Zone 2 Intensity: A Critical Comparison of Individual Variability in Different Submaximal Exercise Intensity Boundaries.
Level 4 - case-series / case-control
Cross-sectional physiological study evaluating measurement variability across exercise testing markers in a single cohort
PubMed 40225831 · doi:10.1155/tsm2/2008291
What was done
Fifty cyclists (30 males, 20 females) completed laboratory incremental ramp and step exercise tests. Researchers measured power output, heart rate, blood lactate, ventilation, and substrate utilization to evaluate intra- and interindividual variability among commonly used Zone 2 (Z2) intensity boundaries.
What was found
Coefficients of variation (CV) across Z2 intensity markers ranged from 6% to 29%. Ventilatory Threshold 1 (VT1) and maximal fat oxidation (Fat Max) showed strong alignment, whereas fixed percentages of maximum heart rate (HRmax) and blood lactate thresholds exhibited wide individual differences.
Why it matters
Standardized Zone 2 prescriptions based on fixed percentages of maximum heart rate often misalign with actual metabolic status, supporting individualized physiological testing (such as VT1 or Fat Max) to accurately target low-intensity endurance zones.
Limits
The study was confined to 50 cyclists in a laboratory setting, limiting generalizability to other endurance disciplines or broader populations. The abstract reports CV ranges (6%–29%) but omits exact threshold values, specific metric-by-metric CV figures, and statistical dispersion metrics. Longitudinal training adaptation outcomes from personalized versus fixed prescriptions were not evaluated.
Cited by
- supports Zone 2 exercise corresponds to the intensity where mitochondrial fat oxidation is maximized and blood lactate levels remain steady without continually rising.