The Rating of Perceived Exertion (RPE) has long been encouraged for use in the group exercise setting in addition to heart rate checks. But in recent years, it has increasingly become the primary means for determining how hard you are working. Considering the margin of errors and the time required to explain and take heart rate checks, instructors have gradually eliminated stopping at the peak of class to do a pulse check. It has also become the primary means of measuring exercise effort in exercise video workouts.
In 1982, Gunnar Borg developed a scale for monitoring intensity based on how hard you feel you are working.
The original Borg scale ranged from 6 to 20:
6 to 11 (very,very light) – essentially the range for warm-up and cool-down
12 to 13 (somewhat hard) approximately 60% MHR
16 (between hard and very, hard) – approximately 90%
(Pollock, Wilmore and Fox 1984 ).
In 1986, the American College of Sports Medicine revised it to a scale of 0 to 10 with zero being “nothing” and 10 being “very, very heavy – almost max”. (Source- ACE Instructor Manual)
0 Nothing at all
0.5 Very, very weak
1 Very weak
4 Somewhat strong
7 Very strong
10 Very, very strong
Source: Borg, G.V. (1982) Psychological basis of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377-381. American College of Sports Medicine
With this version of the modified Borg Scale, to be working in your aerobic or training zone, you would want to rate your effort between 3 and 7. If intensity or interval training’s your goal, you would push up to and beyond 8 during the work efforts.
In some classes or other situations, the scale may be even further modified to a 1 to 5: 1 being nothing, 2 light, 3 moderate, 4 hard, and 5 very hard.
Reebok University made an attempt to further simplify it with Effort Scales for cardio vascular training using a 1 to 4 scale – (2012 update: this scale never really took hold in application)
Exertion Level 1 – Light to moderate effort. Mild increase in breathing rate.
Exertion Level 2 - Moderate effort. Noticeable increase in breathing.
Exertion Level 3 – Moderate to hard effort. Noticeable increase in depth/rate breathing. Difficulty talking in full sentences.
Exertion Level 4 – Hard to extremely hard effort. Unable to talk at all. Gasping slightly for breath.
While the RPE scale is considered to be fairly reliable as a means to measure intensity, approximately 10% of the population tends to over or under rate their exertion (Morgan 1981). Therefore it was not encouraged to be used as the sole means for determining exercise intensity.
The “Talk Test”
During an “aerobic” exercise session, one should be able to carry on a somewhat stilted conversation, if you are indeed “with oxygen” – which is what the word “aerobic” means.
If you are gasping for air and unable to talk, you are most likely working at or beyond the anaerobic “without oxygen” threshold – a very, very, very hard intensity level at or beyond at the high end of their aerobic zone.
If you can sing the entire Star Spangled Banner and hit the high note with ease – you are probably not exerting much effort – and you have a great musical range! If you can sing Row Row Row your Boat, but have to take a breath after every other word, then you are probably working pretty hard!
While these methods of reading intensity level are subjective, they tend to be good ways to help participants judge and adjust their level of exertion according to their fitness goals.
Furthermore, with improved fitness level, the resting heart will change to reflect the improvement – using the Karvonen formula, one would need to refigure resting heart rate after a period of time to recalculate their target heart rate. But with perceived exertion, as their body adapts to the challenges, they will tend to judge their level accordingly.
Although these 2 methods tend to be more practical and time efficient for group fitness settings, it is still the current recommendation to use a variety of methods – including target heart rate checks – to monitor exercise intensity.
While some insight has been offered relevant to the decreased practice of the use of target heart rate checks in group exercise, it is not to be implied that using this standard of measurement is ineffective or inappropriate. The reality is that instructors tend to be pre-occupied with all the other details of teaching a class and, over the years, heart rate monitoring has become less of a priority, primarily due to time restraints.
If you are taking classes where exercise intensity is not measured, you are unsure of how hard you really are working, you have a medical reason for knowing your target heart rate range and how hard you’re working, or if you simply need incentive to push a little harder, let your instructor know about your needs.
Your other option is to get a heart rate monitor and let it give you the feedback needed to work appropriate to your fitness goals.