VT1, VT2, and VO2Max: Unpacking the Science of Thresholds – Tyme Wear™

VT1, VT2, and VO2Max: Unpacking the Science of Thresholds

Pack of marathoners running towards the camera

Cardiorespiratory fitness, typically determined by maximal oxygen uptake (VO2max), is an essential measurement for exercise physiologists, coaches, athletes, and other health professionals. Our cardio-respiratory system is an incredible machine that can adapt to help an athlete perform stronger, faster, and more efficiently. When an athlete improves their cardio-respiratory fitness, the body has accomplished three major changes:

  1. Increased supply of oxygen-rich blood to the working muscles
  2. Improved ability for our muscles to pull and utilize the oxygen from the blood stream
  3. Increased fuel efficiency of the working muscles

According to the American Heart Association, the capacity of an individual's cardiorespiratory fitness has been viewed as the best indicator of a person's overall health. The intensity at which one trains is arguably one of the most critical components when it comes to prescribing exercise in order to improve cardio-respiratory fitness (Wolpern, Burgos, Janot, & Dalleck, 2015).  


What is VO2Max, VT1, and VT2?

At VO2max the athlete is at a 9 out of 10 on the perceived effort level scale. It is the maximum capacity of the body to breathe in, transport, and use oxygen during exercise (work) and reflects a person’s overall cardiorespiratory fitness. A deconditioned athlete has a lower VO2max than someone who is conditioned. As an athlete becomes more conditioned, their VO2max will increase. Before reaching VO2max, an athlete will traverse their two "Metabolic Thresholds": first ventilatory threshold (VT1) and the second ventilatory threshold (VT2).

When an athlete passes VT1 they are at an effort level associated with 3 out of 10. The intensity can be observed by elevated but comfortable breathing, and despite an increase in overall lactate production and associated by-products, the body is able to clear it as quickly as it is produced. At this point, the athlete is breathing comfortably and could hold a conversation. As the intensity of the exercise increases towards VT2, breathing begins to rise to the point where they can no longer comfortably talk while exercising.

When an athlete passes VT2 they are at an effort level associated with 7 out of 10. As the effort level increases above VT2, breathing and lactate will increase exponentially. Due to the high rate of breathing, the athlete can only string a couple of words together at a time. At this point, the duration of exercise decreases due to the intensity level. VT2 is also known as the anaerobic threshold (AT).

A less conditioned athlete will reach VT1, VT2, and VO2max at a lower intensity of exercise than a more conditioned athlete. For example, a deconditioned athlete may arrive at his or her VT1 at a moderate walking pace while a conditioned athlete will reach their at a moderate running pace.

Image 1 Metabolic Thresholds VT1 and VT2 relative to 3-zone model and exercise intensity


What is Max Heart Rate?

For many years exercise intensity has been measured using heart rate. The maximum heart rate (HRmax) for an individual was used to make specific exercise-intensity recommendations. A mounting body of research has shown that formulas relying on max Heart Rate or Heart Rate reserve to prescribe an individual's effort zones have an error margin of 29% (Myers et al, 1999). The reason for this inaccuracy is due to the fact that an individual’s HRmax, whether measured in a test or calculated from an age-based formula, is governed by more than just his or her age or fitness level.

Why is using VT1 and VT2 more accurate in measuring exercise intensity?

By knowing where the true intensity markers of VT1, VT2, and VO2max are, an athlete can tailor training progressions to their individual fitness level. Working above resting levels but below VT1 is a safe way to build fitness in deconditioned athletes and is key to increasing fat utilization for all fitness levels. This improves our overall running economy by increasing the intensity level at which our bodies begin to rely on our limited carbohydrate supply for fuel. Working at and slightly above VT2 helps maximize the body's ability to consume lactate which translates to our ability to go faster for longer. Targeting VO2max during short and intense intervals trains the body to utilize a greater amount of oxygen, thereby raising the ceiling of our fitness potential. Combining these effort levels in the right way and the right duration throughout a training cycle results in optimal improvement for the least amount of work.

If you'd like to dive deeper into your VT1, VT2, and VO2max we highly recommend our blog Thresholds: The Key to Maximum Training Benefit

Learn more about how Tyme Wear can help you measure VT1, VT2, and VO2max from your breathing and adapt them to your training.



  1. Blair, S. N., Kampert, J. B., Kohl, H. W., Barlow, C. E., Macera, C. A., & Paffenbarger, R. S. (1998). Influences of cardiorespiratory fitness and other precursors on cardiovascular disease and all-cause mortality in men and women. Journal of American Medical Association, 30(6), 899-905. https://doi.org/10.1097/00005768-199806000-00019
  2. Meyer, T, Gabriel, HH, Kindermann, W. (1999) Is determination of exercise intensities as percentages of VO2max or HRmax adequate? Medicine & Science in Sports & Exercise, Volume 31, Issue 9, 1342-1354. https://doi.org/10.1097/00005768-199909000-00017
  3. Wolpern, A. E., Burgos, D. J., Janot, J. M., & Dalleck, L. C. (2015). Is a threshold-based model a superior method to the relative percent concept for establishing individual exercise intensity? A randomized controlled trial. BMC Sports Science, Medicine, and Rehabilitation, 7(16), 1-9. https://doi.org/10.1186/s13102-015-0011-z

Arnar Larusson

Arnar Larusson is the Co-Founder and CEO of Tyme Wear, a smart shirt that tracks breathing to help athletes measure their unique metabolic thresholds and individualize their training to them. Prior to founding Tyme Wear, Arnar did research at Harvard University where he helped develop the first soft exoskeleton that lowered the metabolic cost of walking. Prior to that, he helped to develop prosthetic limbs for Paralympians at Össur. Arnar is a triathlete, ultra-marathoner, and a former basketball player on Iceland’s youth national team. He holds a degree in Mechanical Engineering from the University of Iceland.