Intensity.si
Your guide to training intensity and workout zones
Intensity.ai explains how exercise intensity actually works - heart rate zones, RPE (rate of perceived exertion), VO2 max, and how to structure interval training. Understand the science behind training hard so your workouts match your goals. Educational only - not medical advice; talk to a doctor before starting a new exercise program, especially with any health condition.
No card required · $9/mo Plus · $99/mo Premium
What you get
Everything Intensity.si gives you
Heart rate zones
Estimate and understand zones 1 through 5 for your training goals.
RPE scale explained
How rate of perceived exertion works and when to use it over a monitor.
Interval structuring
How intensity and rest periods combine in effective interval workouts.
Saved training notes
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Go deeper
Understanding Training Intensity
The science behind how hard you're actually working, and how to use it.
Measuring Intensity
- Heart rate reserve — A method using resting and max heart rate to set personalized zones.
- RPE (Borg scale) — A 6-to-20 or 1-to-10 scale for rating perceived effort without equipment.
- VO2 max — A measure of the body's maximum oxygen use, linked to aerobic fitness.
Applying It
- Zone 2 training — Low-intensity, sustainable effort often used to build aerobic base.
- HIIT structure — Short, high-intensity efforts paired with recovery periods.
- Lactate threshold — The intensity where lactate builds up faster than the body clears it.
Pricing
Simple plans that grow with you
Plus
$9/mo
- ✓200 questions per day
- ✓Full saved conversation history
- ✓Personalized zone estimate walkthroughs
Premium
$99/mo
- ✓Unlimited questions
- ✓Extended deep-dive answers
- ✓Everything in Plus