By CARL FOSTER, Ph.D., and JOHN P. PORCARI, Ph.D.
Department of Exercise and Sport Science, University of Wisconsin-La Crosse

“If you can just talk, you are just about at the right exercise intensity.” I first heard this simple concept from a fellow late-night runner at the Memorial Stadium track at the University of Texas at Austin. It was the summer of 1979, and I was a first-year graduate student in exercise physiology, still in wonder as I began to learn things like VO₂max, lactate threshold, mitochondrial density and training effect. And yet here was some guy I barely knew telling me that I could design my training intensity based on being able to talk. Surely he was misguided and simply lacked the technological knowledge he needed to guide his training. But as it turned out, he was pretty much right.

Known But Not Necessarily Respected

Even in 1979, the concept of the “Talk Test” as a marker of correct exercise intensity was not really all that new. In fact, it has been around at least since 1939, when Professor John Grayson at Oxford University advised English mountaineers to “climb no faster than you can talk.” This simple idea kept kicking around on the fringes of exercise physiology, not quite technologically advanced enough to ever gain real respectability in an era of rapidly expanding technology, but never quite going away. It was included in the fourth edition of ACSM’s Guidelines for Exercise and Training in 1991, and in guidelines published by the American Council on Exercise in 1997. But despite official recognition by the major professional societies, the Talk Test never quite achieved the respectability of the Karvonen Method or the glamour of the newly emerging exercise-prescription techniques such as %VO₂max, ventilatory threshold, or techniques based on analysis of blood lactate.

In the late 1990s, Dr. Robert Goode at the University of Toronto began promoting the “hear your breathing test,’ and Dr. Steven Keteyian and colleagues at Henry Ford Hospital in Detroit demonstrated that if people could still talk well enough to answer questions to a structured interview (e.g., What did you have for breakfast this morning?), they were in a range of heart rate or VO₂ that fit the exercise prescription guidelines of ACSM.

Validating the Talk Test

It was about this time that I joined Dr. John Porcari at the University of Wisconsin, La Crosse. John and a graduate student named Meghan Dehart were talking about ways they could follow up on some of Keteyian’s work with a project on the Talk Test. First, we reasoned that the Talk Test must be close to the ventilatory threshold, since breathing frequency increases rapidly at the point of the ventilatory threshold, and the one thing you have to do to be able to talk comfortably is to control the frequency of your breathing. During practice trials in the laboratory, we figured out that the simplest way to do the Talk Test was to have the subject recite aloud a standard paragraph and then ask them if they can speak comfortably. For several exercise stages the response to our question would be a quick “Yep,” but sometime in the middle of the test the subject would begin to equivocate: “Yeah, but….” And still later in the test, when the subjects were working really hard, the answer to our question was a flat “No.”

Because you can’t talk and do gas exchange studies at the same time, we had our subjects do the same exercise tests on two different days. We found that as long as the subject was responding to our question about talking comfortably with “Yep,” that they were at an exercise intensity below the ventilatory threshold. We also observed that just at the point where the subject’s answers about speech comfort started to become equivocal, that they were right on top of the ventilatory threshold. We now had a way of doing the Talk Test that seemed to work, and had shown that it served as a surrogate for an important physiological marker—ventilatory threshold—that was otherwise only measurable in a high-tech laboratory setting. Feeling good about our results, we wrote up the research for publication and moved on to other investigations

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