Table 1 The units and explanations of indexes

VO_2peak

ml/min

Maximum oxygen uptake measured during exercise, reflecting overall cardiopulmonary capacity

VO_2peak/kg

ml/(kg·min)

Oxygen consumption per kilogram of body weight; a key measure of aerobic fitness and cardiopulmonary function

VO₂@AT

ml/min

Oxygen uptake at the anaerobic threshold (AT), where anaerobic metabolism supplements energy production, marked by increased lactate and L/P ratio in blood and muscle

VE/VCO₂ Slope

–

Slope of minute ventilation to CO₂ output from exercise onset to AT or RC point; reflects ventilator—perfusion efficiency

△VO₂/△WR

ml/(min·W)

Represents the efficiency of aerobic work, expressed as the increase in oxygen uptake (VO₂) relative to the increase in workload (WR). It quantifies the amount of oxygen consumed per unit of work performed. The normal range is (10.2 ± 1.0) ml/(min ·W)

VO_2peak/HR

ml/beat

Known as oxygen pulse, this parameter is calculated by dividing peak oxygen uptake (VO₂_peak) by the heart rate (HR) measured at the same time point. It reflects the amount of oxygen delivered per heartbeat, influenced by peripheral oxygen extraction and cardiac stroke volume. It is a recognized indicator of cardiovascular efficiency

OUES

–

A submaximal parameter reflecting the efficiency of oxygen uptake relative to ventilation. OUES (Oxygen Uptake Efficiency Slope) is calculated by the logarithmic relationship between oxygen consumption (VO₂) and minute ventilation (VE) during incremental exercise. It is commonly used to evaluate cardiorespiratory fitness and endurance performance, particularly in patients with cardiovascular or pulmonary conditions

PetCO₂

mmHg

End-tidal CO₂ pressure; reflects alveolar ventilation and ventilation-perfusion matching

VE/VCO_{2 lowest}

–

Minimum ventilation required to eliminate 1L of CO₂ during exercise; indicates ventilatory efficiency

VE/VO_{2 lowest}

–

Minimum ventilation required to consume 1L of O₂ during exercise; indicates ventilatory demand per oxygen unit

HR_peak

bpm

Peak heart rate recorded during exercise testing

HR_rest

bpm

Resting heart rate measured before exercise

HRR-1 min

bpm

Heart rate recovery at 1 min post-exercise; calculated as the difference between HR_peak and HR at 1 min of recovery

VE_peak

L/min

Peak minute ventilation achieved during maximal exercise

RF_peak

breaths/min

Peak respiratory frequency during exercise

FVC

L

Forced vital capacity; the maximal volume of air forcibly exhaled after full inhalation

FEV1

L

Forced expiratory volume in the first second; the volume of air exhaled during the first second of forced expiration

FEV1/FVC

%

Ratio of FEV₁ to FVC; used to assess airway obstruction, typically ≥ 70–80% in healthy individuals

AHRR

%

Adjusted heart rate reserve = (HR_peak − HR_rest)/(220 − age − HR_rest); reflects cardiovascular responsiveness