The Physiological Mechanism behind the Talk Test

The Talk Test (TT) is a very simple marker of exercise intensity, which has been shown to be a useful surrogate of the ventilatory (VT) and respiratory compensation (RCT) thresholds. The purpose of this study was to evaluate a potential mechanism behind the TT. Healthy, college-aged subjects (n=20) performed a maximal and two sub-maximal cycle ergometer tests. The two submaximal tests were performed: with the Talk Test (EXP) and without speaking (the control trial – CON). Oxygen uptake (VO2), CO2 output (VCO2), minute ventilation (VE), breathing frequency (BF), end-tidal CO2 pressure (PETCO2) and TT times were recorded. VO2, VCO2 and VE were reduced during the TT and increased immediately after it. BF was reduced during the TT. PETCO2 values (a surrogate of PaCO2) were highest during the TT and lowest before the TT. The time to complete the TT increased across progressive stages. This study supports the hypothesis that talking causes CO2 retention, which may cause ventilatory drive to increase. Since the ventilatory drive is already high above the VT, the apparent CO2 retention associated with speech may cause talking to become uncomfortable.