Estimation of anaerobic threshold, a classical index drawing renewed attention, by new methods without respiratory gas measurements.

A classic study from the 1920 s proposed that anaerobic meardiopulmonary exercise testing (CPX) is established as a useful clinical tool for evaluating the severity of heart failure and the limitations of activities of daily life in cardiac patients.1 Among the several key indices obtained from CPX, a long-accepted gold standard of exercise capacity is the peak oxygen uptake (V̇O2), a marker of maximal cardiac output. There have been ongoing attempts, however, to develop C