Knowing your limits: it’s good to talk!

Is technology essential to monitor training intensity and lactate thresholds? Sports Performance Bulletin looks at some recent research suggesting a much simpler and easier method could be equally effective

Knowing your exact training intensity is important for a number of reasons the most important of which is training specificity. In short, adjusting your training intensity allows you to target specific energy requirements of your sport. You can find a more in-depth discussion of training intensities/zones in this Sports Performance Bulletin article. For endurance athletes, two key training intensities are the ‘ventilatory threshold’ (VT) and ‘respiratory compensation threshold’ (RCT).

In a nutshell, VT represents the intensity at which ventilation starts to increase in a non-linear fashion. This is often accompanied by a rise in blood lactate. RCT meanwhile (sometimes referred to as ‘VT2’) represents the (higher) intensity at which the ventilation rate increases further and lactate begins to steadily accumulate. In a nutshell, you can sustain your aerobic training intensity at VT but at RCT, the increasing accumulation of lactate will, at some point, force you to slow down or stop.

The problem with technology

Knowing your lactate thresholds can be very useful for tailoring your work intensity. The problem however is that accurate testing to determine these thresholds can be time consuming and expensive. The technology for measuring actual blood lactate levels outside of a laboratory environment is still in its infancy; nearly all lactate measurement devices require an actual blood sample to be taken on a swab or stick, which then has to be inserted into the device – try doing that in the middle of a run or bike session! To complicate matters further, these thresholds aren’t fixed – they can easily change as your fitness increases or declines – which means that you cannot rely on simply maintaining a given power output or speed to ensure you’re working at the right intensity.

Non-invasive measurement

Is there any way to determine your blood lactate levels without the use of invasive, expensive or impractical technology? Well, some fairly recent research by Spanish and US scientists suggests that there could indeed be a much simpler, cheaper and faster way to reliably determine these thresholds.

In one study, conducted by scientists at Institute of Biomedicine (IBIOMED) in Spain, eighteen highly-trained cyclists underwent two incremental tests(1). One test included lab measurements of respiratory gas exchange to accurately determinate the ventilatory (VT) and respiratory compensation (RCT) thresholds. On a separate day, a ‘talk test’ was performed using the same exercise protocol. During this talk test, the subjects read a standard paragraph at the end of each incremental stage. The first stage at which each cyclist could not talk comfortably was noted by the researchers (TT1). The next stage of exercise intensity that the researchers noted was when the cyclists could definitely not talk (TT2). The scientists then analysed the data to see if and how the cyclists’ VT and RCT were related to TT1 and TT2.

The key finding was that TT1 and TT2 were extremely closely related to VT and RCT respectively. In fact, there were no significant differences in workload, heart rate, lactate and rating of perceived exertion between VT and TT1. The same close relationship was also observed between RCT and TT2. In plain English, at the exercise intensity of TT1, each cyclist’s blood lactate, heart rate and power output was the same as when they exercised at VT and the same was true for TT2 and RCP – effectively eliminating the need for technology to identify these two intensity thresholds!

More evidence for the talk test

In a completely separate study three years later carried out by US scientists at the University of New Mexico, researchers sought to establish how effective a talk test carried out during a time trial was in identifying VT in highly trained cyclists(2). To begin with, a maximal graded exercise test was used to identify VT, maximal aerobic capacity and maximal heart rate in the cyclists using conventional measurement protocols. Then on a separate visit, the cyclists undertook an exercise trial in which the intensity was steadily ramped up.

During the trial, the participants were continually asked if they could speak comfortably after a standard passage recitation. Response options were:

  • *Yes
  • *I’m not sure
  • *No

The point at which each cyclist’s response changed from ‘yes’ to ‘I’m not sure’ or ‘no’ was then noted and compared with the data obtained during the conventionally-measured graded trial. The results once again showed that using the talk test was equally as effective at identifying VT as using more conventional lab-based measures such as oxygen consumption (VO2). In short, the researchers found that when the athlete could no longer speak comfortably, he was exercising at or near his VT. They went on to conclude therefore that the talk test can provide a practical method to gauge exercise intensity in highly trained competitive cyclists and other athletes.

Practical implications for athletes

These studies eloquently demonstrate that in trained cyclists at least, it’s possible to get an accurate handle on your VT and RCT by using a simple talk test during training. And given that the same physiological principles apply, there’s no reason to think that this method can’t be applied to other athletes such as runners, swimmers, rowers etc. Another benefit of course is that since the use of TT1 and TT2 are accurately correlated to blood lactate levels, this test could be a convenient method of monitoring fitness changes over time – eg to see at what heart rate you reach your TT1 or TT2 (the lower the heart rate, the more efficiently your body is coping with lactate – a strong predictor of performance). Even better, the use of the talk test requires no fancy technology whatsoever, making it ideal for technophobes and/or those on a budget!


  1. J Strength Cond Res. 2013 Jul;27(7):1942-9
  2. J Strength Cond Res. 2015 Apr;29(4):894-8

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