Breath-by-breath indirect calorimetry. Hover or touch to inspect real-time metabolic kinetics.
Computed via stoichiometric indirect calorimetry equations:
Fat (g/min) = 1.67·VO₂ - 1.67·VCO₂ | CHO (g/min) = 4.55·VCO₂ - 3.21·VO₂
| Zone | HR Target | Primary Fuel | Physiological Purpose |
|---|
Direct measurement of oxygen consumption and carbon dioxide exhalation eliminates guesswork from heart rate formulas.
RER represents VCO₂ divided by VO₂. At rest and low intensities where fats are the primary fuel, RER hovers around 0.70 to 0.82 because fat requires more oxygen atoms per carbon oxidized. As intensity rises toward threshold, RER reaches 1.00 (100% carbohydrates) and passes 1.10 as lactic acid buffering releases excess non-metabolic CO₂.
VT1 (Aerobic Threshold) is detected when VE/VO₂ rises while VE/VCO₂ remains flat—the ceiling of pure Zone 2 endurance where fat oxidation is maximized. VT2 / RCP (Respiratory Compensation Point) marks where hyperventilation begins to compensate for systemic metabolic acidosis.
Compact breath masks measure gas concentrations (O₂ and CO₂) combined with differential pressure flow sensors. By utilizing rapid progressive ramps, individuals can measure their genuine VO₂ max, metabolic efficiency, and personalized zones right on commercial gym cardio equipment in under ten minutes.