Effects of incremental cardiorespiratory exercise on the speech rate and the estimated exercise intensity using the counting talk test

[Purpose] This study examined how incremental cardiorespiratory exercise may affect the speech rate and Counting Talk Test (CTT)-estimated exercise intensity. [Participants and Methods] Twenty-four healthy adults performed the CTT while exercising on a treadmill at 6 stages of incremental exercise ranging from 40% to 85% of heart rate reserve (HRR). Each participant started walking on the treadmill at 3 to 4 km/h and 0% elevation to warm up. The increments of treadmill grades were adjusted until targeted heart rates corresponding to the percentages of HRR were reached. Then, the participants were asked to rate their perceived exertion while the treadmill grades were maintained for 2-minutes bouts of each exercise stage. At the last minute of the exercise stage, the CTT was performed within a single breath. [Results] The speech rates in the CTT appeared to vary significantly during exercise. Moreover, the CTT-estimated exercise intensity showed significant reductions at several exercise stages. [Conclusion] The CTT estimates exercise intensity semi-quantitatively throughout incremental exercise. However, moderate and vigorous intensities could not be significantly delineated by the current CTT method. This could be due to the variability in speech rates that were indicated as the exercise progressed.