What’s the Hype with Heart Rate Zone Training and VO2max?

What’s the Hype with Heart Rate Zone Training and VO2max?

Rhiannon Jardim, DPT, PT, CSCS

VO2max measures the maximum amount of oxygen your body can use during intense exercise, giving you a sense of how efficiently your body generates energy with maximal effort. This is often used to predict overall performance– which is why so many athletes are curious to know their “number”!

Generally, as you run longer and harder, the body’s total energy demands rise.

First these demands are met using aerobic metabolism (all oxygen). As intensity continues to rise, the body shifts to using anaerobic metabolism (creating energy without oxygen) because the oxygen demands aren’t being met. Think of it like this, your muscles are working hard, demanding more and more oxygen, but there is only so much blood in the body to deliver it. Working at this capacity is unsustainable for long periods of time – there’s only a limited amount of energy that your body can create while in an oxygen deficit. Additionally, during anaerobic exercise, the body isn’t able to clear and recycle the waste build up (lactate) at the same rate it’s created, which leads to that fatigue and burning sensation in the muscles. Reminder: VO2 max is measuring how efficient your body is at using oxygen as its source of energy.

So how would a runner incorporate these different systems into their training?

When looking to optimize your VO2max, you’re trying to push back the timeframe when the body switches from aerobic to anaerobic metabolism. You’re also looking to be able to sustain the buildup of byproducts (like lactate) in your system for a longer period of time. Heart rate training based on Zones 1-5 are commonly used to do this. While specific percentages may vary, a general sense of these zones are as follows:

Simply put, Zones 1 and 2 improve your cardiovascular health and aerobic endurance, while providing a strong base for other layers to be built upon. You can think of this like a pyramid: the larger your base the higher you can build. Zone 3 is where things get tricky. In Zone 3 the body is working too hard to build your aerobic base but not hard enough to get the benefits of Zones 4 and 5, which are your VO2max and anaerobic zone respectively.

Zone 2, the aerobic zone, is when lactate is steadily being recycled and reused – it’s not building up and causing those heavy legs you might feel when doing a high intensity workout. Training in Zone 2 allows you to train with high frequency (yay!) without the build up of byproducts and neuromuscular fatigue. Additionally, credentialed coaches, like our clinicians, would recommend that 70-80% of your training takes place in Zone 2 to build that solid base we mentioned before!

Research has shown that short, intense training bouts, usually sitting between Zone 4 and 5, around 90% HR Max, will help improve an athlete’s VO2 Max. Targeted work in these zones will also address the other major pillar of VO2max improvement: tolerance of byproduct build up. This allows your body to work at a high intensity for longer periods of time, even with the accumulation of lactate (as shown by the graph below).

Improving your VO2max should happen through a combination of training: steady-state training at lower intensities (Zone 2) and short, high-intensity sessions (Zone 4-5).

While high-intensity interval training is effective for quick improvements in both fitness and performance, it’s crucial to consider adequate recovery time (including rest, nutrition, and subsequent low-intensity workouts to clear byproducts).        

There’s a well-designed temptation to rely on your Garmin or Apple Watch to calculate your heart rate zones or VO2 Max for you – but if you’re truly interested in improving your VO2max, you should consider getting a comprehensive test. This one-on-one time will allow for precise and accurate data into your heart rate zones based on your current training, rather than an estimation based on your previously logged performances. With this information, and the help of a credentialed coach, you can design a future training plan to increase your VO2max and improve your overall performance.  


  1. Brownstein CG, Pastor FS, Mira J, Murias JM, Millet GY.  Power Output Manipulation from Below to Above the Gas Exchange Threshold Results in Exacerbated Performance Fatigability. Medicine & Science in Sports & Exercise 54(11):p 1947-1960, November 2022. | DOI: 10.1249/MSS.0000000000002976
  2. Haugen T, Sandbakk Ø, Seiler S, Tønnessen E. The Training Characteristics of World-Class Distance Runners: An Integration of Scientific Literature and Results-Proven Practice. Sports Med Open. 2022;8(1):46. Published 2022 Apr 1. doi:10.1186/s40798-022-00438-7
  3. Scribbans TD, Vecsey S, Hankinson PB, Foster WS, Gurd BJ. The Effect of Training Intensity on VO2max in Young Healthy Adults: A Meta-Regression and Meta-Analysis. Int J Exerc Sci. 2016;9(2):230-247. Published 2016 Apr 1.
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