Data showed that the Talk Test related best to the lactate threshold as compared to the ventilatory threshold
"Everybody's thought that the Talk Test related well to the ventilatory threshold," Quinn says. "And it does, to a certain degree. But different physiological phenomena occur at each threshold, and it is the phenomena associated with the lactate threshold that relate better to the different levels of the Talk Test."
Quinn says these findings on the relationship of the Talk Test to the lactate threshold make the Talk Test relevant to endurance athletes as well as beginning exercisers. "In order to enhance endurance performance, some training has to occur around the lactate threshold intensity level. When subjects in the study had difficulty talking, they were very close to that lactate threshold intensity. Because of this, athletes could gauge their intensity based on ability to talk comfortably."
"If you are beginning an exercise program and can still talk while you're exercising, you're doing OK," Quinn says. "But if you really want to improve, you've got to push a little bit harder."