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Having looked last time at the creatine phosphate system, which we use for short maximal bursts, today we will look at the second energy system down, the lactate system. Like the creatine system this energy system makes energy without oxygen:if the intensity during aerobic exercise becomes greater that the aerobic system can provide for it will take over. Similarly when near maximal exercise lasts longer that the CP system can provide for it will take over.
The conversion of glucose to lactic acid is occurring constantly in the body and only becomes a problem when lactic acid starts to to accumulate. If the lactic acid production and removal are equal then there is no problem, but if the production of lactic acid exceeds the muscles and cardiovascular system’s ability to disperse it there will be a build up of this lactic acid which will eventually cause the cessation of the activity. This is known as the onset of blood lactate accumulation (OBLA). It is associated with sensations of laboured breathing, heavy limbs, pain and aches in the muscles which together will cause the exercise to stop. These sensations are in fact a result of increased hydrogen ions that are a result of this excess lactic acid.
Targeted interval training will improve the body’s ability to withstand the build up of lactic acid (known as lactic tolerance) and/or to remove it more quickly thus preventing this accumulation. This anaerobic training (the dreaded anaerobic intervals!!) quickly uses up the glycogen stored in the muscles and liver (our fuel tank) and requires short periods (1-3 minutes) of strenuous activity followed by periods of recovery. Ideally this recovery should be active (for example walking or slow jogging between faster running or rowing gently between harder intervals to aid return of blood back to the liver. By contracting muscles in this recovery mode you are helping to squeeze blood back up the arteries through clever one way valves, so your heart does not have to do it all on it’s own! This is why after a brutal interval your personal trainer should force you to walk or move about even if you really only feel like flumping down.
This second energy system is one of the most important in many sports, from squash, rowing, rugby, tennis and boxing. These are the activities where we need up to 95% of maximal energy but also for a sustained periods of a few minutes. So a rally at tennis followed by a break for serve, a passage of play in rugby followed by a penalty and so on. The short duration of the lactate system is particularly challenged by rowing, where a typical race is 2000m or 6 to 7 minutes. The energy system used is the lactate one, but it is asked to go beyond the time at which it runs out. So the first 3 minutes is fine, it’s the next 3 in which your body will be screaming to stop but your mind must make it carry on. This also explains why of all the Olympic sports the rowers are the ones that collapse after a race. I too have too adopt the foetal position after a good 2k time. this is why interval training is so important for fitness gains.