Heart Rate Metrics in Cycling
In the era of power meters, heart rate is often overlooked, but it remains one of the most important metrics in cycling. While power measures external work (how hard you push the pedals), heart rate measures internal response (how hard your body is working to produce that power).
Bike Analytics integrates heart rate data to provide a complete view of your physiological state, fatigue levels, and efficiency.
Key Heart Rate Metrics
1. Resting Heart Rate (RHR)
Your pulse immediately after waking up. A lower RHR generally indicates better aerobic fitness. A sudden spike in RHR (by 5–10 beats) is often an early sign of overtraining, illness, or dehydration.
2. Maximum Heart Rate (Max HR)
The highest heart rate you can achieve during maximum effort. It is genetically determined and decreases with age. Bike Analytics uses it as a reference for defining your intensity zones.
3. Lactate Threshold Heart Rate (LTHR)
The highest average heart rate you can sustain for one hour. This is the physiological equivalent of your FTP. Knowing your LTHR is critical for accurate calculation of hrTSS.
Heart Rate Training Zones
We use Joe Friel's standard model for defining zones based on your Lactate Threshold Heart Rate (LTHR):
| Zone | Description | % of LTHR | Training Benefits |
|---|---|---|---|
| Zone 1 | Recovery | < 81% | Active recovery, blood flow |
| Zone 2 | Aerobic Endurance | 81% - 89% | Fat oxidation, mitochondria |
| Zone 3 | Tempo | 90% - 93% | Glycogen efficiency, muscular endurance |
| Zone 4 | Lactate Threshold | 94% - 99% | Threshold raising, lactate tolerance |
| Zone 5a | Superthreshold | 100% - 102% | Aerobic capacity |
| Zone 5b | Aerobic Capacity (VO2max) | 103% - 106% | VO2max improvement |
| Zone 5c | Anaerobic Capacity | > 106% | Explosiveness, anaerobic reserves |
What is hrTSS?
If you do not have a power meter, Bike Analytics uses hrTSS (Heart Rate-based Training Stress Score). This metric estimates training load based on the time spent in each heart rate zone relative to your fitness.
Note: Heart rate can be affected by external factors such as caffeine, stress, temperature, and fatigue (HR lag), which makes hrTSS slightly less accurate than power-based TSS for short intervals.
Efficiency Factor (EF) and Decoupling
By comparing power with heart rate, Bike Analytics calculates your Efficiency Factor (EF):
An increasing EF for the same type of workout means better aerobic fitness. We also track Aerobic Decoupling (Pa:Hr) – if heart rate rises while power stays the same, this is a sign of aerobic fatigue or dehydration.
Heart Rate Variability (HRV)
Bike Analytics integrates HRV data from your Apple Health ecosystem. HRV measures the time intervals between heartbeats and is the best indicator of the state of your autonomic nervous system. High HRV indicates good training readiness, while low HRV often signals the need for rest.