For most long-distance athletes it is a big problem to determine the right level of training intensity. In many cases this will be judged by ‘gut-feeling’ or derived from race or test results. Nowadays, however, reliable measurements may be performed from which we may extract very useful information such as determination of the VO₂-max (= maximum oxygen-absorption capacity) or the heart-rate transition point also known as the anaerobic threshold. In this article we will discuss the latter method extensively.

Several possibilities exist to determine the anaerobic threshold, of which some examples are:

1. Well-trained persons may use as a rule of thumb "210 minus their age" for a coarse indication of the anaerobic threshold.
   
2. Another, very good approximation of the anaerobic threshold is the mean heart rate during a 15 km race.
   
3. PIAT-test (Probable Individual Anaerobic Threshold.
   
4. Laboratory test by performing a blood analysis. Regular measurement of lactate (from: lactic acid) in the blood by a medical doctor on the track is not something attainable for everyone.
   
5. The test of Conconi.
   

Since about a decade it is possible to determine the aerobic capacity by measuring the maximum volume (capacity) of oxygen absorption (VO₂max) and the lactate concentration in the blood. In cooperation with famous Italian endurance trainers (Lenzi etc.) the Italian biochemist Francesco Conconi succeeded in developing a simple, not blood-based test, which may give an indication of an athlete’s condition or state of training.

Energy conversion:

Our muscular cell is capable of converting chemical energy into mechanical energy, by which we are able to move. Energy-rich phosphates (ATP, CP), carbohydrates, and fats are available as fuel. If the load on the muscle is not high, the carbohydrates and fats may be fully burnt (oxidized) and converted into water and carbon dioxide, provided that oxygen is sufficiently present. This type of energy conversion is called aerobic.

However, if the body suffers from insufficient oxygen supply, or when intensive work has to be done immediately, then the muscle will use a second type of energy conversion that doesn’t depend on oxygen. This type of energy conversion is called anaerobic. Here, the energy may be extracted from either the energy-rich phosphates (a-lactic metabolism) or the conversion of glucose into lactic acid (lactic metabolism).

The transition from aerobic to anaerobic energy conversion is taking place at the so-called anaerobic threshold. This anaerobic threshold coincides with the transition point of the heart rate.

During a small physical load and a low level of intensity the body will obtain its energy almost exclusively from the aerobic metabolism, where the oxygen is taken in by the lungs and transported to the muscles through the heart-blood-vessel system.

After intensifying the load the muscle will consume more oxygen and the heart will have to work harder. Consequently, the heart rate will have to increase.

In the aerobic mode, in the range of heart rates of about 120 – 170 BPM (beats per minute), a linear relation exists between load (work intensity) and heart rate. At increased levels of intensity oxygen supply becomes insufficient and the required energy will have to be produced by the muscle without oxygen (anaerobic). The body uses the glycogen (a form of glucose) stored in the muscle, but it produces lactic acid when doing so. By now, the blood supply to the muscle and the accompanying heart rate will increase at a lower degree. Hence, a change will occur in the proportionality between work level and heart rate. In other words, the curve will show a kink, or a deviation from the straight line will become visible (see Figure 1).

Figure 1

Conconi was able to show that the kink will occur at the level of work intensity each time the production and the consumption of lactic acid are in balance. This implies that even for longer-lasting work on this level of intensity no increase of lactic acid concentration in the blood will occur. However, when the athlete passes this anaerobic threshold, after a while an accumulation of lactic acid will occur by tiredness of the muscles and the blood-circulation system, as a result of which he/she will have to reduce his efforts or even have to stop.

With some experience the aerobic capacity of a sportsman may be determined by determining the anaerobic threshold through a Conconi Test. On the one hand this test will enable us to get an indication of the endurance (staying power) of an athlete, and, on the other hand it offers the opportunity of heart-rate controlled training.

Despite some disadvantages (accommodation or settling time, problems with transmission of the heart rate, adjustment of running speed etc.) the test has proven itself according to Conconi. It is one of the success factors behind the Italian long-distance runners.

Conconi developed a method by which the anaerobic threshold was determined without using the lactate value, i.e. without blood sampling.

Conconi proceeded as follows:

During a test on a racetrack the relation between running speed and heart rate was determined.

A thorough warming-up of between 15 and 30 minutes was followed by a continuous run. During this endurance run, dependent on the protocol of choice, the speed was only slightly increased every 1000, 400 or 200 meters by no more than 0.5 km/hr.

After the data had been plotted in a graph, it was easy to determine the anaerobic threshold (see Figure 2).

Figure 2

In the article published by Conconi it was simply stated that the speed should be increased slightly every 200 meters and should be kept constant for the next 200 m.

"Simply stated but not very easy to achieve in practice".

As a trainer and coach of the (Track and Field Club) Atletiekvereniging Weert, The Netherlands, I devised a method that results in a more gradual increase in speed. By this method the speed of running is smoothly increasing by constant steps and this is controlled by an audio signal.

During the research it became apparent that the anaerobic threshold could be determined much more accurately when the steps in speed were smaller. This is a result of the fact that the heart may adapt its rate better (is lagging behind only slightly) if the speed is changing with smaller and more gradual steps.

The practical implementation of this finding is by making use of a cassette tape onto which the signals were recorded by a computer. These signals may then be transmitted to the attending athletes by a walkman or a P.A. installation.