As of 13 August 2026, AI can only partly calculate your training heart-rate zones.

What to actually do

1. Hand it to a person

   The route this page recommends

   A person who owns the outcome does this end to end, worth it when the failure is dear.

2. Use a tool built for this

   Second choice

3. Do it yourself

   The distant third

   A chat interface, chat-fluent skill, and roughly 30 minutes until you can act on the result.

   How to actually do it

   1. 1. Gather your age, resting heart rate, any measured maximum or threshold heart rate, and the heart-rate method recommended by your clinician, coach or device.
   2. 2. Record any heart condition, heart-rate-affecting medicine, previous exercise restriction or unexplained symptoms in the relevant-health section of the prompt.
   3. 3. Open ChatGPT, Claude or Gemini and paste the complete prompt with your actual inputs, leaving unknown values marked as unknown rather than guessing.
   4. 4. Answer any clarification question about the calculation method, and do not let the chatbot fill a missing maximum or threshold heart rate without labelling it as an estimate.
   5. 5. Check the displayed formula and arithmetic with a calculator, then compare every zone boundary with the settings and units shown on your watch, bike or treadmill.
   6. 6. Ask a GP, cardiac rehabilitation professional or other suitable healthcare professional to confirm the zones if you have a heart condition, take medicine that affects heart rate, have restrictions, or are unsure whether the intensity is safe.
   7. 7. Stop exercising and use NHS 111 or 111.nhs.uk for urgent or worrying symptoms, rather than asking the chatbot to assess what they mean.

   Prompt

   Calculate my training heart-rate zones using only the information below.
   
   Age: [age]
   Resting heart rate: [resting heart rate, with units]
   Measured maximum heart rate: [measured maximum heart rate, or write unknown]
   Measured threshold or lactate-threshold heart rate: [value, or write unknown]
   Heart-rate method I want to use: [for example, a clinician-approved method, maximum-heart-rate method, or heart-rate-reserve method]
   Relevant medical conditions, heart symptoms, medicines that affect heart rate, or clinician restrictions: [details, or write none known]
   
   First, state which inputs are missing or unreliable. Do not invent a value, silently select a formula, diagnose me, or present generic zones as medically suitable. If the method is not specified or more than one method is reasonable, explain the difference briefly and ask me to choose, rather than choosing for me. If I have heart symptoms, a diagnosed condition, medicines that affect heart rate, or clinician restrictions, tell me to confirm the zones with a healthcare professional. Once the method and inputs are sufficient, show the formula, calculate each zone, show the arithmetic, state the rounding used, and put the result in a clear table. Label the result as a training estimate, list what I must check against my watch or bike settings, and state that I should stop exercising and seek urgent help for worrying symptoms. Do not give a diagnosis.

   Open it prefilled in ChatGPT or Claude, or copy it into Gemini, which takes no prefill link.