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Before we talk about determining blood lactate levels, we need a deeper understanding of the energy producing systems at play, as well as some commonly used terminology.

There are 2 main systems for producing energy in the body, the aerobic system and anaerobic system. There is a 3rd system, the Creatine Phosphate system, which provides energy for very short bursts of a few seconds, or until your creatine phosphate stores are depleted. we will concentrate on the 2 main ones.

The aerobic system or aerobic metabolism, utilizes oxygen, using predominately fats & some carbohydrates for energy along with recycled lactate which is produced at low levels and metabolized efficiently. This is your endurance energy system. You may still have recurring nightmares about this from freshman biology, also known as the Krebs (or Citric Acid) Cycle

Your lactate threshold(LT) is a highly aerobic point where lactate levels in the blood are still low but just starting to reach steady state levels. Your LT is the most efficient effort level that you can sustain for long periods of time without going in to your energy reserves (i.e. glycogen). Beyond this point, you are exceeding your ability to recycle lactic acid back into the Citric Acid Cycle and lactate levels begin to rise; changing local blood pH and affecting local chemical reactions.

The anaerobic system does not utilize oxygen, using predominantly carbohydrates for energy. An efficient anaerobic system will produce a lot of lactic acid as its by-product. As you know, in large amounts, this causes the burn and fatigue you often feel when working hard. Thus, your anaerobic threshold (AT) is much more stressful and is therefore only sustainable for shorter periods of time.

What does this mean?

For the endurance athlete, the BALANCE of these two systems must be developed optimally for their chosen event. Performing a lactate test (to be discussed in another post) will help determine the relative contribution of each system. In general, the well-developed endurance athlete will produce very little lactate even at high speeds. Endurance sport athletes, such as cyclists, Ironman athletes, triathletes and top marathon runners need to be highly aerobic, which means that very little lactate is produced even at peak speeds and testing reveals a very flat lactate curve. Most of their energy comes from aerobic sources.

Optimizing lactate threshold development is the main goal of endurance training, and racing at or near LT proves the most efficient route to a solid race day performance.

So, how can you use this information for training? Watch for an upcoming post on Lactate testing.