold can be highly beneficial. Plus, it offers welcome change from interval workouts.
- Use threshold workouts closest to physiologically similar events: Varying through different types of workouts builds all aspects of fitness. However, it does not make sense to do both of these workouts every week. When training for a race, the most beneficial workouts are those that work the most specific systems are closest to the race demands. A half marathon and marathon both rely on having a high lactate threshold. You can use threshold workouts in the peak weeks of training for those races.
- Advanced runners can try two threshold workouts per week in certain phases: Double threshold days are reserved for world class runners. However, the principle can be applied to a weekly training cycle. In some cases, doing two threshold-range workouts per week can provide a beneficial stimulus for the half marathon or marathon. A sample structure is seen in this post, which demonstrates a training week with 1-mile repeats at 10K pace (just above threshold) and 2-mile repeats at half marathon pace (just below threshold).