nergy production, is occurring during the relef intervals?
During the relief intervals, a portion of the muscular stores of ATP and PC that were depleted during the preceding work intervals will be replenished via the aerobic system. In other words, during the relief intervals, part of the rapid recovery phase is complete. In addtion, a portion of the O2-myoglobin stores will also be replenished. Thus, during each run that follows a relief interval, the replenished ATP and PC and O2 myoglobin stores will again be available as an energy source. Consequently, energy from the LA system will be “spared,” so to speak, by that amount, and lactic acid will not accumulate as rapidly or as great an extent. In contrast, during a continuous run the phosphocreatine (PC) in the ATP-PC system will be exhausted within a matter of several seconds and will not be replenished until the work is termintated. In this case, energy in the form of ATP from the LA system will be called on early in the run, and LA will rapidly accumulate to high levels.
All this has real meaning when applied to training, for the savings in fatigue accompanying intermittent work can be converted to an increase in the intensity of work performed. This is the single most important feature of intermittent work and as such is the key to the interval training system. An intermittent work level as much as two and one-half times the intensity of the continuous level can be performed before blood lactate acid levels in each are comparable. The interaction between the ATP-CP and the LA systems during intermittent work also varies slightly according to the type of activity level of the relief interval used. This discussion has been centered on intermittent work using complete rest intervals. During actual interval training, the relief intervals should consist of either light or mild work. Later, you will learn when it is best to use one or the other. Right now, the primary difference between intermittent work of the same intensity and duration performed with complete rest intervals as compared with light or mild work-relief intervals is that the blood lactic acid levels will be higher with the latter. This is so because the work performed during the relief interval blocks or partially blocks the replenishment of the ATP-PC stores. Without as much of these stores being renewed, a greater proportion of the energy needed during the work intervals must be supplied via the LA system. In this way, the accumulation of lactic acid willb e greater, the harder the work during the relief interval, the greater will be this lactic acid accumulation.
Specifically, in the development of the energy systems, intermittent work or the interval-training system accomplishes the following:
1. It allows the stores of ATP + PC to be used over and over. This, in turn, provides an adequate stimulus for promoting an increase in the energy capacity of this system and aids in delaying the onset of fatigue by not delving so deeply into anaerobic glycolysis.
2. With proper regulatin of the duration and type of relief interval, the involvment of anaerobic glycolysis will be maximal and thus improved.
3. By performing longer work intervals with many repetitions and brief relief intervals, the oxygen transport sytem is stressed and the aerobic energy system is improved.
Daryl Conant, M.Ed