Training Zones
The Zones tool analyzes your workout data to show how much time you spent in each training zone, based on your heart rate and/or power data.
Requirements
This tool requires:
- Heart rate data - for HR zone analysis (from a heart rate monitor)
- Power data - for power zone analysis (from a power meter)
At least one of these must be present in your file. If neither is available, the tool will not open.
Setting Your Threshold Values
LTHR (Lactate Threshold Heart Rate)
Your LTHR is the heart rate you can sustain for about an hour during an all-out effort. To find it:
- Do a 30-minute solo time trial (best effort)
- Record your average heart rate for the last 20 minutes
- That's your LTHR
The value is saved to your browser and will be remembered for future sessions.
FTP (Functional Threshold Power)
Your FTP represents the maximum power you can sustain for an hour. To find it:
- Do a 20-minute all-out effort
- Take your average power for those 20 minutes
- Multiply by 0.95 (to estimate the 60-minute value)
The value is saved to your browser and will be remembered for future sessions.
Heart Rate Zones
The tool uses Joe Friel's heart rate zone system, with different zones for running and cycling:
Running Zones
| Zone | Name | % of LTHR | Description |
|---|---|---|---|
| Z1 | Recovery | <85% | Active recovery |
| Z2 | Aerobic | 85-89% | Endurance building |
| Z3 | Tempo | 90-94% | Aerobic capacity |
| Z4 | SubThreshold | 95-99% | Lactate threshold |
| Z5a | SuperThreshold | 100-102% | VO2max intervals |
| Z5b | Aerobic Capacity | 103-106% | Anaerobic capacity |
| Z5c | Anaerobic | >106% | Neuromuscular power |
Cycling Zones
| Zone | Name | % of LTHR | Description |
|---|---|---|---|
| Z1 | Recovery | <81% | Active recovery |
| Z2 | Aerobic | 81-89% | Endurance building |
| Z3 | Tempo | 90-93% | Aerobic capacity |
| Z4 | SubThreshold | 94-99% | Lactate threshold |
| Z5a | SuperThreshold | 100-102% | VO2max intervals |
| Z5b | Aerobic Capacity | 103-106% | Anaerobic capacity |
| Z5c | Anaerobic | >106% | Neuromuscular power |
Power Zones
Power zones are based on percentage of FTP:
| Zone | Name | % of FTP | Description |
|---|---|---|---|
| Z1 | Recovery | <55% | Active recovery |
| Z2 | Endurance | 55-74% | Aerobic endurance |
| Z3 | Tempo | 75-89% | Aerobic capacity |
| Z4 | Threshold | 90-104% | Lactate threshold |
| Z5 | VO2max | 105-120% | Aerobic power |
| Z6 | Anaerobic | >120% | Anaerobic capacity |
Understanding the Results
Bar Charts
The bar charts show time spent in each zone. Taller bars indicate more time in that zone. This helps you understand:
- Was the workout easy (mostly Z1-Z2)?
- Was it a tempo effort (mainly Z3)?
- Did you do threshold work (Z4)?
- Were there hard intervals (Z5+)?
Zone Statistics
Below each chart, you'll see:
- Time spent in each zone (h:mm:ss format)
- Percentage of total workout time
- Heart rate or power ranges for each zone (based on your threshold)
Summary Statistics
The summary section shows:
- Total Time - Duration of analyzed data
- Activity Type - Running or cycling (affects zone percentages)
- LTHR/FTP - Your saved threshold values
- Average HR/Power - Workout averages
- Time Above Threshold - High-intensity work duration
- Intensity - Average power as percentage of FTP
Activity Type
Select the correct activity type (Running or Cycling) as this affects the zone calculations. The tool will attempt to detect this from your file's metadata, but you can override it.
Notes
- Zone calculations use time-weighted analysis based on timestamps
- Your threshold values are stored in browser localStorage
- If you get a new threshold test result, just update the value
- Zone definitions are based on Joe Friel's widely-used training zone system
- Reference: TrainingPeaks - Joe Friel's Quick Guide to Setting Zones