The limitation of exercise ventilation during speech

Ventilation in steady-state treadmill exercise at five different speeds has been measured in six subjects using an inductance plethysmograph whose calibration is described. A printed passage of 100 words was read aloud during the fifth minute of each exercise period:this took about 30 sec. At each exercise level ventilation was reduced during speech to about 55% of the control value: at the highest level the reduction was 38 1. min-1 from a control ventilation of 78 1. min-1. Respiratory frequency was reduced but tidal volume was not affected. Twenty-four per cent of the ventilation during the speech period at the heaviest exercise was accounted for by non-phonated (silent) expirations. Immediately after the speech period, ventilation overshot by about 14% and then returned to the control value within 30 sec. The results are interpreted in terms of the precedence taken by the speech requirement for restricted expiratory airflow rates over the ventilatory requirement for gas exchange.