No matter what your goals are—you should be doing threshold intervals. Spending time close to your functional threshold power (FTP) offers extraordinary benefits to your aerobic capacity, muscular endurance, mental stamina, and sustained power capabilities. Not to mention, doing threshold intervals will help to increase your FTP!

What is Threshold? (FTP) 

In cycling training, the term threshold refers to your functional threshold power (FTP). Your FTP is an estimate of the highest amount of power you can sustain for sixty minutes. This metric helps scale your workouts to your current fitness by defining your power zones for power-based training. Fortunately, you won’t have to complete an all-out sixty-minute effort to determine your FTP. You can get an accurate estimate of your functional threshold power with an FTP assessment like the Ramp Test. Once you’ve evaluated your FTP, you’ll also know your threshold power zone. The threshold power zone is defined as the power between 95% and 105% of your FTP. Riding at this percentage offers benefits to your aerobic capacity by growing your ability to sustain efforts near your FTP.

Threshold Training 

While threshold is theoretically the power you can sustain for an hour, in practice, most athletes find that riding at their FTP for more than twenty or thirty minutes, isn’t a sustainable or a repeatable effort—that is until they’ve done a bit of threshold training. Threshold training includes intervals and workouts that target your ability to ride at your maximum steady-state power. Athletes can improve their threshold capabilities with a structured training plan or a threshold training progression.

Of the two, a structured training plan is the most sustainable way to grow your threshold capabilities. Training plans have a built-in progression, that ensures that the threshold workouts gradually increase in challenge, duration, and specificity. Training plans also integrate recovery weeks and rest days into the plan to guarantee that you have enough time to recover and adapt from hard workouts. Finally, training plans include a diverse range of structured workouts to build more robust and well-rounded capabilities. For example, most training plans include Sweet Spot workouts alongside threshold workouts, which are another effective way to train your threshold power.

Adaptive Training

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Check Out TrainerRoad

You don’t have to commit to a structured training plan to reap the benefits of threshold training, though. You can create your own threshold progression on the fly with TrainNow. TrainNow uses your performance in completed TrainerRoad workouts to suggest workouts geared towards your current level of fitness. Using this tool, you can select threshold workouts at your own rate that are still geared towards your abilities. If you have experience designing your own training plans, you can also build your own threshold progression using the workouts from the TrainerRoad workout library. The TrainerRoad library has over three thousand workouts to choose from and filters to help you find the exact workout you’re looking for. Either way, you’ll be cashing in on the many benefits of threshold intervals.

Benefits of Threshold Intervals 

Threshold intervals are aerobic efforts that challenge some of your anaerobic capabilities. Riding at this level of intensity helps expand your aerobic capacity for greater endurance at high intensity and helps grow some of your anaerobic capabilities. Threshold intervals also activate a large volume of type IIa muscle fibers—placing significant emphasis on your muscular endurance. Riding in this zone increases blood plasma volume and mitochondrial enzymes while improving the ability to maintain high intensities for long periods. Threshold intervals are typically accompanied by significant fatigue and discomfort, offering countless opportunities for you to grow your mental stamina. 

Repeatedly spending time riding near your threshold increases your capacity to ride at this level of intensity. The more you do threshold intervals, the longer you’ll be able to hold your threshold power. Eventually, these adaptations and your ability to sustain these power will surpass your current threshold. At this point, your FTP will have increased, and it will be time to reassess your FTP with another Ramp Test.

Example Threshold Workouts 

Threshold workouts come in many shapes and sizes. In the TrainerRoad library alone, there are 972 Threshold workouts and ten types of interval structures. Here are a few example threshold workouts, their structures, and the benefits they offer cyclists.

Threshold Intervals With Hard Starts

Sustained power intervals with hard starts target your ability to maintain a high intensity over a sustained period while fighting muscular fatigue onset by VO2 max intervals. The primary objective is to learn how to recruit a lot of muscle quickly for a powerful and effective sprint but then cut the effort down to a manageable but difficult level that you can sustain for an extended duration.

This is Owl +2, a sustained threshold workout that's 1 and a half hours long and contains five intervals. It shows high power start at the beginning of every interval.
The Owl +2 is a sustained threshold workout with hard starts.

The Owl +2 is an example of a threshold workout with hard starts. This ninety-minute threshold workout includes five nine-minute intervals, each with a 30-second wind-up at 140% FTP. These hard starts are followed closely by 8 minutes of Threshold work at 95% FTP and five minutes of recovery in between, making for a challenging but efficient way to improve your threshold abilities.

Over-Under’s

Over-unders are workouts with intervals that alternate between supra-threshold and sub-threshold. The objective of over-unders is to increase your ability to tolerate and utilize the byproducts that accompany riding above your FTP, all while maintaining reasonably high power output. These intervals can increase how long you can work above FTP and how quickly you can reprocess the lactate buildup that can lead to muscle acidity. The short efforts above your current FTP can also lead to increases in FTP.

This is a threshold interval workout Starlight -2. The graph shows three over-under intervals.
Starlight -2 is a threshold workout with over-under intervals.

Starlight -2 is an over-under threshold workout with three sets, each with four minutes at suprathreshold and six minutes at sub-threshold. You can find starlight -2 in the TrainerRoad workouts library as well as the Low Volume and Mid Volume sweet spot base plans. 

Mixed Intervals

Another variety of threshold intervals you’ll come across in the TrainerRoad library are mixed intervals. Mixed intervals are workouts with intervals from other power zones dispersed between the threshold intervals. In these workouts, the threshold work aims to improve muscular endurance, the VO2max efforts target aerobic capacity, and the anaerobic repeats fall somewhere in between.

Robion is a threshold interval workout that is 1.5 hours long. The graph shows four sets of mixed intervals all at or above threshold.
Robion is a threshold workout that touches on anaerobic capacity and VO2 max work.

Robion is a good example of a threshold workout with a mix of intervals. The majority of the intervals in Robion are spent in the Threshold power zone, with one interval in the anaerobic power zone and one in the VO2 max zone. Mish-mash intervals like these address several performance attributes within the confines of a single set of efforts.

Threshold Workouts in a Training Plan 

In a training plan, you’ll find these example workouts and more integrated into the weeks of your program. Structured training plans include workouts that progressively increase the challenge duration and specificity of your intervals so that your abilities can progress in time with your training. Essentially you’ll find more moderate threshold workouts with longer intervals of rest at the beginning of the first training phase, like a sweet spot base phase. In the build phase and the specialty phase, you’ll have more challenging workouts geared more specifically towards the type of threshold capabilities you need.

Tips for Successful Threshold Intervals

There’s no doubt about it—riding close to your functional threshold power is uncomfortable. Fortunately, training isn’t the only way to improve your ability to ride at the threshold.  You can lower the rate of perceived exertion of your threshold workouts when you follow these steps. 

Fuel Your Workouts

Threshold intervals are highly glycolytic efforts that shift fuel demands from fat to sugar. Fueling, before, during, and after with carbohydrates ensures that you have enough fuel on board to power through all of your threshold efforts. Going in fueled can also decrease the rate of perceived exertion. To ensure that you have this advantage, eat a carb-rich meal two to three hours before your workout. During the ride, plan on taking in 60-120g of carbs per hour to stay on top of your system’s demand for fuel.

Further Reading on Carbohydrates

Ride With a Fan 

If you’re doing threshold intervals indoors, you’ll want to ride with a fan. Riding indoors provides significantly less airflow than riding outdoors, which negatively affects your body’s ability to cool itself. The impact grows considerably more challenging as you progress into more intense intervals. Riding with a fan during threshold intervals can help reduce the RPE of your workout and increase your efficiency indoors.

Rest and Recover

Threshold intervals are intense enough that you won’t want to do them back to back. Similarly, it’s essential to maximize the recovery that you get in between your threhsold workouts. If you’re following a structured training plan, your plan will automatically integrate an appropriate amount of rest in between your threshold workouts. However, if you’re selecting workouts from the workout library or using TrainNow to pick workouts, you’ll need to integrate rest in between workouts. For more information on how to maximize rest and recovery, you can check out our complete guide: The Complete Recovery Guide.

Test Your FTP Regularly

Nothing makes a threshold workout less productive than an outdated FTP. If your FTP is too high, the easiest threshold workouts may be too challenging. If your FTP is too low, your threshold workouts might actually be sweet spot workouts. You can keep your FTP accurate with a functional threshold power test every six weeks. Similarly, if you take time off of training or miss weeks of training unintentionally, it’s a good idea to reassess your FTP when you return. Remember that your functional threshold power isn’t a value of your fitness as much as it is a tool to keep your training accurate.