Unlock Your Athletic Potential:The Complete Guide to Threshold Training

Table of Contents

Introduction

Whether you're an aspiring athlete, a weekend warrior, or a dedicated endurance enthusiast, improving your performance requires more than just hard work; it demands smart, targeted training. While traditional workout plans often focus on generic heart rate zones, the science is clear in that a more precise and effective method exists: threshold-based training.

This guide is designed to help you understand the key physiological thresholds that govern your body’s ability to produce energy and how you can leverage that knowledge to train smarter and achieve better results. It will not propose any new frameworks, simply explain how directly measuring your physiological limits can slot nicely in with the 5-zone training model.

Below, you will discover:

  • The science behind energy production and why understanding your fat and carbohydrate utilization is key to sustained performance.
  • How understanding your individual thresholds, VT1, Balance Point, VT2, and VO2max, can dramatically improve your results.
  • Why training based on metabolic thresholds consistently outperforms traditional heart rate zones.
  • A clear path to building a balanced metabolic profile, ensuring continuous improvement without plateaus.

This guide simplifies complex sports science into actionable insights you can apply directly to your training. Whether you’re looking to break new records, improve your endurance, or simply train more effectively, the strategies in this guide will help you make every workout count.

Get ready to unlock your full potential and take your training to the next level.

Chapter 1: The Science of Performance

Your athletic performance depends on how efficiently your body converts oxygen into energy. At low intensities, your body primarily uses fat as fuel, which is difficult to break down but yields over twice the energy per gram as carbohydrates. As intensity increases, your body gradually shifts to using carbohydrates as its main energy source due to their faster energy release. These shifts occur in phases, and your body signals when it’s shifting phases through physiological processes called thresholds.

These thresholds can be observed through ventilation and measuring blood lactate levels. Ventilation is the gold standard and has been used in metabolic labs all over the world for decades. Measuring blood lactate levels is another way athletes and scientists have tried to take the insights that ventilation provides out of the lab and into the field.

Measuring these thresholds has never been more accessible, and to improve performance, athletes must train to efficiently utilize both energy sources. The key to this is understanding your physiological thresholds.

Chapter 2: Understanding Your Thresholds

Your body has 3 thresholds along with VO2max that determine how efficiently it can produce work. These thresholds are what really divide your training zones and in application the thresholds themselves are much more effective as training targets than the zones in between them. This is where substrate utilization comes into play in a big way and we’ll explain it in the simplest, most actionable way possible.


Your energy production is powered by two main sources, fats and carbohydrates. Fats are hard and slow to break down but provide a lot of energy per molecule. Carbs provide less energy but much faster so as your intensity and need for energy increases you need to shift to utilizing more carbohydrates. Below you can see how the substrate utilization lines up with the ventilation signal with respect to the ventilatory thresholds during a ramp threshold test where the speed or power increases by the same amount every 2 or 3 minutes.

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VT1 - Aerobic Threshold, Top of Zone 2

  • Feels like light intensity
  • Improves mitochondrial growth, fat utilization, and oxygen uptake
  • Key to sustaining long-term endurance

You’re likely familiar with zone 2 training at this point given its marketing team. That’s a good thing as zone 2 training is incredibly important to improve aerobic capacity and get you acclimated to utilizing the fat stores in your muscles as energy. Training in zone 2, below your VT1, can feel almost too easy and is often referenced as 3/10 on the rate of perceived effort scale (RPE), but that’s a good thing. Wouldn’t you want the most helpful tool in your training toolkit to be easy?

As a threshold commonly known as FatMax, you might think it’s one point where fat utilization reaches its maximum level and we’re able to pick it out of our dataset. This isn’t exactly the case since FatMax is usually reached before VT1 and maintained. So if there’s no change in fat utilization and we’re not detecting the max point what is VT1?

VT1 is detected as a small uptick in carbohydrate utilization while increasing intensity. Before VT1 you are in a steady state where fat utilization can largely provide the energy needed at that intensity level. As you increase the intensity past VT1 your body needs to start supplementing with more carbohydrates, increasing the volume of CO2 in your body which you need to exhale causing the inflection point we detect as VT1.

Balance Point - Tempo, Sweet Spot, Top of Zone 3

  • Feels like moderate intensity
  • Expands fat burning capabilities
  • Helps sustain higher power output at light effort levels

VT1 is commonly known as FatMax as it’s the point at which you are utilizing the maximum amount of your intramuscular fat stores. The balance point is a less known entity but in a lot of cases it’s even more important than VT1. 

Your balance point is the point at which your fat utilization starts to drop with increased intensity.

What does that mean?
Well despite VT1 being labeled as FatMax that doesn’t mean it’s the only place you can burn the maximum amount of fat. In fact most athletes can maintain their FatMax quite long after the VT1, all the way up to the balance point. This is where the nickname “The Sweet Spot” feels very pertinent as it’s the highest intensity you can hold before your fat utilization drops off and you start to really feel the effort, or as people in the industry would describe it: RPE shoots up.

VT2 - Anaerobic Threshold, Race Pace, Top of Zone 4

  • Feels like hard intensity
  • Boosts race performance, muscle strength, and calorie burn
  • Critical for high-intensity efforts

VT2 is commonly known as the anaerobic threshold or just threshold. It’s the point at which your body can no longer recycle the lactate and hydrogen ions that are generated as byproducts of glycolysis (turning carbohydrates into energy). Up until VT2 the lactate is turned into more energy at a fast enough rate that it doesn’t start to build up in your muscles. After VT2, lactate and the H+ ions can no longer be recycled fast enough which will eventually make your muscles “sour” and prevent them from contracting. This feeling is often associated with “lactic acid”.

VO2max - Maximal Aerobic Capacity

  • Feels like very hard intensity
  • Stimulates mitochondrial growth and improves oxygen utilization
  • Sets your overall aerobic ceiling

VO2max is your maximal aerobic capacity or the maximum amount of oxygen your body can utilize for energy production during exercise. It’s currently the main way people use to quantify fitness level and does that quite well. Who knows, maybe in a few years people will compare their VT1 or balance point values instead of VO2max.

Chapter 3: Why Train with Threshold-Based Zones?

Now you know about the thresholds and the underlying processes that cause them but why are they so important?

Research has shown time and time again that training based on personalized metabolic thresholds produces better results than generic heart rate zones. A 12-week randomized control trial found that athletes using metabolic thresholds to guide their intensity in training improved their VO2max by 11.7%, compared to just 4.9% in those following traditional heart rate zones. Even more damning than that, 7 out of the 12 participants that used the heart rate reserve formula to set their intensity didn’t improve despite consistent training for 12-weeks. Imagine not improving at all over 12-weeks of training hard, following a program and using training zones that you think are personalized to you. This is much more common than people realize. To contrast this, in the metabolic threshold group, all 12 participants improved and as we mentioned before, they improved by 11.7% on average over just 12 weeks.

This study tells us what coaches and professional athletes have known for years and have used in their training. In that world everything is based on the knowledge they can measure so they can make informed decisions about the needed intensity for each session, when to rest, and when to push on. It hasn’t always been easy to get these insights for your average athlete but as technology advances more and more people gain access to the information that really matters.

Chapter 4: Identifying Your Strengths and Weaknesses

Yes, knowing where your thresholds lie is an incredible tool to improve your training and professional athletes make sure to measure them regularly. But those professional athletes also have professional coaches that make sure to target the correct thresholds at the right time in their training cycle. Having a coach tell you where to train and for how long is obviously a great help to anyone trying to improve their endurance, but if you’d like to do it yourself, how do you know where to start?

Athletes should tailor their training based on their unique metabolic profile. A metabolic profile is what we call the results from a threshold test. It maps out how you respond across the intensity spectrum. Recall the Fat, Carbohydrates, and Minute Ventilation chart above, that is a metabolic profile. It contains your thresholds which make up your training zones. But, even more helpful, and the final step in utilizing your thresholds, it shows you which threshold is limiting your overall improvement and in doing so, which threshold you can improve the fastest. 

For example:

  • An athlete with a strong Balance Point and VT2 but weak VT1 will be held back at higher intensities by their lack of ability to utilize fats for fuel. This athlete should focus on Zone 2 training, at and below VT1, to first improve their aerobic base before continuing to push their other thresholds higher.
  • Conversely, an athlete that has been building their aerobic base diligently and has a strong VT1 may see their performance plateau. This is likely because their VT1 improvement is now being stunted by their Balance Point and they need to focus on that before building their aerobic base further.
  • Finally, an athlete that varies their training between their thresholds but never pushes themselves quite hard enough to get to VO2max will absolutely improve but unless they raise their ceiling (VO2max) directly it will feel like trying to add a new floor to your home without first raising the roof.

As you can see by these examples there’s no one perfect training philosophy. Each of us are different and need to focus on different parts of our endurance. Like in so many other fields, knowledge becomes the key to continued success and development so let’s take a look at how to best balance your thresholds for that continued success.

Chapter 5: Creating a Balanced Profile

A balanced metabolic profile across most endurance sports looks something like this:

  • VT1: 60%-65% of VO2max
  • Balance Point: 70%-75% of VO2max
  • VT2: 80%-85% of VO2max

If one of your thresholds is below these ranges that means it could be limiting your overall performance and, on a positive note, it’s primed and ready to improve faster than the rest of your thresholds. We recommend testing every 4-8 weeks which gives you enough time to focus on and improve your limiting thresholds before resetting your targets. Once you get all your thresholds within these balanced ranges you are ready to raise your VO2max further.

This process of first improving your thresholds to be in a balanced range and then pushing your VO2max high enough that your thresholds fall out of range again makes sure you’re always progressing, always improving based on your fitness level. Building your fitness is like building a skyscraper: you can’t add floors until the foundation is strong enough. Thresholds are the structural base. VO₂max is the skyline you’re reaching for. And once you go higher, you’ve got to reinforce and expand the base again to support the new height.

Chapter 6: Personalized Training Strategies

Let's take another step into the details of the metabolic profile and how to effectively target weaknesses. Once you have your metabolic profile in hand it’s important to know how to structure your training around the focus of this training block. The easiest way to explain this is with two real world examples. 

1. Imagine an athlete that has both VT1 and Balance Point below the balanced range but VT2 is within or above the balanced range. For the next training block they should focus on improving those areas while adding in 1 high intensity workout every 7-10 days that targets their VO2max to maintain it. 


Here’s a training split that would make sense for this athlete:

  • Spend about 60% of their training time in Zone 2 to improve their VT1
  • Spend about 35% of their training time in Zone 3 to improve their Balance Point
  • Spend about 5% of their training time in Zone 5 to maintain their VO2max

2. Now imagine the same athlete has a perfectly balanced profile after 6 weeks of the training described above. Now they are primed to improve their VO2max to make room for further improvement to their thresholds.

Here’s what their training splits should look like:

  • Spend about 70% of their training time in Zone 2 to improve their VT1
  • Spend about 15% of their training time in Zone 3 to maintain their Balance Point
  • Spend about 15% of their training time in Zone 5 to improve their VO2max

Chapter 7: Practical Application in Training

Now, despite having the proper training volume in each zone you’re still missing the answer to the real question at hand. Coach, what should I do today?

A real training plan provides specific workouts every single day so why should we do anything different? I, a semi-active retired athlete, should not do the same training as a professional cyclist on the Tour de France. Luckily, how much each of us needs to train to maintain or improve our fitness can be derived from our VO2max which means that the total weekly Kcals needed to maintain your fitness level can be calculated from your threshold test results. 

So, since the personalized training zone splits are represented as a ratio of total training we can apply that ratio to the total weekly kcals you should expend on training per week and get the exact amount of training needed in each zone for you to keep improving. Then it’s just a matter of selecting the proper workouts that sum up to your total training while making sure to save enough room for rest days.

Here are common examples of workouts for each training zone:

Zone 1. Rest Day. Since there’s not a clear way to distinguish between zone 1 and zone 2 (although we have some ideas) the easiest way to describe zone 1 is by labeling it as a rest day.


Zone 2. Long, slow, steady state workouts at and below your VT1. The key here is to stay at or below VT1 and make sure you’re ready to go again tomorrow!

Zone 3. Balance Point workouts are designed to extend fat utilization into the intensity spectrum. Here you want to target balance point by using either the Heart Rate or Minute Ventilation target as a ceiling, making sure you stay below Balance Point. Common Balance Point workouts are 6-10 minute intervals after a good warmup.

Zone 4. VT2 “threshold” workouts are common and mainly help with sharpening up before a race. The most common threshold workouts are intervals that can range from 3-8 minutes but another fun one is called the Lactate Clearing workout. Here you want to do 1-4 minutes just above VT2 and then a few minutes below VT2 but still in zone 4. This aims to get your body used to clearing the built up lactate at a reasonably high intensity.

Zone 5. VO2max workouts are definitely fast but not quite sprints. Intervals can range from 20 seconds up to 4 minutes for advanced athletes. Common workouts include 4x4 minute intervals and 30x30 second intervals with at least equal rest in between.

Chapter 8: Measuring Progress

Earlier in this book it was mentioned that measuring thresholds has never been more accessible. One of the biggest advantages of this accessibility is being able to test often to measure improvements and adapt training plans based on those improvements. As I’m sure you can imagine, it’s frustrating to spend heaps of money going to a metabolic lab if the results you get will be outdated within a couple of months. 

What should you look out for when quantifying your improvements?

Power or Speed at your thresholds. For the clearest sign of improvement look for the intensity you’re able to maintain as you cross each threshold.

Ventilation at your thresholds. Testing for your thresholds is first and foremost to establish your training targets so make sure to make note of your new breathing targets.

Chapter 9: Get Started with Tymewear

This ebook wouldn’t be complete without offering a solution to all the problems stated above.

The VitalPro chest strap from Tymewear measures your breathing rate and volume which in turn allows you to test for your metabolic thresholds. It also provides all the things listed above that are needed for continuous improvement to your fitness level, real-time guidance, personalized workouts, and actionable insights. With precise measurement of VT1, Balance Point, VT2, and VO2max, you can train smarter and unlock your true potential.

Start your journey today and experience the power of threshold-based training with Tymewear.