5 Energy Systems Used In Exercise We Must Know

In all athletic programmes the intensity of training must be altered throughout a micro-cycle in order to enhance both the athletes’ physiological adaptation to training, as well as the regeneration following a demanding training session. However, such alternation of intensities depends on the ergogenesis of the event and the characteristics of the training phase.
As far as the physiological profile of an endurance related event is concerned, in the first 15-20 seconds the energy demands are supplied by the phosphate system (ATP/CP), followed by the lactic acid LA system up to 1: 30-2 minutes. If the event continues for a longer period of time, then energy demands are supplied by glycogen which in the presence of O2 is completely burned without producing lactic acid.
Therefore, since most sports use fuel produced by all the energy systems, training has to be more complex, exposing the athletes, especially during the last pan of the preparatory and the competitive phase, to all energy systems.
In order to assist coaches to conduct more scientific and better planned training, which has to consider the physiological profile and the energy requirements of a sport, five intensity values are proposed (figure 108). These intensities are listed from 1 to 5, in order of the magnitude of training demand: number 1 being the most, and 5 being the least taxing. For instance, the Lactic Acid Tolerance Training (LATT) is regarded as physiologically the most demanding, therefore it is considered as intensity number one (1). On the opposite end of the scale are the phosphase system training (number 4) and aerobic threshold training, (number 5) since the body can tolerate them much easier.

The heading of figure 108 explains the physiological characteristics of each value, which should be regarded as a training method. For instance,. if the coach intends to use Lactic Acid Tolerance Training, he/she may employ one of the two durations suggested, with a set number of repetitions and a rest interval (RI) sufficient to remove the lactic acid from the system. The coach will also consider the corresponding ratio of work to rest interval, lactic acid concentration in milimoles (mmol) and the heart rate (HR). In order to reach such physiological characteristics the percentages of maximum intensity for the early and late preparatory phases are also suggested. The latter intensity also refers to the competitive phase. For a better understanding of the five intensities, each method is briefly explained below.

Training the Energy Systems: The Five Intensity Values
Figure 108.   Suggested guidelines for training the five intensities of the energy system ( “represents seconds, minutes,and hours).

Lactic Acid Tolerance Training (LATT)

Athletes who can tolerate the pain of acidosis can perform better longer. Therefore the scope of LATT is to adapt to the acidic effect of LA, to buffer the LA effects, increase lactate removal from the working muscle, and to increase tolerance physiologically and psychologically to the hurt, pain and agony of training and competition. By adapting and learning to tolerate LA increases, the athlete can work more intensely and produce more LA which should not be inhibiting. Thus, towards the end of an event, more energy can be produced anaerobically. Maximum limits of LA tolerance can be reached in 40-50 seconds.

Recovery periods should be long enough to remove LA from the working muscle (15-30 minutes), otherwise the removal of LA will be prevented, acidosis being so severe that reduction in energy metabolism will cause a reduction in speed below the level necessary to increase the LA production. Thus the intended training effect would not be realized. Work periods of less than one minute require several repetitions (i.e. 4-8). Longer work periods (i.e. 2-3 minutes) are desirable, but only if the speed is sustained at a level high enough to cause excessive LA accumulation (12-16 mmol) thus producing high levels of aerobic power under conditions of extreme acidosis Psychologically, the purpose of LATT should be to push the athletes beyond the pain threshold. However, there should be caution, since overdoing the LATT can lead to undesirable training states, critical levels of fatigue, and ultimately to overtraining. Therefore LATT should not exceed 1-2 workouts/week.

Maximum Oxygen Consumption Training (MVO2T)

During training and competition both parts of the oxygen transport system, the central (heart) and peripheral (capillaries at the level of the working muscle), are heavily taxed to supply the required oxygen. Since the supply of O2 at the working muscle lever represents a limiting factor in performance and since athletes with large MVO2 capacity have demonstrated better performances in endurance events, MVO2T must be an important concern for both coach and athlete.

Increased MVO2 results from an improved transportation of O2 by the circulatory system, and increased extraction and utilization of O2 by the muscular system. Therefore, a large portion of the training programme has to be dedicated to the development of MVO2. which is best served by work periods of longer duration 3-8 minutes or even longer, at 80-90% intensity (higher for shorter and lower for longer repetitions). The HR can be maximum or within ten bpm of maximum.

MVO2 may also be improved in training through shorter work periods (30 sec-onds-2 minutes) provided that the rest interval is short as well (10 seconds-1 minute). Under such conditions, training effect results not from one or two repetitions (which may primarily solicit the anaerobic system) but rather through the accumulative effect of several repetitions (4-12) which will reach MVO2.
Repeated work periods for MVO2 as well as the other methods could be performed in straight sets (i.e., 12 x 3 minutes, with RI=1:30 minutes) as well as in sets (i.e., 3×4 minutes with RI = 1:30 minutes while Rl between sets = 3 minutes). Since Rl between sets is longer, this more extensive restoration time allows more work to be performed. Similarly, since intensive (but wise) work is often equated with improvement, coaches should test which method is more productive for their athletes.

Anaerobic Threshold Training (AnTT)

The AnTT  refers to the intensity of an exercise at which level the rate of LA diffusion in the blood stream exceeds the rate of its removal. (AnTT = 4-6 mmol). Short repeated work periods stimulate the anaerobic metabolism, but the level of LA produced in the muscles does not rise significantly above normal levels. The LA diffuses into the adjacent resting muscles thus lowering its concentration level; it is metabolized in the working muscle; and also it is removed from the blood by the heart, liver, and muscles at the rate it is accumulated.

Therefore training program designed to reach the AnTT have to produce LA at the rate beyond the ability of the: above mechanisms to dispose of it. Such a program has to be around 60-90% of the maximum speed with a HR = 150-170 bpm. The duration of a work period can vary, but the work/RI ratio should be  1:1.

The AnTT is a trainable factor which can be expressed as a percentage of MVO2. For well trained athletes the AnTT can be reached at 85-90% of MVO2. (The intent of AnTT training is to elevate the threshold beyond 4 mmol, so that intensive work can be maintained without excessive accumulation of LA). During such training programs the subjective feeling of the athletes should be of mild distress and the speed just slightly faster than that of comfortable feeling.

Phosphate System Training (PST)

The intent of PST is to increase the ability of an athlete to be fast with less effort. PST should improve the propulsion off the starting blocks and in the early part of the event without using one s maximum speed. This is possible by applying short work periods of 4-15 seconds with a speed in excess of 95% of maximum.

Such a training program employs the phosphate energy system and, the outcome of it is the increase of the quantity of ATP-CP stored in the muscle as well as increasing the activity of the enzymes that release energy through the ATP-CP reaction.

Long recovery intervals between, work periods (work/RI ratio = 1:4-1:25) are necessary to ensure that the muscles CP supply is replaced completely. If the rest interval is shorter the restoration of CP will be incomplete and as a result anaerobic glycolysis rather than the phosphate reaction will become the major source of energy. This in turn will produce LA which will reduce speed and the desired training effect will not be realized. Therefore PST or sprint training should not cause muscle pain since this is a sign of anaerobic glycolysis.

Aerobic Threshold Training (ATT)

High aerobic capacity is decisive factor for all events of medium and long duration. Similarly it is also determinant for all sports where the O2 supply represents a limiting factor. Utilization of ATT is beneficial for the vast majority of sports since it enhances quick recovery following training and competition; develops the functional efficiency of the cardiorespiratory and nervous systems; and enhances the economical functioning of the metabolic system. Finally it also increases the capacity to tolerate stress for long periods of time.

ATT is performed mostly through a high volume of work without interruption (uniform pace) interval training using repetitions longer than 5 minutes and the pro-gressive elevation of intensity from a moderate to a medium fast speed within one training session.

The duration of an ATT session could be between 1-2.5 hours. The intended training effect may only be achieved where the LA concentration is between 2-3 mmol. With a HR of 130-150 bpm (sometimes even higher). Below these figures the training effect is questionable. During ATT the minute volume of blood is 30-40 litres while the O2 intake approximates 4-5.5 litres/minute.

ATT is often the primary training method for the preparatory phase. During the competition phase ATT may be planned 1-2 times/week as a method of maintaining the aerobic capacity, and as a recovery session(s) so that intensity is reduced but the general fitness level is maintained.

Building the program  Now that the five intensities of training have been illustrated, the critical question is how to incorporate them within a training prograrn. Traditionally a training program is designed by assigning certain physical, technical, or tactical objectives to certain days of a micro-cycle. Yet, the critical element in training is the training of the energy systems, which represents the foundation of good performance, in cooperation with the technicalAactical elements, based on knowledge of the physiological profile prevailing in a given event. Therefore When planning a micro-cycle, the coach should not write down the actual training content but father the mathematical values of the intensities needed in the cycle, which will suggest the components) of the energy systems to be emphasized in that particular training session (figures 110-114). The distribution per micro-cycle of the five intensities depends on the phase of training, the athletes’ needs, and whether or not a competition is planned at the end of the cycle. Therefore, as suggested by figures 110-114, when planning a micro-cycle the coach should first determine the five values in terms of percentages, and then distribute the values per days to meet the decided proportion.

Training the Energy Systems: The Five Intensity Values

Figure 109. A summary of the effects of the five intensitics on training the energy systems (made by Alan Roaf, 1988).

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