The use of a heart rate monitor is often prescribed within the context of training protocols. The monitor is used in such a way as to ensure that the athlete remains within certain heart rate parameters, according to the particular training stimulus being pursued in that moment. These parameters are generally expressed as a percentage of maximum heart rate (MHR), or, for highly trained athletes looking to improve further, as a percentage of the Lactate Threshold (LT), which is a more accurate reference point for the training "sweet spots".
Therefore utilising the MHR as the guideline easy recovery exercise would be defined as being between 60-70% of MHR, the aerobic level between 70-80% of MHR, anaerobic exercise (and consequentially the LT) between 80-90% of MHR, and intense short burst or VO2Max activity between 90-100% of MHR.
Alternatively utilising the Lactate Threshold as the guideline we would have easy recovery work at 70-80% of LT, aerobic exercise at 80-95% of LT, the anaerobic level at 95-105% of LT, and intense activity at 105-115% of LT.
There are, however, a number of problems involved in this process.
MHR is a particularly difficult number to accurately define even in laboratory conditions. Although it is a fixed rate and cannot be changed by training, though it will be diminished by age, it is subject to external factors such as heat, levels of hydration and stress. Without a laboratory test it is extremely difficult to determine. There exist many formulas for the calculation of the theoretical maximum heart rate. For example the simple 220 – age which is highly inaccurate.
Alternatively the Karvonen Formula for establishing minimum (corresponding to a minimum aerobic intensity level) and maximum (corresponding to an approximate LT) heart rate levels for training protocols. It is clear that the heart ranges deduced from such formulas, for subsequent use with the heart monitor, are themselves subject to approximation, and therefore the only accurate method of knowing the MHR is undergoing an expensive laboratory test in which both the MHR and LT can be determined. Only in such a condition can a truly accurate use of the heart monitor be made.
Although I personally prefer the use of a heart rate monitor in order to elicit precise training responses, I have to acknowledge that many athletes involved in Trail and Mountain Running are rather diffident to the use of technology based upon methods such as laboratory tests, heart monitors and strict protocols. Does there exist a valid alternative for training at the correct levels without the use of technology?
A number of researchers have proposed the use of "Rate of Perceived Exertion" scales in which the level of training intensity is measured through the personal sensations of the individual athlete to intensity.
One of the first RPE scales was the 20 point exertion scale as proposed by Borg in 1982 in his paper – “Perceived Exertion and Pulse Rate during Graded Exercise in Various Age Groups.” Borg G, Linderholm H, University of Umea, Sweden. This proposal was made within the context of medical patients during periods of recovery and rehabilitation and is, as may seem clear to any trainer or athlete too complicated and articulated for use in training protocols.
This was subsequently reformulated to a system of 10 points which is more functional simply due to the fact that we are trained from a very young age to utilise a mathematical and valutational scaling system of 10.
As may be observed the levels of difference are reasonably well defined and identifiable by the majority of athletes, though some degree of approximation remains.
Numerous studies have been made in order to evaluate the validity of the system of RPE. In their paper “A new approach to monitoring exercise training” , Foster C et al, published in the Journal of Strength and Conditioning, 2001, the authors concluded that “………the session RPE method is a valid method of quantitating exercise training during a wide variety of types of exercise. As such, this technique may hold promise as a mode and intensity-independent method of quantitating exercise training and may provide a tool to allow the quantitative evaluation of training periodization plans.”
Similarly Roger Eston writing in the International Journal of Sports Physiology and Performance, 2012 asserted that “……….RPE is valid for monitoring, prescribing, and regulating exercise intensity and assessing training load. It has been used to explain changes in pace and pacing strategy, as the rate of RPE progression during competitive situations is related to duration and certainty of the end point.” (Use of Ratings of Perceived Exertion in Sports).
It would therefore appear that the use of the RPE method is a valid alternative but how can an athlete identify the levels of training intensity as proposed in the majority of protocols (usually in terms of HR expressed as a percentage of MHR or LT) with these Rates of Perceived Exertion (RPE). For practical purposes we can identify the following levels.
RPE. % MHR. % LT. Intensity
1-2. <60% <70% Recovery
3-4. 60-70%. 70-80%. Aerobic
5-6. 70-80%. 80-95%. Aerobic Threshold
7-8. 80-90%. 95-105%. Anaerobic Threshold (LT)
9-10. 90-100%. 105-115%. Intense activity / Maximum
From the above we can therefore deduce that the following training activities correspond to the various RPE. Easy recovery work should be undertaken at level 1-2, normal aerobic training (long run) at level 3-4, steady state or race pace training at level 5-6, anaerobic training (intervals, hill repeats, fast tempo work) at level 7-8, very fast, sprint or fast twitch muscle activity at levels 9-10.
Other proposals have been made, for example that of a 5 point system by Joe Friel, specifically for his work in triathlon, however, as can be observed, the compression of the various levels renders the identification of the specific level with the perceived intensity a more complicated task and it has been necessary to provide sub classifications within the two top levels.
Joe Friel, 2010 “Joe Friel’s Quick Guide to Training with Heart Rate, Power and Pace”
This system can be considered more suitable for use with elite athletes who are more attuned to their body's reaction to training, and are therefore able to grade perceptions of intensity with more precision. Due to the more precise nature of this 5 point scale it would also appear difficult to use within the context of trail or mountain running where the nature of the terrain can have a significant effect on the perception of exertion
As can be seen from the above the use of a scale of RPE can quite successfully substitute the use of a heart rate monitor within a program of training. Neither RPE nor heart rate monitor, unless the MHR and LT have been established through a laboratory test, are 100% precise methods of establishing the correct level of intensity for training sessions and often there is very little difference in the accuracy of the results. It remains to be said that the use of the RPE requires the athlete to be attuned to the reactions of his organism to activity at all levels from easy through hard, and that this may require a period of training, experimentation and observation in order to produce the best results. Above all the use of RPE requires a degree of personal honesty and integrity in order not to be influenced by the activity of regular or occasional training partners.