Endurance Training Zones Calculator for Runners & Cyclists

Clear definitions, scientific logic, and practical calculator for runners & cyclists for EnduroMetrics Data Field for Garmin.

Scientific Explanation

The calculator accurately computes the values entered in the Data Field settings, ensuring reliable operation both with and without lab-based measurements, even for novice athletes. When laboratory data are available, the model uses metabolic markers such as LT1/VT1, LT2/VT2, the Metabolic Efficiency Point (MEP/Crossover Point), and the Race Threshold Heart Rate (Race-LTHR) from a 30-minute field test, providing physiologically sound zone boundaries fully aligned with the scientific research of Dr. Stephen Seiler on polarized training models.
NOTE
Advanced Note:
The Race-THR obtained from the 30-minute Race Field Test is used because, in most cases, it is slightly higher than the heart rate at the metabolic LT2. This choice ensures that training aligns with the principles of the polarized model (Seiler / Schöller), with tempo workouts performed above the metabolic threshold while remaining compatible with modern training frameworks. Tempo sessions are positioned just below race-specific thresholds (sub-threshold in racing terms, not metabolic), whereas threshold workouts are defined at higher intensities as supra-threshold efforts.

Understanding Training Zones

Z1 – Recovery

Recovery: Very low intensity for restoration

Z2 – Aerobic Base

Aerobic Base: Builds endurance, easy conversational pace

TL – Transition Low

Transition Zone: No Man's Land (doesn't provide expected improvements - avoid staying in this zone during training)

Z3 – Turbo! Tempo®

Tempo workouts are performed below the race threshold (Race-THR). They are structured in blocks of 5, 10, or 20 minutes at a pace faster than half-marathon pace, approaching conditions of a 10K race. The goal is to improve endurance at high aerobic intensity without causing significant lactate accumulation.

TH – Transition High

Death Zone AVOID - doesn't provide expected improvements - avoid staying in this zone during training

Z4 – Supra-Threshold

Supra-Threshold: A high-intensity zone aimed at improving lactate endurance “buffer.” Workouts are performed at a pace faster than the classic threshold—approximately 10 seconds per kilometer faster than 10K race pace. They are structured in short intervals, such as 4–6×4 minutes or 3–4×6 minutes, allowing control of metabolic stress without excessive fatigue.

Z5 – Anaerobic

Anaerobic: Very short, high-power sets (≤20s)

Key: If you have lab-based LT1, LT2, and MEP, use these metabolic points for the most accurate zone boundaries.

If the 30' RaceTHR is higher than the metabolic LT2, calculations are done as a percentage of LTHR (field-based). If RaceTHR is equal to or below LT2, the LT2 is used as the base.

For FTP from a 30' field test, enter the 20-minute average power without the 0.95 factor (calculation is automatic). Garmin's FTP value is already adjusted with 0.95 and can be entered directly.

Recommended Input Fields

Fill in the calculator according to your testing protocol:

From ergometric test:
• LT1: Heart rate at the 1st lactate threshold (aerobic)
• LT2: Heart rate at the 2nd lactate threshold (anaerobic)
• MEP: Heart rate at the Metabolic Efficiency Point (fat/carb crossover – ask your exercise physiologist)
FTP (cyclists):
• Average 20' power from a field test
• Or Garmin FTP (as shown in Data Field Settings)
• Alternatively, power at LT2, which practically corresponds to FTP
For beginners:
• Z2 = comfortable jogging/cycling where you can talk without gasping (Zone 2)
• Perform 30' Z2 at a relaxed pace. You should be able to speak comfortably without interruption from breathlessness (we do not want a fast pace). Record and calculate average HR, Power, and Pace (for runners) from Garmin Connect charts.
• For Pace, enter in seconds/km: e.g., 5:40 → 5×60 + 40 = 340.

Training Zones Calculator
  • Use data from 30' field test (average HR & Power from best 20') to calculate accurate FTP, LTHR, MEP values and proper training zones for EnduroMetrics Data Field.
  • If you have lab test results, enter LT1 / LT2, Power at LT2 and MEP.
Example: 5:40 → 5×60 = 300 + 40 = 340 seconds
* MEP is calculated as 87.5% of LTHR. When you have ergometric test results, ask your exercise physiologist for the Heart Rate at MEP (Metabolic Efficiency Point or Crossover Point FAT=CARB) and enter this HR directly in EnduroMetrics Settings.
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