Understand the Science

Our body taps into three forms of energy: two anaerobic and one aerobic. The two anaerobic (“without oxygen”) energy systems are the phosphocreatine system and the anaerobic glycolysis system:

• The phosphocreatine system harnesses the energy that is stored in the muscles themselves. This energy source lasts only a few seconds.
• Anaerobic glycolysis uses carbohydrates (glucose and glycogen) that are stored in the liver, blood and working muscles. This energy source is also short-lived, lasting only a few minutes.
• The aerobic (“with oxygen”) system is called aerobic glycolysis or fatty oxidation cycle:
• Aerobic glycolysis (fatty oxidation cycle) uses oxygen to change fat and carbohydrates into performance. This energy source can last for hours.
• Whenever we perform sustained exercise, our bodies utilize all three systems simultaneously. However, the body relies on some of these energy systems more than others as intensity and duration of exercise fluctuate.
• As exercise becomes more intense, the body utilizes the anaerobic energy system more and becomes less aerobically efficient. While training at this level has many important benefits (it improves muscular development and increases speed), it cannot be sustained for long durations. When you design your training program and race strategy, knowing the precise moment your body becomes less aerobically efficient can help you boost your sports performance.

VO2 max is an accurate measurement of how efficiently the cardiovascular system delivers oxygen to working muscles. It also measures how well those muscles use the oxygen during peak intensity. It is used as an effective measurement of overall aerobic capacity and endurance. Through vigorous training, you can see measurable improvements in your V02 max over time. However, overtraining can lead to a decline in V02 max levels.

Lactic acid was once considered the culprit responsible for the muscle soreness and fatigue that occur 1-3 days after prolonged or high intensity exercise. Science has now shown that lactic acid clears from the blood within an hour after completing exercise and is actually the ideal fuel for the body. Learning how to harness that fuel through lactic acid threshold training is an important method to improve endurance performance.

Lactic acid is the product of the anaerobic metabolism and is used as a fuel for the aerobic metabolism (fatty oxidation metabolism). As workload and intensity increase, the body begins to produce more lactic acid than it can utilize. Lactic acid threshold is an inflection point reached when the body out-produces its ability to clear lactic acid from the blood. After achieving this threshold, it becomes more difficult to sustain the same or a greater intensity workout.

Tracking the changes in lactic acid threshold over the course of multiple tests can show whether a training program is effective in making your body a more aerobically efficient machine. It can also be utilized to target the best training and racing intensities.