Key Takeaways

1. Resting heart rate (RHR) should be measured first thing in the morning, before getting out of bed, over 3–5 consecutive days to get an accurate baseline average.
2. The 208 – (0.7 × age) formula for maximum heart rate is 5–10% more accurate than the older 220 – age formula for most healthy adults.
3. Each heart rate zone aligns with a specific fitness goal: Zone 1 for recovery, Zone 2 for building endurance, Zone 3 for aerobic capacity, Zone 4 for lactate threshold improvement, and Zone 5 for maximum power.
4. Heart rate training outperforms fixed pace training for most people because it accounts for daily variables like sleep quality, stress, hydration, and fatigue that change your body's response to exercise.
5. Adjusting your workout intensity to stay in your target zone leads to more consistent adaptation and reduces the risk of overtraining or injury from pushing too hard on low-energy days.
6. Individual variance is significant: up to 15% of people have a maximum heart rate 10–15 beats per minute higher or lower than the formula prediction, so always adjust based on how you feel.