Measurement of intensity is a particularly difficult issue in training. Often, even experts in the field cannot aggree.
Along with measuring duration and frequency, accurate measurement of intensity is paramount to the construction of an effective training plan. It is well known that cyclist who do not accurately gauge intensity tend to do too much training of medium intensity. Easy rides are often ignored, and as a result, the athlete is unable to adequately partake in hard efforts due to fatigue. The most effective training program will use high intensity efforts judiciously, while allowing adequate recovery.
Measuring intensity is far more difficult than measureing duration or frequency. The major issues in measurement of intensity is reproducibility and generalizability. All intensity categorizations must be reproducible in order to be useful. That is, the athlete should be able to replicate intensity on a day to day basis. If an athlete performs 'Ten minutes in Zone IV' today, it should feel relatively as hard, accounting of course for improvement and fatique, as the same workout done at a later date. Attainment of reproducibility is difficult, but can usually be obtained over time, by the use of objective measures and by increasing athlete experience. Conversely, attainment of generalizability is far more difficult. Generalizability means that a given workout should seem relatively as hard amoung different athletes. For instance, all athletes, regardless of fitness level, should feel that One hour in Zone V is a hard workout. For the coach or fitness instructor, this is vital for construction of a sound training plan. Nonetheless, finding an objective measure which is both reproducible and generalizable is difficult.
To measure intensity, four common methods are available.
Measurement of intensity by Relative Perceived Index (RPI) has been used for many years, and in the hands of experienced athletes can be very effective. In this method, athletes rate their exertion on a scale, usually from one to ten, with one being very minimal exercise, and ten being full out exertion. Advantages include the ability to rate exertion without any electronic or mechanical devices; the method is accessible to anyone. Disadvantages include intra- and inter-athlete variability, and the tendency for fatigue to influence the objective rating.
The second most common method involves use of heart rate, measured either by direct palpation of the pulse, or by an electronic heart rate monitor. Target exertion zones may then be obtained by one of four methods:
Percentage of Maximum Heart Rate: Target zones here are based on the athletes measured or calculated Maximum Heart Rate. This method, although technically the easiest, is inaccurate and not recommended. In general, maximum heart rate has little relationship to fitness or to the athletes actual intensity levels.
Percentage of Lactate Threshold: Target zones are calculated as a percentage of the athletes LTHR, which is measured commonly by one of three methods:
Laboratory Measurement of Serum Lactate: Usually a graded exercise test is performed. LTHR is determined at the point when the athlete is producing Lactate at a rate that
Calculation via the Conconi Test: This test, developed by legendary Italian physiologist Conconi, measures output vs heart rate in a graded exercise test. The results are graphed, an inflection on the graph is assumed to be the LTHR.
Calculation on 60 Minute Time Trial: The assumption is made that the athletes average heart rate for the final 55minutes of a one hour time trial is a good approximation of LTHR.
Percentage of CHR60: Target zones are calculated as a percentage of the 60 minute critical heart rate. This is similar to 2c above. However, in this case, no assumption is made that this value actually reflects LTHR.
Direct Measurement of Critical Powers: A time trial is performed for a specific length of exertion for each target zone. This method may be more accurate than method 3 above, however, it does involve significantly more commitment from the athlete.
Advantages include low price of equipment and a more objective measurement when compared to RPI. However, this method does not directly measure output, and thus can lead an athlete to believe output is high, when in fact heart rate is artificially elevated. In addition, it may be possible that measuring intensity by heart rate monitor may encourage a less economical style. Why? Since athletes are judging exertion by heart rate, it seems likely that the athlete will subconsciously develop a style which encourages the highest heart rate with the least exertion.
Thirdly, intensity may be measured with a power output device, producing a numerical measurement of intensity in the form of Wattage. Recently, several methods of direct power output have been marketed including the SRM PowerMeter, the PowerTap, the Computrainer, the Cateye CycloSimulator, and others. In this case, intensity is based only on output. Intuitively, this method may be seen as the most objective. Usually, the rider will measure average output for several lengths of ride; a Critical Power is calculated: the highest possible average power for a given length of time. Thus, each intensity zone is related to a specific numerical power output. The obvious advantage of this method is objectivity. There is no way a rider can falsely elevate his or her output. In addition, once critical power is determined for each athlete, it seems likely that this method will be the most generalizable. Disadvantages include cost, inconvenience, the inavailability of measurement for most cross training methods, and the tendency for athletes to neglect their own feelings of fatigue in order to complete a workout. In addition, consistant monitoring would require the athlete to have powerer measurement for every workout. Lastly, since at present these devices are heavy and cumbersome, their use during race situations in limited.
A fourth method of intensity is available, but limited to laboratory situations. Direct measurement of blood lactate levels during exercise may be the best method to attain the true value of the Lactate Threshold. This test is usually used to obtain the Lactate Threshold Heart Rate. From there, Intensity Zones are calculated as percentage of LTHR, and the athlete uses a heart rate monitor during exercise to measure intensity. At present, this method is limited to laboratory use. In addition, for many riders laboratory LTHR has little relationship to RPI. This may make determination of target intensity zones more difficult.
Because most riders do not have constant access to power monitors, most VRS programs are based on Heart Rate measurement.
Furthermore, since most athletes do not have a serum lactate threshold test performed, most VRS programs will divide Intensity Target Zones by Critical Heart Rate (CHR). Initially each target zone will be calculated from the riders CHR60. These exertion levels can later be fine-tuned by the athlete.
|
Zone |
Name |
Metabolism |
CP CHR |
Heart Rate |
Exertion |
Flat |
Hill |
|---|---|---|---|---|---|---|---|
|
Minute |
%LTHR |
x/10 |
|||||
|
R |
Resistance |
N/A |
N/A |
N/A |
N/A |
||
|
O |
Recovery |
Aerobic, Lipolysis |
>180 |
<65% |
<4 |
Anquetil |
XXXX |
|
I |
Extensive Aerobic |
Aerobic, Lipolysis |
>180 |
65-81% |
4 |
Riis, |
XXXX |
|
II |
Intensive Aerobic |
Aerobic, Lipolysis |
>180 |
82-88% |
5 |
Riis, Hincapie, Lapize |
Brown |
|
III |
Tempo |
Aerobic, Lipolysis |
150 |
89-93% |
6 |
Ulrich |
Casagrande |
|
IV |
Sub-Threshold |
Aerobic with increasing Lactate |
60 |
94-100% |
7 |
Indurain |
Mercx, Pantani |
|
Va |
Supra-Threshold |
Aerobic and Anaerobic |
30
|
100-102% |
8 |
Lemond, Martinez |
Armstrong, Pantani, Hampsten |
|
Vb |
VO2 Max |
Anaerobic and Aerobic |
12 |
103-105% |
9 |
Miller |
Vireque |
|
Vc1 |
Lactate Tolerance |
Anaerobic (lactacid) |
1 |
>106% |
10 |
Ekimov |
Ekimov |
|
Vc2 |
Power |
Anaerobic (alactacid) |
0.2 |
>106% |
10 |
Steels |
Zabel |
|
M |
Mobility |
Anaerobic (alactacid) |
N/A |
N/A |
N/A |
Cipollini, Reyes |
XXXX |
CHR=Critical HR for the duration specified. For example, CHR60 is the average HR for a 60 min TT
CP=Critical power for the duration specified. For example, CP60 is the average power for a 60 min TT