Key result
Watt-max test achieves true VO2max in ~77% of cardiac patients, but clinician assessment lacks specificity.
Why the study?
The criterion validity of the Watt-max test for identifying maximal oxygen consumption attainment and the accuracy of test assessors' judgement of maximal effort in individuals with heart disease in primary healthcare needed evaluation.
Does the cycle-ergometer Watt-max test accurately identify attainment of maximal oxygen consumption compared to indirect calorimetry in adults with heart disease enrolled in cardiac rehabilitation?
Cross-Sectional (n=202)
No
Does the cycle-ergometer Watt-max test accurately identify attainment of maximal oxygen consumption compared to indirect calorimetry in adults with heart disease enrolled in cardiac rehabilitation?
The cycle-ergometer Watt-max test demonstrates acceptable criterion validity for identifying V̇O₂max in cardiac rehabilitation patients in primary care, though test assessors have limited accuracy in ruling out maximal effort.
Supports cautious VO2max interpretation in rehabilitation; leaves open criterion standardization and prospective validation.
OBJECTIVE: To evaluate the criterion validity of the Watt-max test for identifying attainment of maximal oxygen consumption (V̇O₂max) in individuals with heart disease in primary healthcare. A secondary aim was to assess the accuracy of test assessors' judgement of maximal effort during the Watt-max test. DESIGN: Cross-sectional validation study. SETTING: Single-centre primary healthcare cardiac rehabilitation program. PARTICIPANTS: 202 adults with diagnosed heart disease enrolled in cardiac rehabilitation. INTERVENTION: Participants completed a cycle-ergometer Watt-max test simultaneously with indirect calorimetry, which served as the reference standard. MAIN OUTCOME MEASURES: The primary criterion for confirming V̇O₂max was the attainment of a plateau in oxygen uptake, defined as a ≤50 mL/min increase in oxygen uptake despite increased workload during the Watt-max test. Secondary criteria included respiratory exchange ratio (≥1.15), rating of perceived exertion (≥17), and maximal heart rate (≥92% of age-predicted maximal heart rate). RESULTS: Overall, 155 participants (77%) met the predefined criteria for V̇O₂max attainment. Of these, 60% demonstrated a V̇O₂ plateau, while an additional 17% met at least two secondary criteria. Assessors correctly identified 81.9% of tests in which V̇O₂max was attained during the Watt-max test. However, low specificity (34.0%) and negative predictive value (36.4%) suggest limited accuracy for ruling out maximal effort. CONCLUSION: The Watt-max test demonstrates acceptable criterion validity for identifying V̇O₂max in individuals with heart disease when conducted in a primary healthcare setting. Assessors showed fair ability to identify maximal effort, yet caution is warranted when maximal effort is assessed as not achieved.
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Sevel et al. (2026) conducted a cross-sectional in Heart disease (n=202). Cycle-ergometer Watt-max test vs. Indirect calorimetry (reference standard) was evaluated on Attainment of maximal oxygen consumption (VO2max), primarily defined by a plateau in oxygen uptake (<=50 mL/min increase despite increased workload) or at least two secondary criteria (RER >=1.15, RPE >=17, maximal HR >=92% of age-predicted maximal HR). The Watt-max test resulted in VO2max attainment in 77% of heart disease patients (60% via VO2 plateau), with assessors correctly identifying 81.9% of true maximal efforts but with 34.0% specificity.
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