The Importance of Accurate Thresholds

Polar's Sport Tester PE 2000 came out in 1982 and since then heart rate has been the standard measurement of intensity along with speed for endurance exercise (1). It has proven to be a very useful way to measure the physiological effort of the human body during exercise. 

The need to target specific intensities during exercise gave rise to formulas that calculated heart rate zones that would estimate an individual's true training thresholds. However, an individual’s heart rate is not only determined by how hard they are exercising. Factors like individual genetics, stress, heat, caffeine consumption, and how well-rested an individual is will change how the heart responds day to day and between individuals (2)(3). These factors add up to a 29% error margin when using heart rate alone to determine an individual's ideal exercise intensity (5). 

It soon became evident that these formulas were delivering very mixed results. 12-week long randomized control trials have found that 60% of participants do not improve their VO2max at all when using heart rate reserve to guide their exercise intensity (4). Meanwhile, in the same studies, 100% of subjects improved when using their accurate thresholds. Another study showed that for trained individuals to improve their fitness, it is not sufficient to determine training zones as percentages of their max heart rate or VO2max. It was necessary to use their unique anaerobic threshold (5).

To date, the most accurate way to determine your training intensities is either with a metabolic or a lactate test. Both tests determine the unique intensities at which you can train to improve your fitness. For metabolic testing, these two points are determined from your breathing and are called the First Ventilatory Threshold (VT1) and the Second Ventilatory Threshold (VT2) (6). 

The important thing about these tests is that they are highly individual. This means that two athletes with the same HRmax or VO2max could have very different VT1 and VT2 effort levels. It is like comparing the gears in cars with different capabilities. Some can reach 12000 rpm before having to change gears, while others will only go up to 5000 rpm. Having larger gears, for example by having a high VT1, is an indication of good metabolic ability and better overall endurance. When each individual’s unique spectrum is known, it can be trained and improved. This is how you go faster, for longer. 

We’ve compiled an infographic to explain why Ventilatory Thresholds are the gold standard of measurement in performance labs and how the error margin from heart rate-derived zones can hinder your training and performance improvement. In a future post, we’ll cover how an athlete can take the information from their VT1, VT2, and VO2max to create an effective training plan. 

1. https://books.google.is/books?id=ObUUAQAAMAAJ&q=isbn:9780963463302&dq=isbn:9780963463302&hl=en&sa=X&ved=2ahUKEwiIx4Til9DrAhWG2aQKHaIBCWAQ6AEwAHoECAAQAg
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2164943/#:~:text=The%20results%20of%20this%20study,in%20non%2Dhabitual%20caffeine%20users.
3. https://www.ncbi.nlm.nih.gov/books/NBK236240/#:~:text=Heat%20stress%20reduces%20a%20person's,somewhat%20abated%20by%20heat%20acclimatization.
4. https://bmcsportsscimedrehabil.biomedcentral.com/articles/10.1186/s13102-015-0011-z
5. https://pubmed.ncbi.nlm.nih.gov/10487378/
6. https://pubmed.ncbi.nlm.nih.gov/8425510/
7. https://www.nytimes.com/2001/04/24/health/maximum-heart-rate-theory-is-challenged.html#:~:text=In%20a%20study%20published%20in,514%20healthy%20people%20they%20recruited.