Abstract: BACKGROUND: Blood flow restriction combined with aerobic exercise has potential training benefits, and talk test is a convenient option for prescribing the exercise intensity. Whether the talk test can be applied to the blood flow restricted aerobic exercise depends on the reliability and validity of the talk test under blood flow restriction.
OBJECTIVE: To explore the reliability and validity of talk test with blood flow restriction. 
METHODS: Twenty collegiate males participated in one maximum oxygen uptake test (Tmax) and three talk tests. The protocols for the three talk tests were the same, with the one equipped with a gas metabolizer (TT-gas) throughout the whole test process, and the other two following the standard procedure (TT-standard). In Tmax, the maximum oxygen uptake, ventilatory threshold and respiratory compensation threshold were examined. In TT-standard, the corresponding heart rate and rating of perceived exertion of the last positive stage, equivocal state and negative stage were examined. In TT-gas, the corresponding oxygen uptake, heart rate and rating of perceived exertion of all steps were examined. All the four tests were fully pressurized along the bandages on both thighs (40% arterial occlusion pressure). 
RESULTS AND CONCLUSION: The reliability of corresponding power of the last positive stage and negative stage measured by two TT-standard was high. The reliability of corresponding heart rate of the last positive stage, equivocal state and negative stage was high to very high. However, the reliability of corresponding rating of perceived exertion of the last positive stage, equivocal state and negative stage was low to medium. The correlation between corresponding oxygen uptake, heart rate and rating of perceived exertion of the last positive stage and ventilatory threshold was medium to high (R=0.47-0.63, P < 0.05). The correlation between corresponding oxygen uptake, heart rate and rating of perceived exertion of the equivocal state and ventilatory threshold is high to very high (R=0.63-0.84, P < 0.05). The correlations between corresponding oxygen uptake, heart rate and rating of perceived exertion of the negative stage and ventilatory threshold were medium (R=0.36, P > 0.05), very high (R=0.80, P < 0.01) and medium (R=0.52, P < 0.05), respectively. Except for corresponding heart rate of the last positive stage, there was no significant difference between corresponding oxygen uptake, heart rate and rating of perceived exertion of the last positive stage and equivocal state and ventilatory threshold values (P > 0.005). There was no significant difference between corresponding oxygen uptake and heart rate of the negative stage and respiratory compensation threshold (P > 0.005). To conclude, the talk test in aerobic exercise with blood flow restriction under 40% arterial occlusion pressure has high retest reliability and medium to high validity, which can effectively evaluate the intensity of ventilatory threshold, but cannot effectively evaluate the intensity of respiratory compensation threshold. Talk test can be a convenient and reliable option for monitoring low intensity during blood flow restricted aerobic exercise.

Key words: talk test, blood flow restriction, exercise intensity, ventilation threshold, respiratory compensation threshold