Measuring Intensity Series, Part 1: Rating of Perceived Exertion
What is RPE and how can you use it to supplement your measure of intensity?
When exercising, the FITT principle dictates we must consider the Frequency, Intensity, Time and Type of exercise being performed. When developing fitness, the two most important factors are Time and Intensity. When measuring intensity we have a few options. Most often, one will see plans based on pace or heart rate, but power is becoming more popular, recently. A measure of intensity we don’t see super often, but is a really great adjunct to the others, is Rating of Perceived Exertion, or RPE.
RPE or your “Rating of Perceived Exertion” is a subjective measure of how hard you are working. This is indicated by the “Perceived” portion of the name; what is your perception of your effort? For example, you and a training partner may be running the same pace at the same heart rate, but it feels “moderate” for you and “hard” for your training partner.
You might be thinking, “Well, what’s the use in that? Don’t I want objective data to tell me how hard I’m working?” That is partially correct. We do want objective numbers (heart rate, pace, power) that give an indication of how hard we are working, relative to a given anchor point (maximum heart rate, functional threshold power, velocity at VO2max, etc). BUT, those numbers only tell part of the story. Working at 80% of FTP might feel “hard” some days and “moderate” other days and possibly even “easy” while tapering. To paint a clearer picture of a workout, it’s best to use a mix of subjective (how you feel) and objective (how hard you’re working) measures.
“But, if this whole thing is subjective, how does one achieve consistency?” Through practice! Every workout, take periodic checks and ask yourself, “How hard does this feel? Does the ‘easy’ effort prescribed actually feel easy? Or do I feel like I’m working kind of hard?” Over time, you will develop an intuition for how hard you are working. You may do this by assessing things like posture (“Are my shoulders drooping?”), breathing (“Is my breathing labored?”) or fatigue (“Are my legs heavy?”). The more you practice assigning an RPE value to your effort, the more consistent you will become in estimating your effort by feel. And that’s one of the major reasons I like RPE as an adjunct to objective measures; by its nature, it encourages one to become introspective during an effort.
“Okay, this sounds great and all, but what do you mean, when you say ‘assign an RPE value’? Like, where do these magic numbers come from?” That’s a great question! There are a number of RPE scales out there. If you Google it, you’ll most likely get a 10-point scale:
Classic 1-10 scale
Or the Borg RPE scale:
Borg RPE scale
You’re probably asking yourself, “Six to 20? Why on Earth would someone use 6 to 20?” I know I did the first time I saw this thing.
Me, the first time I saw the Borg scale
Turns out, there was a method to this mayhem. Dr. Gunnar Borg, Ph.D., MD, a psychiatrist from Sweden, developed this scale in the 1960’s. The idea being, if you multiply each number by 10, it would correlate to a heart rate at that RPE. In other words, a person working at 150 bpm would report an RPE around 15. While this might hold true for a percentage of the population, the heart rate thing is more of a “fun fact” than a “tried and true” correlation.
The main point to consider is that an RPE scale can come in many forms. Here are a few I’ve seen used in the past:
A two-category scale:
Easy
Hard
That’s it. May work with very polarized training, but we tend to work in more varied intensity ranges than just ‘hard’ or ‘easy’.
A three-category scale. “General Running Endurance” (GRE) intensities are defined as:
GRE I: Easy running. Recovery runs.
GRE II: Moderate running. Aerobic training. Around half marathon or marathon pace.
GRE III: Hard running. Anything from threshold work to longer reps on the track or VO2 work.
A four-category scale:
1. Easy: Recovery runs
2. Aerobic: Long runs
3. Threshold: Tempo runs
4. Anaerobic: Speed work
A five-category scale based mostly on breathing
1: Light running. Can speak full sentences. Breathing is a little deeper and a little more frequent than resting.
2: Moderate running. Can still speak in full sentences. Breaths are becoming deeper, but not much more frequent.
3: Threshold running. Can get out a few words at a time. Breaths are becoming deep and frequent.
4: VO2 running. One word at a time. Breathing is labored. Deep, fast breathing.
5: Anaerobic Reps: Unable to speak; maybe a word at a time. Struggling to breathe. Breaths are very frequent and shallow.
Personally, I tend to use a four or five category classification. I find it a bit easier to identify shifts in effort as one increases intensity. In our programs, we tend to use a 10-point scale, mostly because this is easy to conceptualize for most people; 1 is easy, 10 is hard.
Okay, so you’ve decided to use a 1-10 RPE scale. How does one use it in practice? Well, if someone is new to running, or doesn’t have a heart rate monitor, I will often let RPE guide the workout. Take the Cooper 12 Minute Run Test, used to assess fitness at the start of a program, but guided by RPE.
Ramp up in 4 steps
400 m @ 3-5 RPE
400 m @ 4-6 RPE
400 m @ 5-7 RPE
400 m @ 6-8 RPE
Walking Recovery
3 min @ 1-2 RPE
Get to start lineRepeat 4 times
Hard
100 m @ 7-10 RPEEasy
1:30 @ 1-2 RPEActive
12 min @ 7-9 RPE
Aim for consistency!Cool Down
400 m @ 1-2 RPE
Again, if someone is new to running, this is going to be a bit of a guessing game to start with. But after a workout like this, where an athlete runs through a variety of intensities, they should have a very good starting point to start applying RPE to their daily running.
While objective metrics like heart rate, pace, and power have their place, RPE offers a unique insight into the subjective side of your workout experience. It's the bridge between the numbers and your effort.
By incorporating RPE into your fitness routine, you can fine-tune your training and prevent overtraining by listening to your body and making adjustments accordingly. Remember, our bodies don't always adhere to a strict numerical code. Some days, an 80% effort might feel harder than other days. With RPE, you can adapt and ensure that every workout aligns with your current fitness.
So, start incorporating RPE into your training sessions. Pay attention to how your body feels during workouts, and assess your effort on a scale of 1 to 10. Over time, you'll develop an intuitive understanding of your exertion. With RPE, you'll be able to train more effectively, reduce the risk of overtraining, and ultimately make more significant strides towards your fitness goals. Your body will thank you for it.
Fitness Assessment Series: Cooper
Run as far as you can, not as hard as you can.
Part 1: The Cooper 12 Minute Run Test
A (very) brief History
The Cooper 12-minute Run was initially developed by Dr. Kenneth H. Cooper in 1698 as a way to assess the cardiovascular fitness of soldiers in the US military. This was a very convenient way of assessing a large group of people all at once.
Categorizations could be made based on the distance traveled, in meters.
Normative Data
There are a few normative tables out there, for male and female subjects. However, I will not be delving into that data in this post for a few reasons…
The original tables were created by Cooper in 1968. As of this writing, that’s 55 years ago! A lot has changed in the world of exercise physiology since then.
As I mentioned, there a number of tables out there. Over the course of 55 years, the 12-minute run test has been studied quite a bit. And some of those studies aim to create more normative data. The main issue is each new table is specific to the population studied. For example, Cooper’s original table was created using data from military subjects who, at the time, were primarily healthy males in their 20’s and 30’s. So, that could reasonably be a good reference for healthy males in their 20’s and 30’s, but probably not a 45 year old female, trying to get in shape for her next half marathon.
Lastly, (and more importantly) I don’t really see the benefit of classifying oneself into “Good”, “Better”, “Best” categories, outside of bragging rights and feel-good-ery.
The objective of self-assessments are to get a snapshot of your fitness on that day, recognize trends over time, and make adjustments as necessary. Not compare yourself to the collective faceless blob of individuals some researcher amalgamated into a “normative data” chart. The only person you should compare yourself to is you. And, maybe, your running club frenemy. You know, that one person who is a similar height, weight and fitness. The one you beat in local races sometimes, but they also beat you sometimes. So, you train together, do your long runs together, talk about life, and become best friends. But when it comes to race day, they’re your mortal enemy. Mine is/was Ben. You don’t have one of those? Oh...maybe it’s just me, then.
How to do a 12 Minute Run Test
The 12-minute run is best-done on an outdoor track. Although, with GPS and footpod technology where it is today, one could reasonably perform this assessment just about anywhere they could find a relatively flat, uninterrupted stretch of running surface. After a thorough warm-up, (easy running, dynamic stretching, strides, etc.), one simply runs as far as they can in 12 minutes.
Pacing is important, here. Notice, the instructions say “run as far as you can,” not as hard as you can. Don’t just line up on the start line, press the lap button on your watch and sprint the first 400 meters, hoping to “bank” time on the front end which will “make up” for the time loss on the back end. Having some idea of a goal pace and running as evenly as possible over course of the assessment will yield the best result.
Of course, this will be a challenge for those doing this assessment the first time, but will be much easier after the first assessment. After a training block (6-8 weeks), you can look back at your previous assessment, review recent workouts and make a fairly good estimate of a do-able pace. Personally, as long as I have been performing a variety of workouts (including aerobic, threshold and VO2 work) I tend to aim for a 3% - 5% improvement from assessment to assessment.
A sample workout might look something like this:
Warmup 1: 4 laps around the track
Start nice and easy, make each lap a little faster than the last
Last lap should be around 85% to 90% of a maximum 400m effort
Take a 3 minute walking break
Warmup 2: 6 x 100m strides with 1:30 rest between
Remember, strides are fast, not hard
Spend the first 30 meters ramping up, 40 meters maintaining, 30 meters ramping down
Doesn’t have to be perfect, but should feel smooth
Take an extra 1:30 rest after the last stride
Main set: 12 Minute Run Test
Again, try to stick to an even pace.
The first 400 - 600 meters should feel quick, but relatively easy. Don’t chase the fatigue; let the fatigue come to you.
If you’re breathing is already labored after the first 400 - 600 meters, you may going out too quick.
Cool down: Jog lightly for 5 minutes, walk for 5 minutes
Post-Assessment Analysis
Okay, so you spent some time delving through your training journal, devising the perfect pacing strategy. You go to your local track. You warm up with your progression, dynamic stretches and/or strides. You line up on the start line, press the lap button and promptly sprint the first 400 meters thinking to yourself, “Wow! I feel great!” You come through the first lap 10 seconds under your planned pace, “Welp, that was a little fast. At least I have 10 seconds in the bank, now!”
Fast forward 5-6 laps; you’re tanking. Your palms are sweaty, knees weak, arms are heavy. There’s vomit on your singlet already, mom’s spaghetti. You’re thinking to yourself, “Come on! Just a little further!” until your watch finally bellows that beautiful *beep* you’ve been waiting for, allowing you a much-deserved respite. Twelve minutes done. And only 20 seconds per mile slower than you had planned! Great! Now what?
Look at the distance you’ve gone. Is it more, less, or the same as last time you’ve performed this assessment? If it’s about 3% - 5% more, great! Your fitness is improving! If it’s about the same, or less, review your training journal and look for gaps. Are you missing aerobic volume? Do you need to incorporate more threshold or VO2 work? (This is where a coach can come in really handy.)
To be as accurate as possible, one could theoretically bring a measuring wheel to the track, mark their finishing spot and measure the exact distance, like a psychopath. But I got tired of bringing my measuring wheel every time I wanted to perform a 12-minute run. And as I mentioned previously, the accuracy of GPS and footpod technology is adequate to simply use the number spit out by your watch. Personally, I use my Stryd footpod to provide speed/pace data, instead of GPS. I started doing this because my Garmin isn’t the greatest in tree cover, and liked the result so much, I just do it for every run, now.
How else can I use this data?
The really great thing about assessment runs, is the DATA. They are an excellent opportunity to update metrics for subsequent training blocks. So, what do I look at when I analyze a 12-minute run test? First, let’s take a general overview of the 12 minute portion and it’s data:
Fig 1. Complete Work Rep
Fig 2. Compete Work Rep Stats
Well, first impression; the heart rate plateaued around 180 bpm (with a peak of 184 around the 6:00 mark) and there’s a fair amount of drift in pace and power over the course of the rep. In other words, I was unable to produce any additional output (pace/power) for the given input (heart rate). Which indicates I was working at (or near) my maximal aerobic ability. But how much did my pace and HR drift? Let’s compare the first half and second half (you can click the images to make them larger).
Over the first half of the rep, I was able to cover 0.86 miles in the first 6:00, yielding a 7:00/mile pace (3.84 m/s) with an average power of 359 W.
Over the second half of the rep, I was able to cover 0.79 miles in the first 6:00, yielding a 7:36/mile pace (3.53 m/s) with an average power of 342 W.
In other words, my speed declined by about 8% and my power declined by close to 5%. To put it bluntly, I did not pace myself very well. I generally consider anything less than about 3% drift to be an even split. This was a big time positive split. But, some valuable information can still be gleaned from this data and used in training.
First, a note on VO2max: Most moderately trained individuals can maintain their VO2max pace for approximately 10 minutes. Meaning, for this test, it’s safe to assume one will be running at, or slightly under their VO2max pace (vVO2).
And a note on lactate threshold (LT): A useful rule of thumb is LT typically occurs around 85% vVO2 and (in my experience) LT heart rate occurs around 90% VO2max HR. So, what can I use from this assessment?
I use the average HR over the second half of the rep to estimate a LT heart rate: 181*0.90 = 163 bpm. (Since HR takes a bit to plateau, it tends to drag the average of the first half down. So, I’ve found the second half average to be more indicative of the actual effort put forth.)
I use the average pace over the entire rep to estimate a LT pace: 7:16/mi *0.85 = 8:33/mi.
Now, I can run VO2max workouts by pace (which I would typically do on a track, anyway) or I can run threshold workouts at either an 8:33/mi pace or 163 bpm.
Note that, with reassessments, you may not notice your average HR changing very much. In fact, if you are getting fitter and/or pacing yourself better, your average HR might actually decrease a few beats over time. But that’s okay; if you’re still covering more distance in the same amount of time and the same (or lower) heart rate, you are becoming a more efficient runner.
Sometimes, I use an efficiency factor to track progress. It takes pace and HR into account and looks something like this:
Eq 1. Efficiency Factor
Now, I know what you’re thinking, “Meters per second? Who uses meters per second? And why is it multiplied by 60?”
Professionals. That’s who uses meters per second. And the 60 comes into play with the unit conversion like so:
Fig 7. How’d I get there?
Dividing meters/second by beats/minute is equivalent to multiplying meters/second and minute/beats. And we can replace the minute in minute/beats with 60 seconds so the seconds cancel each other out.
Technically, this gives the Efficiency Factor a unit of “meters/beats” which kind of makes sense; you want to travel as far as possible for any given heart rate. In other words, as meters goes up OR beats goes down, efficiency goes up! I don’t get too wrapped up in the efficiency factor for any given assessment, it’s just another tool to ‘normalize’ and compare two similar efforts and determine if progress is being made.
Wrap Up
Welp, if you made it this far, thank you for reading! My main goal is to provide practical information for anyone looking to assess themselves and improve in their sport. After all, you can’t improve what you can’t measure. I hope you found something useful in this post. And as mentioned in the title, this is the first in a series of posts dedicated to assessing fitness. I also plan on covering the 30 minute time trial, the 9/3 assessment, VDOT scores and useful data derived from race results (5k and 10k), so stay tuned!
Thank you again, and happy running!