A 68-year-old training in Zone 2 should target roughly 96–112 bpm, calculated as 60–70% of an estimated HRmax of 160. This is the aerobic-base zone where mitochondrial density, fat oxidation and stroke volume adapt most strongly — and the intensity you can hold in full conversation for 60–90 minutes.
60% of 160 = 96 bpm. 70% of 160 = 112 bpm. Stay inside this band for easy aerobic development.
| Zone | Name | % HRmax | BPM (age 68) |
|---|---|---|---|
| 1 | Recovery | 50–60% | 80–96 |
| 2 | Endurance | 60–70% | 96–112 |
| 3 | Aerobic | 70–80% | 112–128 |
| 4 | Threshold | 80–90% | 128–144 |
| 5 | Maximum | 90–100% | 144–160 |
If you know your resting heart rate, Karvonen gives a more accurate Zone 2. Example for a 68-year-old with RHR 60: Zone 2 = 60 + (160 − 60) × (0.60 to 0.70) = 120–130 bpm.
Most recreational athletes get the biggest return from 3–5 Zone 2 sessions of 45–75 minutes per week, plus one Zone 4 session for lactate-threshold stimulus. Sleep quality and recovery capacity become the limiter — not intensity.
A 68-year-old should aim for approximately 96–112 bpm in Zone 2, calculated as 60–70% of an estimated HRmax of 160 bpm (Tanaka).
Using the Karvonen method with a resting HR of 60, a 68-year-old's Zone 2 becomes approximately 120–130 bpm. Karvonen is generally more accurate than %HRmax for trained athletes.
Most research supports 3–5 Zone 2 sessions of 45–75 minutes per week, plus one Zone 4 threshold session. Recovery capacity becomes the main limiter as you age, not intensity.
Use the talk test: in Zone 2 you should be able to speak in full sentences comfortably. If you can only manage short phrases, you have drifted into Zone 3 or 4.
Disclaimer: This calculator is for informational purposes only and does not provide medical advice. Always consult with a healthcare professional before starting any new exercise program.
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