The RPE scale

The RPE scale ranges from 6 to 20*, and includes a literal description for each level of exercise intensity. It was designed so adding a 0 to the level of exertion would give a rough estimate of your heart rate i.e. if you were resting (a 6 on the scale) your heart rate would be in the neighborhood of 60. Although RPE isn’t accurate enough for detailed physiologic studies, research has demonstrated an amazingly high correlation for any individual from day to day. In other words if you felt you were exercising at a 13 (somewhat hard) on two different days, and checked your heart rate, it would be quite similar.

How can you use the RPE scale? First familiarize yourself with the levels. Then, using a treadmill or wind trainer, rate your own level of exertion BEFORE you check your pulse rate. With a little practice you will find that you will be amazingly accurate in predicting your heart rate. At that point you can use your own RPE instead of a heart rate monitor to monitor the intensity of the day’s workout.

In addition,

- Learn during interval training. Use a heart monitor that calculates average HR. See how much intensity you can maintain for various durations. Focus on how these effort levels feel. Then compare your perceived exertion to your average HR.
- Learn on group rides. Note how the adrenaline from towing a group makes you sometimes exceed a pace you can sustain.
- Learn in time trials. Notice how you almost always go faster in the first third of the race than you can sustain in the final third. Find your own "sweet spot" of effort that's sustainable for about an hour.

RPE can change as fitness improves and with factors such as hydration, carbohydrate status, and ambient temperature. So recalibrate your own RPE scale regularly during the season if you are using this tool in your training. A heart rate monitor or a watts meter are important tools. But when it matters most, your carefully honed self-perceived exertion level is still the best monitor ever created.

* RPE scale
6 - resting
7 - very, very light
9 - very light
11 - fairly light
13 - somewhat hard
15 - hard
17 - very hard
19 - very, very hard

Training using PE
Found on Roadbikerider.com:

Question: I want to improve my power at lactate threshold (LT) so I can excel in time trials and on long climbs. But I don't know how hard to ride during LT training. Lab tests are expensive, I'm told that heart rate is unreliable and I don't have a watts meter. Is there a simple method for nailing LT intensity without all the black magic?

Answer: LT can be gauged by wattage, lactate accumulation, heart rate or perceived exertion. The first requires a relatively expensive power meter as well as a lab test to find your wattage at LT. Actually measuring lactate means periodic blood draws -- not too practical while you're riding the road. And heart rate can vary for a given power output due to hydration status, environmental conditions and other factors.

That leaves your personal rating of perceived exertion (RPE). In other words, how hard you feel like you're riding. In the old days, everyone trained with RPE. Before heart monitors there was no other way. The good news is that research shows RPE is an effective way to determine intensity.

Allen Lim did ground-breaking research on cycling power while working on his Ph.D. in exercise physiology at the University of Colorado. In an e-mail he wrote:"Training prescriptions don't need to be overly complicated. If athletes are in tune with themselves and quite experienced at perceiving effort, then what they perceive as hard can be used consistently as a reference point for training-induced adaptations and for determining training pace."

So, if your workout calls for a 20-minute effort at close to your LT, it's fine to forget the technology and simply ride at an intensity that feels hard. You'll be close to your lab determined ideal intensity.

How hard is hard? Think of effort on a scale of 1 (lying on the couch) to 10 (riding flat-out and suffering). On this simplified RPE scale, LT intensity is between 8 and 9. This is the point at which breathing is at the breakpoint between hard but steady and labored with gasping. Another way to find it: Increase intensity until you begin to gasp, then back off a notch.

Lactate Threshhold

Recent work has focused on the blood lactate threshold (LT) as a reflection of an individual's level of training. The lactate threshold is that % of VO2 max. at which the cardiovascular system can no longer provide adequate oxygen for all the exercising muscle cells and lactic acid starts to accumulate in those muscle cells (and subsequently in the blood as well). At high levels of activity (but below 100% VO@max), there are always a few muscle cells (not entire muscles, but a small number of cells within those muscles) that are relatively deficient in oxygen and thus producing lactic acid. But this lactic acid is quickly metabolized by other cells that are still operating on an aerobic level. At some point, however, the balance between production of lactic acid and its removal shifts towards accumulation. This point is the LT. It is usually slightly below 100% VO2 max., and will improve with training (move closer to 100% VO2max). Those with an increased LT not only experience less physical deterioration in muscle cell performance for any level of %VO2max, but also use less glycogen for ATP production at any level of performance. Thus an improvement in LT allows the individual to perform at maximal levels for a longer period of time before running out of adequate energy (glycogen) stores.