Exercise Prescription Methods – The Talk Test

Posted byViktor EngmanPosted inPhysiology, Training, Uncategorized

When prescribing endurance training the two main variables that can be manipulated are duration and intensity. Whilst the former only requires a stopwatch, prescribing the ‘correct’ intensity can be a tricky task and ideally requires regular lab testing to determine the exercise intensity domains. Since most people do not have access to such equipment, variables such as heart rate (HR) or rating of perceived exertion (RPE) are commonly used. However, neither one of these can by themselves provide sufficient information to determine whether the athlete is exercising in the intended intensity zone. Instead, this article will discuss an alternative exercise prescription method – the talk test. The concept dates back to at least 1937 as the mountaineer John Grayson allegedly stated that the climbers had a rule of never climbing at a faster rate than they were able to speak at.1 Perhaps, there is some truth in that.

Exercise intensity domains

Physiologically, three aerobic exercise intensity zones can be determined based on oxygen uptake kinetics, these are demarcated by the lactate threshold (LT) and critical power/speed (CP/CS).2 There are other thresholds used to demarcate the zones, but this article will use these two as they are probably the most widely used.3 A full outline of the zones can be seen in table 1. Commonly used devices such as sport watches from Polar or Garmin have their own intensity domains, whilst these are not necessarily in line with the metabolic the load imposed on the athlete, they may still prove useful for exercise prescription.

Table 1. Exercise intensity domains.2

Heart rate for exercise prescription

Heart rate is easily measured via a chest strap or smart watch and is regularly used by amateur and professional athletes likewise. With respect to the intensity zones previously outlined, the main inherent flaw with heart rate is that it varies between and even within individuals. For example, when Iannetta et al.4 assessed the maximum heart rate (HRmax) and two indices resembling the LT and CP in 100 men and women, they found that LT varied between 60-90% of HRmax and CP (they actually assessed maximum lactate steady state, but for this article, we’ll assume that they are the same, even though it may slightly underestimate CP)5 varied between 75-97% of HRmax. In fact, the variation was so large that whilst some participants were still exercising in the moderate domain, others were suffering in the severe domain, even though they were exercising at the same relative intensity with respect to HRmax. Also, sex-based differences were found suggesting that women systematically have higher thresholds than men relative to their HRmax. If this was not enough, heart rate can vary on a daily basis within the same individual depending on factors such as ambient temperature, hydration status, and altitude.6,7,8 Hopefully, it is now evidently clear, that exercise prescription based on heart rate comes with several inherent issues making it difficult to accurately prescribe intensity.

The talk-test

The question then remains, can these exercise zones be determined without the need for advanced laboratory equipment? It seems that way. In a study by Woltmann et al.,9 they sought to understand how the ability to talk interacted with the physiological responses to exercise, and thereby the intensity thresholds. Sixteen young adults were recruited as subjects and underwent several tests on a motorised treadmill. First, their LT, CS (again, CS was not used but instead respiratory compensation point, which we will assume is the same)5, and VO2max were determined from the expired air during a ramp incremental test where the participants ran on a treadmill where the speed increased by 0.5 mph every two minutes until volitional exhaustion. During the second test, they followed the same ramp protocol and after 1.5 minutes on every level, they were asked to recite the Pledge of Allegiance (yes, this study was done in the US) and were subsequently asked the question “Can you speak comfortably?”, the subjects’ responses were clamped to:

  1. Yes, I can speak comfortably.
  2. Yes, I can speak, but not entirely comfortably.
  3. No, I cannot speak comfortably.

The fastest speed that the subjects stated that they were able to speak comfortably was termed last positive, the first speed they were able to speak but not comfortably was termed equivocal, and the first speed at which they were unable to speak was called negative. From this, the subjects ran three 30 minutes bouts (or until volitional fatigue) at the previously determined speeds and they were once again asked to recite the Pledge of Allegiance to do the talk test. RPE, HR, and blood lactate levels were also measured.

In the first trial, last positive, the subjects’ RPE, HR, and blood lactate remained steady throughout the entire trial. That is, they exercised in the moderate domain below the lactate threshold. During the equivocal trial, which was only 0.5 mph faster than the previous, RPE and HR slowly increased throughout the trial whilst blood lactate doubled over the first 20 minutes and then remained steady. Altogether, this tells us that they were running in the heavy domain between LT and CS. Only 2/16 participants managed to complete the full negative trial Even though the speed was constant throughout, RPE approached 10/10, HR drifted towards 200 bpm, and the blood lactate kept increasing throughout – the subjects were exercising in the severe domain.

For how long do you need to talk then to accurately discriminate between the intensity zones? To answer this question, Schroeder et al.10 conducted a similar experiment as previously described but had their subjects recite a paragraph that was either 31, 62, or 93 words long, resulting in a speech duration of ~9, ~20, and ~28 seconds. The two shorter paragraphs slightly overestimated both thresholds whilst the 93-word paragraph accurately predicted both. From this, it seems like a speech duration approaching 30s is ideal to accurately assess the working intensity. However, this may only be relevant at intensities around the LT and CP/CS as speech will instantly be difficult to produce at intensities >>CP/CS and will not be disturbed at all <<LT.

The physiology underlying the talk-test

Clearly, the most important purpose of breathing is to facilitate respiratory gas exchange, but it is also involved in speech production. It must be noted that the underlying mechanisms that drive breathing during exercise are not fully understood, but is in large determined by the proportion of CO2 in the arterial blood.11 To speak when exercising, one must reduce their breathing frequency causing a suppressed total ventilation. This means that the amount of cleared CO2 is reduced.12 Consequently, the CO2 content in the arterial blood becomes elevated which lowers the blood pH. As previously mentioned, this is a signal to increase ventilation. Thereby, discomfort during speech at higher exercise intensities are likely caused by the insufficient CO2 clearance secondary to a reduced ventilation. During exercise, total ventilation does not increase linearly to exercise intensity. Instead, at the LT and CP/CS disproportional increments of ventilation occurs secondary to the increased metabolite accumulation from additional sources such as lactate production.13,14 These sudden needs for additional ventilation is the reason why the talk test works – around the LT and CS, small elevations in work-rate result in larger increments in the drive for ventilation whereupon the ability to speak comfortably is reduced.

Summary

Whilst the talk-test has been proven to be a valid and reliable method to approximate intensity zones for a multitude of sports and populations,15 the mechanisms underlying it still remain somewhat speculative. Nevertheless, it is a highly convenient method to prescribe exercise intensity without the need for any extra equipment. Don’t have an exercise companion? Talk to yourself instead!

References
  1. Saini M, Kulandaivelan S, Devi P, Saini V. The talk test-A costless tool for exercise prescription in Indian cardiac rehabilitation. Indian Heart J. 2018;70 Suppl 3(Suppl 3):S466-S470. doi:10.1016/j.ihj.2018.09.009
  2. Burnley M, Jones AM. Oxygen uptake kinetics as a determinant of sports performance. European Journal of Sport Science. 2007;7(2):63-79. doi:10.1080/17461390701456148
  3. Jamnick NA, Pettitt RW, Granata C, Pyne DB, Bishop DJ. An Examination and Critique of Current Methods to Determine Exercise Intensity. Sports Med. 2020;50(10):1729-1756. doi:10.1007/s40279-020-01322-8
  4. Iannetta D, Inglis EC, Mattu AT, et al. A Critical Evaluation of Current Methods for Exercise Prescription in Women and Men. Med Sci Sports Exerc. 2020;52(2):466-473. doi:10.1249/MSS.0000000000002147
  5. Galán-Rioja MÁ, González-Mohíno F, Poole DC, González-Ravé JM. Relative Proximity of Critical Power and Metabolic/Ventilatory Thresholds: Systematic Review and Meta-Analysis. Sports Med. 2020;50(10):1771-1783. doi:10.1007/s40279-020-01314-8
  6. Wingo JE. Exercise intensity prescription during heat stress: A brief review. Scand J Med Sci Sports. 2015;25 Suppl 1:90-95. doi:10.1111/sms.12381
  7. Dion T, Savoie FA, Asselin A, Gariepy C, Goulet ED. Half-marathon running performance is not improved by a rate of fluid intake above that dictated by thirst sensation in trained distance runners. Eur J Appl Physiol. 2013;113(12):3011-3020. doi:10.1007/s00421-013-2730-8
  8. Mazzeo RS. Physiological responses to exercise at altitude : an update. Sports Med. 2008;38(1):1-8. doi:10.2165/00007256-200838010-00001
  9. Woltmann ML, Foster C, Porcari JP, et al. Evidence that the talk test can be used to regulate exercise intensity. J Strength Cond Res. 2015;29(5):1248-1254. doi:10.1519/JSC.0000000000000811
  10. Schroeder, M.M., Foster, C., Porcari, J., & Mikat, R. EFFECTS OF SPEECH PASSAGE LENGTH ON ACCURACY OF PREDICTING METABOLIC THRESHOLDS USING THE TALK TEST. Kinesiology. 2017;49:9-14.doi:10.26582/K.49.1.14
  11. Forster HV, Haouzi P, Dempsey JA. Control of breathing during exercise. Compr Physiol. 2012;2(1):743-777. doi:10.1002/cphy.c100045
  12. Creemers N, Foster C, Porcari JP, Cress ML, de Koning JJ. THE PHYSIOLOGICAL MECHANISM BEHIND THE TALK TEST. Kinesiology. 2017;49(1):3-8. doi: 10.26582/k.49.1.15
  13. Skinner JS, McLellan TM. The transition from aerobic to anaerobic metabolism [published correction appears in Res Q Exerc Sport. 2013 Jun;84(2):273. McLellan, T H [corrected to McLellan, T M]]. Res Q Exerc Sport. 1980;51(1):234-248. doi:10.1080/02701367.1980.10609285
  14. Carey DG, Pliego GJ, Rohwer JL. The ventilatory response to incremental exercise: is it one or two breakpoints?. J Strength Cond Res. 2010;24(10):2840-2845. doi:10.1519/JSC.0b013e3181e2734a
  15. Foster C, Porcari JP, Ault S, Doro K, Dubiel J, Engen M, Kolman D, Xiong S. Exercise prescription when there is no exercise test: the talk test. Kinesiology. 2018;50(1):33-48.

Photo by Brian Erickson on Unsplash

Updated on May 30th

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