Monitoring heart rate is a good way to gauge the intensity of a workout. While power is the preferred method and is not subject to external variables the way heart rate is, learning to train with heart rate is a skill all instructors should master. The problem is that it, and the training zones to go along with heart rate, has been a source of confusion for a very long time in the indoor cycling world.
When using a heart rate monitor, we are measuring the body’s response to the demands of a workout. In order to make sense of the numbers on the monitor, we need training zones to define how hard the workout is. A benchmark is needed on which to base those zones.
The most common benchmark is maximum heart rate (MHR). Because pushing class participants to their maximum effort is not recommended for most people, the fitness industry has historically used formulas to estimate MHR. The primary formula used by fitness instructors, heart rate monitors, exercise equipment, and online calculations is 220 – age. There are others, but using any formula to determine maximum heart rate can be dramatically incorrect for individuals and leads to confusion among participants.
MHR is largely based on genetics and reveals little about the fitness of the individual. Knowing the theoretical maximum rate that your heart will beat tells you nothing about where your lactate threshold lies. Using maximum heart rate as a baseline for training zones is wrought with other issues as well. You can learn more in the article “The Myth of Max Heart Rate”), but suffice it to say there are few reputable endurance coaches who pay attention to MHR, and most exercise scientists tossed it long ago.
If Not Maximum Heart Rate, Then What?
Exercise scientists have found that lactate threshold (LT) is an excellent predictor of performance and is the most accurate marker on which to base training zones. In his excellent book Total Heart Rate Training, Joe Friel describes LT as the following:
Lactate threshold is the level of intensity at which you begin to redline. In other words, the effort above LT is so difficult that you find it difficult to continue. Your breathing is deep and forceful, you are about RPE 7, and you may experience a burning sensation in the working muscles. You can only maintain this level of effort for a few minutes up to an hour or so for a highly fit athlete. And the higher above LT the effort goes, the shorter the time it can be maintained.
Lactate threshold can vary widely as a percentage of max HR, anywhere from 70% to 92%. This wide variation is why it can be so confusing to participants. An instructor may ask the class to ride at an intensity of “85%” with a stated purpose of training at threshold, but for one rider it may be barely attainable for more than a few minutes, and for another rider, it may feel like a casual effort. On the other hand, if the class is instructed to ride at their LT, then everyone would be putting out the same amount of effort and receiving similar benefits.
Our challenge, therefore, is to guide our riders to find LT if we are to create training zones that are personalized to their own ability and fitness level.
Until recently, this hasn’t been as easy as it sounds.
Lactate Threshold Assessments
The only truly accurate method of assessing LT is when blood lactate is measured directly via a pinprick blood draw during a graded exercise test. This requires an experienced and certified tester and is usually done at physiology labs.
Another method is a metabolic assessment in which expired gasses are analyzed during a graded exercise test, requiring the participant to wear a mask as they exercise. These assessments can be expensive, are somewhat uncomfortable, and are not always readily available.
Lactate threshold can also be estimated via a field test, such as a graded maximal aerobic power test (MAP) or a 20-minute field test*. Field tests can produce a result that closely equates to one’s actual lactate threshold.
Field tests are the most effective and accurate way to set training zones for participants, for both heart rate and power, without the use of expensive equipment or exercise science labs. At the Indoor Cycling Association, we have several details profiles for how to conduct these assessments in your classes, complete with energetic playlists and tips on motivating riders.
However, it is important to note that these field tests are not for everyone. They are very physically challenging, especially the 20-minute test, and may not be possible for some riders, especially the less fit and older population.
There has to be an easier way!
The Talk Test
The good news is that there IS an easy way to estimate lactate threshold by performing an assessment known as a talk test, a graded exercise test where the intensity is gradually increased every 2 minutes until the rider reaches an RPE of 7, or “hard.” Heart rate, RPE, and (if desired) power are recorded every 2 minutes. At the end of each 2-minute stage, riders are asked to repeat a phrase out loud to assess their ability to talk at that level of exercise.
The goal of the test is to estimate ventilatory threshold (VT) which is slightly different than LT. However, since the two physiological markers occur at about the same intensity, by defining one, you can estimate the other.
Aside from establishing a benchmark for zones, one of the greatest benefits of the talk test is how it helps participants better understand the concept of perceived exertion. As they proceed through the stages of the assessment from easy to moderate to hard, they have to contemplate how their body is feeling, how their breath is affected, and whether they can talk or not. The lesson in physical awareness for students is priceless and may even be a “lightbulb moment” where the rider can more reliably reach the desired effort through the instructor’s use of RPE and verbal descriptions of what the intensity should feel like. This will undoubtedly make an instructor’s job of teaching with perceived exertion much easier.
Before we dive into how the talk test works, it’s important to understand the science behind ventilatory threshold.