The Borg Scale: how accurately does it measure an athlete's training intensity?

How Valid Is the Borg Scale?

The Borg Scale is a simple rating of perceived exertion (RPE) used by many coaches and physiologists to assess an athlete’s level of intensity during training or testing sessions. For readers unfamiliar with the RPE scales, there are two common types: the 15-point scale (6-20, and the nine-point scale (1-10). Less commonly used are the 21-point scale (0-20) and criterion-ratio scale (10 or 20-point).

The 15-point scale is illustrated below as an example: point 6 would be the equivalent of sitting down doing nothing, 9 would be walking gently, 13 a steady exercising pace and 19/20 the hardest exercise you have ever done.

6
7 - Very, very light
8
9 - Very light
10
11 - Fairly light
12
13 - Moderately hard
14
15 - Hard
16
17 - Very hard
18
19 - Very, very hard
20 - Exhaustion

In a recently-published study, a team of Californian researchers set out to test the different types of Borg scale to establish whether they were a valid measure of exercise intensity. They did this by carrying out a meta-analysis of many previous studies which had compared RPE scores with physiological measures of intensity, such as lactate levels, heart rate and VO2.

A total of 64 studies were collated for analysis, examining correlations between RPE and one or more of the following physiological variables: heart rate, lactate concentration, %VO2max, VO2, ventilation and respiration rates.

The researchers’ key findings were as follows:

  1. The RPE scales did correlate with heart rates, although studies using sedentary subjects showed weaker correlations than those using trained subjects;
  2. The scales also correlated with blood lactate levels, although the category ratio and 9-point scales showed stronger correlations than the 15-point scale, and male RPE scores showed weaker correlations than female scores;
  3. The scales correlated strongly with %VO2max, with no significant variations between sex, subject, exercise or scale types. Interestingly, RPE scores were also related to VO2, but with variations according to sex and exercise type, the correlation being strongest with males and cycling;
  4. Ventilation and respiration rates were strongly correlated with RPE scores, particularly for males;
  5. Other variables, such as exercise protocol (intermittent versus continuous) and RPE mode (whether the subject estimated RPE from the response to exercise or produced the exercise level from the RPE value given in advance) also altered the strength of the association between RPE scores and physiology.

So it seems that, while there is an overall correlation between RPE scores and physiological criteria, there is a degree of inconsistency and different variables can affect the validity of the RPE score as a measure of exercise intensity.

The researchers conclude that the RPE scales are most valid when they involve male subjects working hard and that the 15-point scale is best. They also conclude that, while heart rates, lactate and VO2 can vary within individuals from session to session or race to race, breathing rates (respiration) are a more reliable reflection of exercise intensity.

In conclusion, this study supports the use of RPE scores as a means of assessing exercise effort, with the proviso that certain situations or subjects may lessen their validity.

Journal of Sports Sciences, 2002, 20, 873-899

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