Training in heart rate zones only works if the zones are set correctly. The simplest formulas, based purely on maximum heart rate, ignore one key parameter - your individual fitness level, reflected in your resting heart rate. The Karvonen method solves this problem by using what's called heart rate reserve. In this article we explain how to apply it and calculate your target heart rate for each zone.
What is heart rate reserve?
Heart rate reserve (HRR) is the difference between maximum heart rate and resting heart rate. It shows by how many beats the heart can accelerate from a resting state to maximal effort. The lower your resting heart rate, the larger your reserve - and usually the better your cardiovascular fitness.
- Maximum heart rate (HRmax) - most often estimated with the formula 220 minus age
- Resting heart rate (HRrest) - measured in the morning, right after waking up, at rest
- Heart rate reserve (HRR) - the difference HRmax minus HRrest
The Karvonen formula
Target heart rate for a given zone is calculated with the formula: target heart rate = HRrest + (intensity percentage x HRR). By accounting for resting heart rate, the zones are matched to your individual fitness level, not just your age. This is exactly what makes the Karvonen method more accurate than simply calculating percentages of HRmax.
Worked example: calculating target heart rate
Suppose you're 35 years old and your resting heart rate is 60 beats per minute. First we calculate maximum heart rate: 220 - 35 = 185. Then heart rate reserve: 185 - 60 = 125.
You want to train at 70 percent intensity. Substituting into the formula: 60 + (0.70 x 125) = 60 + 87.5 = 147.5 beats per minute. For comparison, the lower bound of the zone at 60 percent is 60 + (0.60 x 125) = 135 beats. This means your aerobic zone falls roughly in the range of 135-148 beats per minute - much more precise than simply calculating percentages of HRmax alone.
How to use zones in training?
Low-intensity zones (60-70 percent of reserve) build an aerobic base and support recovery. Medium zones (70-80 percent) improve endurance, and high zones (above 85 percent) develop lactate threshold and speed. Most training plans are based on the principle that most training volume is done at an easy pace, with only a small portion at high intensity.
Frequently asked questions (FAQ)
1. How is the Karvonen method different from simple formulas? It accounts for resting heart rate, so the zones are matched to your fitness level.
2. How do I measure resting heart rate? Best in the morning, right after waking, before getting out of bed.
3. What is heart rate reserve? The difference between maximum heart rate and resting heart rate.
4. Is the formula 220 minus age accurate? It's only an estimate - the most accurate figure is maximum heart rate measured in an exercise stress test.
5. In which zone does the body burn the most fat? The highest share of fat is used in low and medium zones, around 60-70 percent of reserve.
6. Does a lower resting heart rate mean better fitness? Usually yes, it indicates an efficient, well-functioning heart.
7. How often should you train at a high heart rate? Usually only a small percentage of total volume, to avoid overtraining.
8. Does the Karvonen method work for beginners? Yes, it's especially useful for them, since it matches zones to current fitness.
9. Does stress affect resting heart rate? Yes, stress, lack of sleep, and overtraining can raise it.
10. Is a heart rate monitor necessary? It helps a lot, since it lets you stay in the zone in real time.
To quickly determine your heart rate zones with the Karvonen method, use the heart rate reserve calculator on Liczbnik.pl, which calculates your target heart rate for each zone.