Endurance Training

By Tudor O. Bompa, PhD

    For any nonstop sporting activity of 60 seconds or longer, endurance is an important, dominant contribution to the final performance. Factors affecting endurance, including willpower, speed reserve, and aerobic and anaerobic capacity, must be studied so training will thoroughly prepare athletes for the stresses of competition.

Classification of Endurance

    Endurance refers to the length of time that an individual can perform work of a given intensity. The main factor that limits and at the same time affects performance is fatigue. A person has endurance when he or she does not easily fatigue or can continue work in a state of fatigue. An athlete is capable of doing this if he or she is adapted to the specifics of the work performed. Endurance depends on many factors, such as speed, muscle force, technical abilities of performing movements efficiently, the ability to use physiological potentials economically, and psychological status when performing work.
    Considering the needs of training, there are two kinds of endurance: general and specific endurance. Ozolin (1971) considers general endurance to be the capacity of performing a type of activity that involves many muscle groups and systems (CNS, neuromuscular, and cardiorespiratory system) for a prolonged time. A good level of general endurance, regardless of the sport's specialization, facilitates success in various types of training activities. Athletes involved in sports in which endurance, and especially aerobic endurance, dominates do have a high level of general endurance. This suggests that there is a strong relationship between general and specific endurance. On the other hand, athletes taking part in sports of short duration or of high technical sophistication do not have a good level of general endurance. Every athlete needs general endurance. It assists in performing a high volume of work, overcoming fatigue in competitions of long duration, and recovering faster after training or competitions.
    Specific endurance, which often is referred to as endurance of playing, sprinting, and the like, depends on the particularities of each sport or the many repetitions of the motor acts of each sport. Although specific endurance is imprinted in the characteristics of certain sports, it may be affected by the excitement of competitions, the performance of difficult athletic tasks, or the type of training performed. Also, a demanding tactical game often affects an athlete's specific endurance; thus, the athlete may be subject to technical and tactical faults during the second part of the contest. Consequently, the stronger the specific endurance the athlete develops from a solid base of general endurance, the easier he or she can overcome training and competition stressors.
    The types of endurance presented are paramount to a successful performance in each sport. For cyclic sports, however, the following classification is often suggested (Pfeifer 1982).

• Endurance of long duration is required for sports that last for more than 8 minutes. Energy is supplied almost exclusively by the aerobic system, which greatly involves the cardiovascular and respiratory systems. During an endurance race in this category, the heart rate is high (over 180 beats per minute), the heart's minute volume (the volume of blood pumped by the heart in one minute) is between 30 and 40 liters, and the lungs ventilate 120 to 140 liters of air per minute (Pfeifer 1982). Obviously, for long duration races (i.e.., marathon) these values are lower. The O2 supply is a determining factor for a good performance. The vital capacity and the minute volume of the heart are, therefore, limiting factors for high athletic results. They also reflect the athlete's adaptation to the stress of such activities. Work of medium intensity favors the body's adaptation and capillary vascularization so vital for the supply of O2 to the muscle cells (Mader and Hollmann 1977).

• Endurance of medium duration is specific for sports and events in which work is performed during 2 to 6 minutes. The intensity is higher than in sports requiring endurance of long duration. The O2 supply cannot totally meet the body's needs; therefore. the athlete develops an O2 debt. The energy produced by the anaerobic system is proportional to the speed magnitude. Pfeifer (1982) claims that for a 3,000-meter run. the anaerobic system supplies approximately 20% of the total energy the athlete needs and, for 1500 meters, up to 50%. As in the previous case, the O2 absorption has a determinant role in performance.

• Endurance of short duration refers to sports in which the duration of the distance traveled is between 45 seconds and 2 minutes. For sports in this category. the anaerobic processes participate intensely in supplying the energy required to perform the athletic task. Strength and speed play an important role in producing high results. The O2 debt is high, and according to Pfeifer (1982), the anaerobic system provides 80% of the required energy for a 400-meter run and 60 to 70% for the 800-meter run. The basis for developing the anaerobic capacity is the aerobic capacity. Consequently, an athlete must develop a high aerobic capacity even for sports and events in this category. Muscle endurance. which I referred to in strength training, is facilitated by high strength development blended with adequate endurance. Sports such as rowing. swimming. and canoeing are the main beneficiaries of this combined ability.

• Endurance of speed represents athletes' resistance to fatigue under maximum intensity. Most of the work is done in apnea. which requires athletes to have both maximum speed and strength (also refer to speed training).

Factors Affecting Endurance

    Endurance, so important for good performance, is of different types. and its effective development depends on several training methods. In your quest to improve athletic performance. it is important to be aware of several factors. which may negatively affect the development of endurance.

Central Nervous System (CNS)
    During endurance training. the CNS adapts to the specifics of the training demand. As a result of training. the CNS increases its working capacity. which improves the nervous connections needed for well-coordinated functioning of the organs and systems. Fatigue. which often impairs training. occurs at the CNS level; therefore. decrease in the CNS working capacity is a major cause of fatigue. The struggle against fatigue is a battle of the nervous centers to maintain their working capacity.
    Increasing CNS endurance and its optimal status ought to be one of the main concerns in training. The coach can facilitate this by selecting adequate and optimal means of training. Uniform work with moderate intensity improves and strengthens the entire activity of the CNS. namely the neuromuscular coordination specific for endurance activities. Similarly, long-duration endurance activity performed under increasing levels of fatigue increases nervous cell resistance to stressful work (Ozolin 1971).

Athletic Willpower
    Willpower is a paramount ingredient in endurance training. The athlete requires it mostly when he or she has to perform work in a state of fatigue, or when the level of fatigue increases as a result of prolonged activity. This is even more obvious when intensity is an important component of training. The athlete cannot maintain the required level of intensity unless his or her desire and will order the nervous centers to continue the work or even increase it, particularly at the finish. Human beings do hold a great deal of endurance reserves, and we can maximize them only by appealing to the will to defeat the weaknesses, which may often result from fatigue. An important training objective, therefore, is to increase pain tolerance so athletes can psychologically tolerate the hurt, pain, and agony of training and competitions.

Aerobic Capacity
    The aerobic potential, or the body's capacity to produce energy in the presence of O2 determines the athlete's endurance capacity. Aerobic power is limited by the ability to transport O2 within the body. Developing the O2 transportation system should, therefore, be part of any program to improve endurance capacity. High aerobic capacity, which is vital to training, also facilitates faster recovery between and after training. A rapid recovery allows the athlete to reduce the rest interval and perform the work with higher intensity. As a result of shorter rest intervals, he or she can increase the number of repetitions, which increases the volume of training. A fast recovery rate, enhanced by high aerobic capacity, is also important in sports that require many repetitions of a skill (jumping events) or an increased number of bouts in team sports (hockey, football).
    The organs and especially the respiratory system that supplies the oxygen become well developed during endurance training. In fact, certain organs are developed according to the training method employed. Thus, interval training strengthens the heart, and high altitude or long-duration training increases the O2 using capabilities (Ozolin 1971). The aerobic capacity, however, relies on developing the respiratory system and correct breathing.
    Breathing plays an important role in endurance training. The athlete must perform it deeply and rhythmically, because active exhalation is critical for an adequate performance. Most athletes have to learn how to exhale to evacuate as much air as possible from the lungs, because the O2 has already been extracted. Without proper exhalation, the concentration of O2 in the freshly inhaled air will be diluted, which will adversely affect performance. A forceful exhalation is even more important during the critical phase of a race or game, when an adequate supply of O2 can enable athletes to overcome the difficulty. A high aerobic capacity positively transfers to the anaerobic capacity. If an athlete improves his or her aerobic capacity, the anaerobic capacity also improves, because he or she will be able to function longer before reaching an O2 debt and will recover more quickly after building an O2 debt (Howald 1977). This finding is significant for most sports in which the anaerobic capacity is an important component. Most team sport athletes would maximize their technical and tactical knowledge by improving aerobic capacity. Improving aerobic endurance must be a permanent goal for most athletes.
    A strong aerobic capacity also stabilizes speed. The competitive phase of many sports emphasizes anaerobic capacity, but often the consistency of anaerobic performance is affected by exaggerated, stressful, intense work. When anaerobic capacity is an important component of training, you must also introduce aerobic activities to prolong a successful performance. In such cases, training lessons stressing aerobic long-duration endurance alternate activities of various intensities. Under these new conditions, the body can regenerate and thus increase the durability of anaerobic power. The same concept is valid for the unloading (tapering) phase. When athletes reduce their training demands before important competitions, introduce training lessons of aerobic activity to replace stressful intensive activities. As a result, the body will regenerate, because the load is lighter, and the degree of training is not affected. Howald (1977) implies that there is a trend showing that athletes using long-duration sub-maximum training do have higher anaerobic thresholds than those using more high-intensity endurance and interval training. Consequently, based on these realities, coaches should revise their training concept and introduce a much higher percentage of aerobic activities into their training programs.

Anaerobic Capacity
    In the absence of O2, energy is produced by the anaerobic system for sports that demand maximum exertion and those requiring sub maximum exertion during the initial stages. Energy contributed by the anaerobic system directly relates to the performance intensity. For example, if an athlete runs a 400- meter race with a velocity of 7.41 meters per second, the ergogenesis (the production of energy) is 14% aerobic and 86% anaerobic. Running the same distance with a velocity of 8.89 meters per second, the ratio is 7.7% aerobic and 92.3% anaerobic (Razumovski 1971). It appears, therefore, that the use of the two energy systems depends on the distance of the race and the classification or performance level of an athlete. It is obvious from this example that the two systems can provide energy in various proportions. The proportion of the aerobic component increases as the distance increases and the intensity decreases.

    Ozolin (1971) claims that the body's anaerobic capacity is affected by the CNS processes, which facilitate continuing intensive work or work under exhausting conditions. Research also suggests that the anaerobic capacity is affected by hyperventilation, or inhaling additional O2 through increasing the respiration rate before the start.
    Specific training in the respective sport is the best method of improving the anaerobic capacity. As explained, however, anaerobic training often has to al- ternate with aerobic training. Aerobic training should predominate for sports that last longer than 60 seconds. Anaerobic training, such as the over emphasized interval training used in North America, will not necessarily make athletes faster who compete in sports lasting longer than 2 minutes. It is helpful only for the first part of the race.

Speed Reserve
    One factor that affects endurance, especially specific endurance, is the speed reserve. Its importance in cyclic sports may often be determinant, although many coaches are still unaware of this or disregard it. Speed reserve is the difference between the fastest time achieved on a distance much shorter than the racing distance (i.e., 100 meters) and the same short distance during a longer race (i.e., 800 meters). To have validity, perform the test during the same time. An athlete who can cover a short distance fast will be able to travel longer distances at a lower speed more easily. Under such circumstances, an athlete with a higher speed reserve would spend less energy to maintain a given speed compared with others with a lower reserve.
    You can perform a speed reserve test as follows. The coach should first determine the distance to test. A standard speed distance for mid-distance running is 100-meter dash; for swimming either 25 or 50 meters or one length of the pool; for rowing 500 meters, and canoeing 250 meters. Then test the athletes to determine the maximum speed with which they can cover the standard distance. The next step would be to test the athletes' speed over the standard distance, for example 100 meters, while they compete over the distances in which they specialize.
    Let 11 seconds be the maximum speed over 100 meters and 12.4 seconds the time achieved over 100 meters while running 400 meters. The difference of 1.4 seconds is the speed reserve index; the larger the difference the greater the speed reserve. A good speed reserve and systematic specific endurance training will lead to high performance in the chosen event. Similarly, provided that athletes have a good speed, the smaller the index the better the specific endurance. Although this aspect of training is inadequately researched, it is obvious that there is a strong interdependence between speed reserve and athletes' ability to reach a high performance. An athlete running 100 meters in 10.6 seconds, even without much specific training, would cover 400 meters in 50 seconds. This means a speed reserve of probably 1.8 seconds and a mean speed of 12.5 seconds. An athlete with a speed of 12 seconds per 100 meters would, however, have a hard time or may even be unable to perform a similar time over 400 meters. Speed in general and a speed reserve in particular may, therefore, be a limiting factor in athletic progress.

Methodology of Developing Endurance

    To improve endurance, athletes must learn to overcome fatigue, and they do this by adapting to the training demand. Any degree of adaptation is reflected in improved endurance.
Athletes must develop the two types of endurance, aerobic or anaerobic, primarily according to the specifics of the sport or event. Developing these two types of endurance depends on the type of intensity and the methods used in training. Although other classifications of intensities are used in training, the absolute intensity in endurance training is linked with the energy supply systems. Thus, Zatzyorski (1980) considers the following three intensities: sub-critical, critical, and supra-critical.
    The sub-critical intensity has reduced speed, a low energy expenditure, and an O2 demand below the athlete's aerobic power. The O2 supply meets the physiological demand; therefore, the athlete performs the work under the steady state condition.
    The athlete achieves the critical intensity when the speed increases and the O2 demand reaches the supply capacity. The athlete performs the critical intensity in the anaerobic threshold zone; thus, the speed is directly proportional to his or her respiratory potential.
    Supracritical speed refers to activities that are faster than the critical speed. The athlete performs the work under O2 demand, which usually increases faster than the performance speed.

Training Parameters for Aerobic Endurance

    The physiological threshold of various organs and systems involved in aerobic activity increases and develops more efficiently when training consists of low- intensity, long-duration work. If the activity is continuous, it is a difficult task for an athlete's body to maintain the O2 consumption so specific for aerobic endurance. Usually, the duration of work under maximum O2 consumption cannot exceed 10 to 12 minutes, except highly trained athletes (Zatzyorski 1980). Elite-class athletes from sports such as running, cross-country skiing, rowing, swimming, and so on may maintain a velocity close to the critical level for between 1 and 2 hours (heart rate 150-166 beats per minute).
    As a general outline, the following training parameters are significant for developing aerobic endurance.

• The intensity of training must be lower than 70% of the maximum velocity (Herberger 1977). As a criterion to follow, you can measure the intensity by the time of performance per a given distance, the velocity in meters per second, or the heart rate (140-164 beats per meter). Training stimuli that do not elevate the heart rate above 130 beats per minute do not significantly increase the aerobic capacity (Zatzyorski 1980).

• The duration of an isolated stimulus (i.e., one repetition) has to be of several varying magnitudes. Sometimes it must be 60 to 90 seconds to improve anaerobic endurance, which is an important component during the beginning of a race. Often, however, athletes use and need long repetitions of 3 to 10 minutes to perfect aerobic endurance. The general composition of a training program depends, however, on the phase of training, the characteristics of the sport, and the needs of the athlete.

• Calculate resting intervals so the following stimulus occurs during the period of favorable changes previous work provoked. According to Reindel, Roskamm, and Gerschler (1962), it has to be between 45 and 90 seconds. For aerobic endurance, however, the rest interval definitely should not exceed 3 or 4 minutes, because during a longer rest the capillaries (the blood vessels that connect the arteries with veins) shrink, and for the first minutes of work, blood flow is restricted (Hollmann 1959). The same author suggests that you can also consider the heart rate method for calculating the rest interval. Usually when the heart rate drops to 120 beats per minute, work can commence.

• Activity during the rest interval is normally a low intensity to stimulate biological recuperation. In athletics, walking or jogging are familiar activities for well-trained athletes.

• Determine the number of repetitions by the athlete's physiological capacity to stabilize O2 consumption at a high level. If this stabilization does not occur at a sufficiently high level, the aerobic system will be unable to meet the energy demands. Consequently, the anaerobic system takes up the slack, which puts a severe strain on the body and results in fatigue. As suggested by Zatzyorski (1980), the heart rate may be a good indication of the level of fatigue. The heart rate increases as fatigue develops and the athlete performs equally strenuous repetitions. Once more than 180 beats per minute or so, which reflects a high level of fatigue, the heart has less contracting power, resulting in less O2 to the working muscles. At this point, or shortly before, the athlete should cease training.

Training Parameters for Anaerobic Endurance

Anaerobic endurance represents an important physiological asset for many sports, including team sports. Most of the means for developing anaerobic endurance are cyclic and performed with high intensity. The coach may use the following brief presentation as a general guideline in training.

• The intensity may range from submaximum up to maximum limits. Although you use a variation of intensities in training, for improving anaerobic endurance, intensities around 90 to 95% of maximum ought to prevail.

• The duration of work may be between 5 and 120 seconds, depending on the type of intensity the athlete uses.

• The rest interval following an activity of high intensity must be long enough to replenish the O2 debt. This may be within 2 to 10 minutes, because the interval of recuperation is a function of the intensity and duration of work. For more efficient recuperation and replenishment of fuel to provide required energy, I advise you to divide the total number of repetitions into a few series of four to six repetitions each. Plan the longest rest interval of 6 to 10 minutes between sets so the accumulated lactic acid will have sufficient time to oxidize. The athlete can then start the new set almost recovered.

• Activity during rest has to be light and relaxing. Total rest (i.e., lying down) is inadvisable, because the excitability of the nervous system may decrease to unacceptable levels (Zatzyorski 1980).

• The number of repetitions must be low to medium, because work for developing anaerobic capacity is intense and cannot have too many repetitions without accumulating lactic acid (LA). If work continues, the glycolytic resources become exhausted, which means that the aerobic system must assume responsibility for providing the required energy. Under this circumstance, the velocity decreases and, consequently, the work will not benefit the anaerobic capacity. It seems that the best method is to divide the planned number of repetitions into several sets, say four sets of four repetitions. The rest interval between repetitions may remain as planned (i.e., 120 seconds), but between sets it has to be long enough (i.e., up to 10 minutes) to replenish the O2 debt and consequently oxidate LA.

Endurance-Training Programs Based on the Lactic Acid Method

    Contemporary training is complex. To direct adequate programs, the coach often needs to discover precisely the internal dosage and how the body responds to training stimuli. The LA (lactic acid) method refers to detecting the quantity of LA present in the blood as a result of training. Although the method is not complicated, it does require the scientific assistance of a physiologist. To put it simply, a blood sample is taken from the ear lobe and analyzed to determine the LA concentration. According to the LA concentration, divide the effort in training into four zones (Marasescu 1980), illustrated in12.1. table

TABLE 12.1    Four Zones of Effort Based on the LA Method

    The first zone refers to activities such as jogging for warm-up, compensation activity between repetitions, and light activities at the end of a training lesson. The second zone is the more difficult work of aerobic endurance exercises. The third zone is a typical program combining aerobic and anaerobic programs. The last zone refers strictly to intense, anaerobic activities.
    Data interpretation is simple. By comparing the LA concentration to the data in table 12.1, you can make alterations in the program, depending on the type of training required. Often a coach's intention is an aerobic workout, but based on the LA method, the reality may be that the athlete worked harder, performing an activity of the third or fourth zone. As a result, the coach must change the program. The LA method may also illustrate other features of the athlete's training. For instance, the lower the LA concentration is following hard work, the better the athlete's training capacity. On the other hand, the higher the LA concentration following an anaerobic training, the better the athlete mobilized the anaerobic mechanism.
    The correct combination of work from the four zones (table 12.1) in training may lead to an objective method of directing a program. Table 12.2 illustrates two combinations that you could use as guidelines for a correct program in a given training phase.
    The combination of activities for endurance training, and especially the percentage per combination, represents additional proof of the importance of the aerobic component in any endurance-training program.

TABLE 12.2 Combinations of Activities According to the Objective of Endurance Training

Methods to Develop Endurance

    Throughout all development phases, especially the phase of perfecting endurance, adjustment to the physiological limitation of endurance training is crucial. Physiological limitation (tissue adaptation to work under the conditions of insufficient O2 or hypoxia, an excess of carbon dioxide) is always accentuated when athletes reach a high state of fatigue. In addition to classical methods of furthering the body's adaptation to a higher endurance demand, which are briefly described here, you may consider other techniques. Breathing at a lower rate than the body and rhythm of performance demand may artificially create a state of hypoxia (i.e., to breathe once at every 3-4 swimming strokes). Training at a medium or high altitude where the partial pressure of O2 is lower leads to the same result, which is training under the conditions of hypoxia. Many East European athletes do this twice a year for 2 to 4 weeks. Another positive result of using these two techniques is the increase of hemoglobin content in the blood. Hemoglobin is an iron-containing protein pigment present in the red blood cells and functions primarily in transporting O2 from the lungs to the muscle tissue.

Long-Distance Training Methods

    One characteristic of all training methods in this category is that work is not interrupted by rest intervals. The most commonly used methods are as follows: uniform or steady state, the alternative, and the fartlek method.
 

Uniform Method
    The uniform method is characterized by a high volume of work without any interruptions. Although it is used throughout all annual training phases, this method dominates during the preparatory phase. I highly recommend it for sports requiring aerobic endurance, but mostly for cyclic sports with a duration of 60 seconds or more. The duration of one training lesson may be between 1 and 2.5 hours. You can properly calculate the intensity by using the heart rate method, and the rate should be between 150 and 170 beats per minute.
    The main training effect is improving and perfecting aerobic capacity. Similarly, the steadiness of performance leads to consolidating technique (i.e., speed skating, swimming, canoeing, rowing), while improving the working efficiencies of the body's functions.
    A variant of this method is to progressively increase the speed from moderate to medium intensity throughout a training lesson. For instance, the athlete may perform the first one-third of the training distance at a moderate speed, increasing it to intermediate, and finally to a medium intensity for the last one-third. This is an effective method of developing aerobic endurance be- cause the progressive elevation challenges the athlete both physically and psychologically.
 

Alternative Method
    The alternative method is one of the most effective methods of developing endurance. Throughout the lesson, the athlete changes the performance intensity over a predetermined distance. The intensity of work varies frequently from moderate to submaximum without any interruptions. You can determine the variation of intensities by external factors (terrain profile for running, cross-country skiing, and cycling); internal factors (athlete's will); and planned factors (coach's decision regarding the portion of distance to alter the intensity). Alternate the peak velocity of 1 to 10 minutes with moderate intensity, which will allow the body to recuperate slightly before another increase. For high velocity stimuli, the heart rate may reach values around 180 beats per minute, and the restoration phase may have the rate around 140 beats per minute (Pfeifer 1982), but not much lower than that. The rhythmical, wavelike approach in altering the intensity facilitates a high volume of work, improving the cardiorespiratory and CNS capacity significantly. In addition, this method promotes a flexible adaptation of the body's processes, resulting in a strong development of general endurance. You may apply this method with those involved in cyclic sports during the precompetitive and competitive phases, as well as others (team sports, wrestling, boxing) during the preparatory and precompetitive phases.
    An excellent variant of this method is to organize the entire training program into sets. Instead of performing uninterrupted work of say 90 minutes, divide it into three sets, with an active rest (i.e., walk) between each set.

Fartlek Method
    The fartlek or speed-play method was developed by the Scandinavian and German runners from 1920 to 1930. While performing, the athlete inputs his or her own contribution by alternating uniform training at will with short portions of higher intensity performance. Such sprints are not planned and rely mostly on the athlete's subjective feeling and judgment. The use of the fartlek method is specific mostly, but not entirely, to the preparatory phase, to interject variety into the monotony of uniform training.

Interval Training

    Interval training is a highly taxing type of training that we could compare with the extremely strenuous work performed by Sisyphus. According to Greek mythology, Sisyphus was the king of Corinth and well known for his craftiness, when Hades, the god of death, came to get him. Sisyphus tricked Hades and put him in chains. Hades eventually escaped and punished Sisyphus for his trickery. The sentence was that Sisyphus would eternally push a huge stone to the top of a hill. Every time Sisyphus reached the summit the stone would roll back down, forcing him to start his work again and again and again.
    Those who want to experience interval training had better remember the work of Sisyphus! The term interval training does not necessarily refer to a well-known method, but to all methods performed with a rest interval (figure 12.1).

Repetition Method
    The repetition method of distances longer or shorter than the racing distance, develops specific or racing endurance. Longer repetitions place a strong demand on the aerobic component of racing endurance, because the performance speed is close to the racing speed. On the other hand, shorter repetitions solicit the anaerobic component, because the performer often develops an O2 debt. Obviously, in the latter case, the intensity is slightly higher than that of a race. An important asset of the repetition method is developing willpower through the demand to perform many repetitions. The total volume of work may be four to eight times that of the racing distance, with a rest interval between 5 and 10 minutes, depending on the repetition distance and intensity.

Model Training
    Consider model training a variation of repetition training, because an athlete experiences repeating several training distances. The originality of this method lies in that it resembles the specifics of the race, hence the name model training. The first part of training consists of several repetitions that are much shorter than the racing distance, performed with an intensity close to (slightly higher or lower) racing velocity. Under such conditions, the anaerobic metabolic system provides the energy, as in a race. The midpart of training uses distances and intensities that improve and perfect the aerobic endurance. The last part of training again employs short-distance repetitions to exactly model the race, which resemble and develop the final kick capacity. The athlete performs these repetitions under a certain level of fatigue as in the race and heavily tax the anaerobic endurance, which considering its specifics we may call speed of endurance.
    Calculate factors such as total volume of work, velocity, rest intervals, and the number of repetitions according to the individual's potential and the characteristics of the sport. You can use the heart rate method for calculating the rest interval. Considering its specificity, employ this method during the precompetitive and competitive phases.
    Interval training, a method that was in fashion in Europe in the 1960s and overrated in North America even in the 1980s and 1990s, is rightly reconsidered for its merits in developing endurance. Most exaggeration about interval training came from the fact that repetitions of short duration were expected to improve everything, including aerobic endurance. Obviously, this was never the case. There is no one method that can do everything for everybody. Only a wise combination of all methods knitted together according to the needs of the athlete and the specifics of the sport may be successful. Interval training as it is best known, with duration of stimuli between 30 and 90 seconds, inadequately develops the aerobic energy production system and the capacity to maintain what development there is throughout the competitive phase.

    Interval training refers to the method of repeating stimuli of various intensities with a previously planned rest interval, during which the athlete does not fully regenerate. The coach calculates the duration of the rest interval by the heart rate method. The athlete could repeat the portions of distance either by time (i.e., 12 x 3 minutes) or precise distance (12 x 800 meters). For a more efficient training effect, combine all three interval training methods.

• Short-distance interval training, between 15 seconds and 2 minutes, which mostly develops anaerobic endurance

• Medium-distance interval training, 2 to 8 minutes, which may develop both energy production systems

• Long-distance interval training, 8 to 15 minutes, with a main training effect of aerobic endurance improvement

    The main elements of progression are intensity and duration of stimuli, the number of repetitions, rest interval, and activity during rest.

Specific Racing Endurance

    You can develop specific endurance by what Pfeifer (1982) calls control or racing method. As the term suggests, using such a method exclusively develops the endurance specific for each event or sport. Calculate the training dosage so it corresponds specifically to physical, psychological, and tactical characteristics of the selected sport (figure 12.2).
    Developing endurance is a complex task, because in most sports there are combinations of aerobic and anaerobic components. Consequently, to achieve a complex body adaptation, you must use several of these methods and variants. The physiological effect of a method does not, however, have to be the only criteria for selecting a training method, as there is also the psychological benefit of a method. Apparently from a psychological point of view, training methods developing aerobic endurance (uniform and alternative) are superior to interval training (Pfeifer 1982).

FROM: PERIODIZATION, By Tudor O. Bompa, PhD