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Rethinking the Exercise ‘Talk Test’
By GRETCHEN REYNOLDS 21 de septiembre 2011, 12:01A.M
With the question: Can you speak aloud while working out? Researchers demonstrate the importance of exercise and talking at the same time
Many of us rely on the so-called talk test to gauge a workout’s intensity. It is such a simple measure, consisting of only one question: Can you speak aloud while working out? If so, conventional wisdom says, you are exercising at the right intensity to improve both your health and fitness.
But a new study by researchers at the University of New Hampshire suggests that we may need to refine our thinking about the talk test. For some of us, it seems, gabbing easily with a partner could be shortchanging our training.
For the study, the researchers recruited 15 healthy and active men and women ranging in age from 18 to 35. The volunteers were not competitive athletes, but most possessed above-average fitness. They were not new to exercise.
All of the participants began the experiment with testing to quantify how hard they could exercise. The researchers looked at measures like maximum heart rate and oxygen-carrying capacity, or VO2 max, a measure of how efficiently oxygen is delivered to muscles. They also looked at something called lactate threshold, the point at which the muscles tend to give out. As the intensity of your workout increases, you move closer to your particular physiological ceiling, the moment at which your body can no longer keep moving.
In a separate session, each volunteer then recited the Pledge of Allegiance aloud while jogging on a treadmill at an increasingly brisk pace. Every three minutes, he or she would repeat the pledge and tell the scientists whether speaking now was easy, difficult or close to impossible (amounting to a gasped “can’t talk”). Throughout the session, the researchers tracked each volunteer’s heart rate and other measures of exertion.
What they discovered was that people who are already fit start to have considerable difficulty talking when they approach their lactate threshold.
If that finding sounds abstruse, you probably are among the many of us who have been blissfully unaware of the significance of our lactate thresholds. Lactate, or lactic acid (the terms are used interchangeably by most people), is a chemical produced by straining muscles. It was once considered a toxin that would build up in muscles, affecting their ability to contract and leading to fatigue, but most physiologists now believe that lactic acid is in fact a cellular fuel and does not contribute to fatigue. Problems can arise, though, when strenuous exercise causes the production of lactic acid to exceed the body’s ability to clear it from muscles — a physiologic moment known as the lactate threshold.
Your lactate threshold, it turns out, plays a critical role if you wish to become more fit. Multiple studies and practical experience have shown, persuasively, that to increase your endurance and speed, you need to work out occasionally at a strenuous intensity that hovers just below your lactate threshold.
But if you can talk easily while exercising, you are not at that point, says Timothy J. Quinn, a professor at the University of New Hampshire and lead author of the new study.
You will be, instead, working out at a moderate intensity. According to the American College of Sports Medicine, moderate exercise requires 70 to 85 percent of your heart rate maximum, or 60 to 80 percent of your VO2 max. In Dr. Quinn’s study, when fit volunteers recited the Pledge of Allegiance without much difficulty, they were using, on average, 82 percent of their heart rate max and 64 percent of their VO2 max, “at the low end” of the moderate-intensity scale, Dr. Quinn said.
One reason so many of us have heard that we should be able to converse throughout a workout, Dr. Quinn says, is that many earlier studies of the talk test used volunteers who were unfit or sedentary. These individuals’ heart rates tend to be notably higher even when they can talk easily, suggesting that for the unfit, having difficulty talking does mean that heart rates were are too high.
So if you are a beginning exerciser or not competitive, the standard talk test remains a good idea. The latest American College of Sports Medicine exercise recommendations, issued in July, say that to improve your health, you should aim for 30 minutes a day of simple, moderate-intensity exercise. In practice, that means that your exercise sessions should be performed at an intensity at which “you can easily carry on a conversation with an exercise partner,” Dr. Quinn says.
But if your exercise goals are physically loftier — if you dream of significantly increasing your endurance, for example, or lowering your 5K race time — then you probably need to rethink how you use the talk test. “Based on our results,” Dr. Quinn says, “you will need to increase the intensity of the exercise to the point where talking becomes difficult” in at least some of your weekly workouts.
Muttering under your breath does not count; for the talk test to be effective, you must speak aloud, though it needn’t be the Pledge of Allegiance. When you become unable “to complete a sentence without catching your breath” on your next run or bike ride, Dr. Quinn says, you are at the cusp of the lactate threshold — and are most likely improving your fitness.
