The cognitive and perceptual sensory signals of intensity are constant and consciously processed and organized in the cerebral cortex. And while heart rate (HR) and to a degree, power training are effective training tools HR and power cannot be perceived. That is, athletes cannot solely rely upon these numbers to precisely obtain prescriptive intensity efforts.

On the other hand, intensity of effort is very accurately perceived through a complex array of sensory signals arising in part from respiratory, metabolism and within the muscles.

In 1960, Gunnar Borg developed the rating of perceived exertion (RPE) scale. This is a very well known system and frequently adapted method of measuring effort during physical work.

RPE is used conjunctively in many settings for clinical diagnostics, therapy and rehabilitation, training of athletes, research and testing exercise intensity at sports science laboratories.

My first introduction in a clinical setting to this innovative intensity assessment protocol was at the Olympic Training Center as my role as USA Triathlon head coach. During the first elite testing clinic with USA Triathlon professional team members in 1990 exercise physiologists used HR, Lactate and RPE during testing of VO2max in swimming and running. And without exception athletes consistently rated the work intensity with precision simply by touching a point on the RPE scale.

There are many adaptations of the Borg scale but the exactness of the estimation of intensity is remarkably accurate. To be sure, there are few better ways to monitor effort than using perceptual sensations, feelings, muscular response and breathing rates to gauge and control exertion.

After all, there are many physiological, environmental and emotional variables at play. Experienced athletes by instinct identify the subtleties of increases and decreases in intensity relative to the length of competition, body temperature, respirations, environment, and nutritional needs and certainly, pace. If this weren't so HR monitors would be customarily used by the elite during competitions. They are not.

Now, one very useful aspect of HR monitoring and monitors is the regular collecting and assessment of morning heart rate and even this, should be in combination with other training, nutritional and resting factors. An innovative company like www.restwise.com is a good resource for both athletes and coaches who are interested in developing a more systematic method for managing training stimulus and recovery.

Successful endurance and triathlon outcomes are the result of the ability to sustain effort at or slightly above lactate threshold. This intensity is not so great the body's lactate buffering capacity is lessened. And using a HR monitor does not perceptually consider factors such as glucose depletion, environmental conditions and duration as HR remain level and even plateau as exercise durations extend while RPE rises and falls respectfully to changes in effort. You also need to "feel" then effort and adjust accordingly.

Though HR generally parallels RPE it can be altered for example by heat exposure, while RPE remains the same. So, RPE responds better to fatigue and intensity rather than the HR or power responses.

Studies demonstrate that HR response to exercise may fluctuate due to variables like sleep status, stress, dehydration, environment, illness, motivation, cardiac output improvement and cardiac drift. The latter occurs normally with corresponding increases in muscle temperatures. And can result in a HR drift of 20 beats a minute. Therefore, that little beating icon on your watch and power level do not always accurately identify intensity. HR monitoring and power training are good choices, but RPE works for any state of training and fitness whether an elite or novice.

Using Borg's scale, I adapted it using time and RPE conditional upon the duration of the interval, intensity or event duration (an early version can be downloaded at

evanscoaching.com. The Moving Bar of intensity scale is an additional tool that can be used in conjunction with HR and power.

The moving bars work simply enough using an athlete's intuitive internal feeling based upon the time of the interval or event. The shorter the interval the less time is used to measure effort. The athlete can clearly figure out intensity levels and how long these can be maintained and of course, pace.

For example, an Olympic distance triathlon for many triathletes is a test of pushing the highest levels of the anaerobic threshold (AT). A two minute bar is used for this distance. I tell athletes to ask themselves several times, Can I maintain this effort for the next two minutes? Once the question is asked and answered affirmatively the bar extends for another two minutes. In effect, the intensity level remains constant as the moves along with the athlete. At no time does the bar get closer to the athlete than two minutes. If there is ever a point where you cannot positively answer yes the intensity is too high.

In over-distance aerobic training the moving intensity bar ranges from fifteen to thirty minutes. A three-hour aerobic conditioning bike ride in the base preparatory phase has an RPE of extremely light to very light. The moving bar scale helps an athlete select intensities prior to workouts and remain consistent within the appropriate range of intensities.

- Marc Evans - www.evanscoaching.com (Coaching in Lake Tahoe, Your Venue or via Online Video)