If you’re an athlete, you’ve likely heard about training zones. But what exactly are they? And why do they matter so much?
Heart rate training zones reflect the metabolic states your body undergoes as it transitions from one exercise intensity to another.
In simple words, they are heart rate ranges (e.g., 123 – 142 beats per minute), each one corresponding to an exercise intensity where your body responds metabolically in a specific way.
For example, your metabolic response in Zone 2 (e.g., 112 – 126 beats per minute) can be drastically different from that in Zone 3 (e.g., 127 – 135 beats per minute). This means two things: 1) The fuel mix your cells use in each zone is different (i.e., the balance between fats and carbohydrates), and 2) The capabilities your body develops in each zone are different. 
Consequently, depending on the training zone you are in, you’re using a different mix of fats and carbohydrates, accumulating fatigue at a different rate, and training other elements of your physiology. Here’s what you get from each zone:
Zone 1
Training intensity is typically used for warmup or active recovery (i.e., recovering from intense exercise while moving)
Zone 2
Zone 2 training will develop your mitochondrial function and improve your fat-burning efficiency.
Zone 3
Zone 3 training can help strengthen your lung muscles and improve heart function.
Zone 4
Zone 4 training will help improve your VO2max and ability to sustain high-intensity exercise for prolonged durations by enhancing your body’s ability to clear fatigue metabolites.
Zone 5
Zone 5 training will help improve your VO2max and peak power output capability (e.g., maximum speed or cycling wattage).
It’s essential to keep in mind that training zones are determined by your metabolism and therefore can vary vastly from those predicted by equations or wearables, which can be up to 25% off. 
Your training zones should be the compass of every training and race day. For your training session to have a purpose, they need to be making your body better in the areas where it’s lacking, and that’s only possible by following a training plan based on personalized training zones. To ensure you do your absolute best in every race, you need to be cruising at the training intensity that’s metabolically sustainable for your body, and that’s again only possible by following a racing strategy based on personalized training zones. In simple words, without knowing your actual training zones, you are essentially training or racing blindly.
The PNOE metabolic analyzer provides gold-standard accuracy in determining your training zones along with the plan that puts them to practical use. The PNOĒ test takes about 10 minutes to complete, and all it requires is a short bout of exercise while wearing the PNOĒ mask, which collects and analyzes your breath.
