For cyclists, training by heart rate is one of the most effective ways to ensure you are riding at the correct intensity to meet your goals. Whether you are training for a 100-mile century ride or looking to improve your sprinting power, understanding your zones prevents the common mistake of riding "too hard on easy days and too easy on hard days."
The Karvonen Formula
This calculator uses the Karvonen Method, which is more accurate than simple percentages because it accounts for your Heart Rate Reserve (HRR). HRR is the difference between your maximum heart rate and your resting heart rate. By incorporating your fitness level (resting heart rate), the zones become much more specific to your current physiology.
Breakdown of Cycling Zones
Zone 1: Active Recovery (50-60% HRR) Used for recovery rides the day after a hard race or interval session. It stimulates blood flow to the muscles without adding fatigue.
Zone 2: Endurance (60-70% HRR) The "Base" zone. This is where you build aerobic capacity and teach your body to burn fat efficiently. You should be able to hold a conversation in this zone.
Zone 3: Tempo (70-80% HRR) Moderate intensity. Used for building aerobic power. It feels "comfortably hard." Conversation becomes shorter.
Zone 4: Lactate Threshold (80-90% HRR) High intensity. This is roughly the pace you could sustain for a 40-60 minute time trial. Used to increase your maximum sustainable speed.
Zone 5: Anaerobic / VO2 Max (90-100% HRR) Maximum effort. Used for short intervals, sprinting, and steep climbs. These efforts are usually sustained for 30 seconds to 5 minutes.
Example Calculation
If a 40-year-old cyclist has a resting heart rate of 60 BPM: