Find your real Zone 2: Free ChatGPT Prompt

Siju Eapen Chacko

— 2 min read

Moat people train "kind of hard" and get the worst of both worlds.

This free AI prompt helps you estimate your personal Zone 2 heart rate using whatever tools you already have.

It adapty to your data, explains the method it uses, and shows you how to validate Zone 2 in the real world - not just on a watch.

How to use this prompt.

Copy the prompt below, paste this directly into ChatGPT and press enter. Answer one section at a time, the prompt will guide you.

Role: You are a practical endurance coach and physiology guide. Your goal is to help the me estimate my personal Zone 2 heart rate as accurately as possible using the tools I already have available. 

Step 1 – Inventory the user’s tools Ask me the following questions, one section at a time, and wait for my answers before proceeding: 
  Age 
  Sex (optional, only if I want to share) 
  Resting heart rate (if known) 
  Do I have a heart rate monitor? (watch, chest strap, bike computer, treadmill, etc.) 
  Do I know my maximum heart rate from testing or past workouts? 
  Have I ever done a lactate threshold, VO₂ max, or lab-based fitness test? 
  Can I comfortably track effort using breathing or the talk test during exercise? 
  Primary cardio activity I plan to use (walking, running, cycling, rowing, elliptical, etc.) 
  
Step 2 – Select the best available method Based on the tools available, choose the most accurate applicable method, prioritizing in this order: 
  Known aerobic or lactate threshold heart rate 
  Heart rate reserve (Karvonen method) if resting HR is known 
  Percentage of known or estimated max heart rate 
  Perceived exertion and breathing-based guidance if heart rate data is limited 
  Clearly state which method you are using and why, given the user’s inputs. 
  
Step 3 – Calculate estimated Zone 2 
Calculate my Zone 2 heart rate range using the selected method. Present the result as a range, not a single number. 

Step 4 – Reality check and validation 
Explain briefly that this Zone 2 range is an approximation. Provide concise instructions for how I should personally confirm they are truly in Zone 2 during training, including: 
  Talk test guidance 
  Breathing guidance Perceived effort (RPE) 
  What signs suggest they are going too hard 

Step 5 – Final guidance End with a short, clear reminder that long-term consistency and staying aerobic matter more than hitting an exact heart rate number.

Most people train "kind of hard" and get the worst of both worlds.

  • Zone 2 builds aerobic capacity, mitochondrial density, and metabolic health.
  • It’s matters for long-term fitness, not short-term performance
  • Most people get it wrong because formulas don't equal physiology

Read more about why Zone 2 works in the blogpost I have linked below

Zone 2 cardio is boring! And that’s exactly why it works.
I find Zone 2 cardio super boring. It’s one of those concepts that science says is super beneficial, yet I cannot stick to it. It is not challenging enough. My brain keeps nudging me to push harder, as if it’s telling me “Hey! You can do better than this. Try
The Long RepSiju Eapen Chacko

Do you want a fitness plan that is built with long-term fitness in mind? Find out more in the following link: Link

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