Whenever the phrase “Training by Feel” is mentioned, a common concept that comes to mind is Relative Perceived Exertion or RPE. In essence, this is a means of quantifying the effort an individual puts out. Also known as the Borg Scale (see Table 1), this was initially developed by Dr. Gunmar Borg to document a patient’s exertion during tests such as the Bruce Protocol. Sports coaches and athletes later on adapted the scale to assess the intensity of training or competition. For sports like running, cycling, and triathlon, the Borg CR10 Scale, with a range of 1-10, is more common (see Table 2).
The scale ranges from 6 to 20 wherein 6 is the lowest intensity possible (no effort at all), while 20 is maximal. Dr. Borg also used these numbers as a simple way of estimating heart rate for the given effort. The number assigned to a particular intensity multiplied by 10 would supposedly yield the corresponding heart rate for it. The following table lists the relative efforts that are tied with the numbers on the scale.
Table 1. The Borg Scale of Perceived Exertion

Source: http://www.hsph.harvard.edu/nutritionsource/borg-scale/
Table 2. Rating of Perceived Exertion (RPE) Table

Source: http://www.topendsports.com/testing/rpe-intensity.htm
I must admit that I use the concept of RPE regularly in training and racing. Training by feel is an essential tool in any athlete’s arsenal. Knowing how to pace and attack segments along the course is truly an art form mastered by experienced athletes. However, there are a few points that one must take into consideration when adopting such an approach.
Going back to the Borg Scale, the rating and heart rate correspondence is not a good relationship. Having done more than a hundred lactate tests, I was able to study how varied HR values are to each individual. As with the 220-age formula, the Borg Rating x 10 is not an effective predictor of HR values for a given effort. For example, my HR at rest would be between 45-55bpm, this is 5-10bpm lower than what the Borg Scale predicts. On the other hand, an athlete of mine has a Threshold Heart rate of 185-190bpm. Based on the scale, her HR should only be between 150-160bpm; however, based on her performance and using precise testing, we saw that she could easily sustain such a high HR. These are a couple of examples of how individual HR is to each athlete.
Another pitfall of the concept of RPE is related to how an athlete performs based on his aerobic and anaerobic qualities. According to the book “The Science of Winning” by Jan Olbrecht, the primary “engine” an athlete uses skews his RPE significantly. Case in point, have you ever “hit the wall” trying to sustain an effort that you thought was sustainable (i.e. BONK)? Similarly, do you have a lot more left in the tank despite giving your best shot in a race? Olbrecht explains that aerobic or anaerobic tendencies mask our perception of the “redline” because of our body’s preference. For example, a sprinter, with a high anaerobic capacity will tend to overestimate what he can sustain for a 1hr time trial while a marathon runner will often underestimate his pace. This is due to the fact that they have different comfort zones that affect their notion of effort. This has been validated by my subjects during Lactate Threshold testing. Whilst pinpointing their Lactate Threshold range (close to Maximum Lactate Steady State or MLSS), I have found that different athletes give varying ranges between 7 and 9. The same biological marker (which has the same effect) may feel differently for each individual. People who aren’t used to running hard will have trouble maintaining their actual Threshold.
Finally, RPE may also vary for the same person from day to day because of factors such as fatigue, adrenaline, stress, or nutrition. A 5min/km pace today will definitely feel different if done after a long run. Since the Borg Scale is relative, adhering to such a concept can be tricky especially if extraneous stimuli aren’t taken into account. Simply put, RPE values are not etched in stone, hence, using it to objectively quantify a session, program, or race effort is not accurate especially without proper discernment.
Does this mean that training/racing by RPE should be avoided? Not at all! Primarily, it is a means of quantifying how an athlete feels more so than his work rate. To use RPE properly, it has to be qualified properly. First and foremost, RPE should be “fine-tuned” using other tools such as time trials, critical power tests, and lactate testing. By using real-world and scientific methodologies, the RPE scale becomes more precise. Furthermore, RPE should be tied with something that is more absolute such as power and pace. As I mentioned, RPE is more aligned with an athlete’s “input” or how much effort he puts in. However, to measure progress and effectively compare performance between sessions or races, RPE must be paired with an objective value (pace, speed, wattage) to offset factors such as fatigue and stress.
Going fast is more than just sucking it up and going hard. Intelligent training and racing is the key to success!