Power Zones
Power zones translate FTP or CP into practical training targets for endurance, threshold, VO2max, and sprint work.
Power Zones
Power zones break continuous power output into actionable training “gears”. They let you describe intensity with a consistent language (Z1–Z7 / Z1–Z5) and align training goals to energy systems and pacing scenarios.
Reference power: FTP
Zone percentages require a reference:
- FTP: see Functional Threshold Power (FTP)
- CP: see Critical Power (CP), especially for running-power models such as Stryd.
If you already know your FTP or CP, use the calculate power training load zones from FTP or CP to compute the boundaries.
How to interpret zone boundaries
All “% FTP” ranges below are written as non-overlapping intervals. For example:
- Z1: ≤ 55%
- Z2: 56%–75%
When a percentage is exactly a boundary (e.g. 128%), assign it consistently. Trainingload.ai usually assigns the boundary to the higher zone (e.g. 128% → Z7) to avoid ambiguity.
1. Joe Friel: 7-zone cycling model
Joe Friel’s model uses 7 zones spanning recovery through neuromuscular sprinting. It is commonly used for cycling and can be used for running if your threshold reference is appropriate.
| Zone | Name | English | % FTP | Typical use |
|---|---|---|---|---|
| Z1 | Active recovery | Active Recovery | ≤ 55% | Easy spin / recovery run; supports recovery. |
| Z2 | Endurance | Endurance | 56%–75% | LSD / aerobic base; improves aerobic capacity and fat oxidation. |
| Z3 | Tempo | Tempo | 76%–90% | Steady work; improves durability and glycogen economy. |
| Z4 | Threshold | Threshold | 91%–105% | Threshold work; improves sustainable power and threshold ability. |
| Z5 | VO2max | VO2 Max | 106%–120% | VO2 intervals; raises high-intensity aerobic ceiling. |
| Z6 | Anaerobic | Anaerobic | 121%–150% | Anaerobic intervals; improves lactate tolerance and repeatability. |
| Z7 | Neuromuscular | Neuromuscular | ≥ 151% | Short sprints / accelerations; neuromuscular recruitment. |
Source: Joe Friel
2. Jim Vance: 7-zone running model
Jim Vance’s model also uses 7 zones, but splits low intensity more finely. Z1–Z3 align well with everyday “walk / easy / steady” layering and can help fine-tune endurance and tempo control.
| Zone | Name | English | % FTP | Typical use |
|---|---|---|---|---|
| Z1 | Recovery / walking | Recovery/Walking | ≤ 80% | Recovery, warm-up, very easy. |
| Z2 | Endurance | Endurance | 81%–88% | Main aerobic endurance range; sustainable. |
| Z3 | Tempo | Tempo | 89%–95% | Higher steady intensity, approaching threshold. |
| Z4 | Threshold | Threshold | 96%–105% | Threshold work and durability. |
| Z5 | High intensity | High Intensity | 106%–115% | High-intensity intervals (upper aerobic). |
| Z6 | VO2 | VO2 | 116%–128% | VO2 intervals (boundary 128% is often assigned to Z7). |
| Z7 | Anaerobic capacity | Anaerobic Capacity | ≥ 128% | Short reps focusing on anaerobic capacity and explosiveness. |
Source: Jim Vance, Run with Power
3. Stryd: 5-zone running model
The Stryd model merges the high-intensity end into a simpler 5-zone structure for running. It typically uses CP as the reference, but the percentage mapping is the same if you use FTP.
| Zone | Name | English | % FTP | Typical use |
|---|---|---|---|---|
| Z1 | Easy | Easy | ≤ 80% | Recovery runs and easy running. |
| Z2 | Moderate | Moderate | 81%–90% | Steady endurance runs; long-run main intensity. |
| Z3 | Threshold | Threshold | 91%–100% | Core range for threshold and tempo work. |
| Z4 | Interval | Interval | 101%–115% | VO2 / high-intensity intervals. |
| Z5 | Repetition | Repetition | ≥ 116% | Short reps, sprints, anaerobic bursts. |
Source: Stryd
How to calculate your zone boundaries
Let your reference power be (either FTP or CP). To compute a boundary, multiply the percentage by :
W = B * (pct / 100)Example: FRIEL Z2 (56%–75%)
Assume :
Z2_min = 250 * 0.56 = 140 W
Z2_max = 250 * 0.75 = 187.5 WSo your Z2 is roughly 140 W – 188 W (actual display may be rounded to whole watts).
Trainingload.ai Advice
Trainingload.ai uses power zones to compare planned intensity with completed intensity:
- Set thresholds per sport: running and cycling power differ. Maintain CP/FTP separately and pick the appropriate model.
- Update regularly: FTP and CP change with training; re-test periodically or use auto-estimation so zones stay relevant.
- Treat zones as target bands: boundaries are not walls. The goal is to keep most work aligned with the intended training stimulus.
- Review completed workouts: after a session, zone distribution can show whether an easy day drifted too hard or a key interval session missed the intended range.