The “Anaerobic Threshold” test involves gradually increasing the amount of work done by the individual and measuring the amount of lactate accumulated in the blood at the end of each work stage. You heart rate is also measured at the end of each stage so as to match heart rate with lactate accumulation level.
The body produces energy for exercise using two predominant systems. These are the aerobic (with oxygen) and the anaerobic (without oxygen) systems. The end product of aerobic metabolism is carbon dioxide and water, both of which the body and easily dispose of. A product of anaerobic exercise is lactic acid (or lactate), which has a negative effect on the energy production systems. In this test the amount of lactate in the blood is measured.
At lower intensities of exercise the predominant energy production system used is the aerobic system. As exercise intensity increases, the greater the contribution of the anaerobic system. One is able to work at increasing intensities relying predominantly on aerobic metabolism until a point is reached where the contribution of anaerobic metabolism becomes too great for the muscle to cope with the detrimental effects of the lactic acid produced. At this point the rate of accumulation of lactate in the blood accelerates as shown on the graph of your test results. Aerobic, or endurance, training should not exceed this level of intensity, i.e. not exceed the anaerobic threshold heart rate (estimated below).
For endurance exercise, the fuel being used for energy production is important. The greater the contribution of fat to power exercise, the longer the exercise intensity can be maintained. This is termed “glycogen sparing”. Low-intensity training of long duration increases the body’s ability to mobilise and metabolise fats. To increase the ability to use fats the major proportion of a training schedule should be at your “aerobic threshold” heart rate, with one or two sessions being close to “anaerobic threshold”.
With this type of training you will gain an increased ability to metabolise fat and an increased ability to work aerobically at higher intensities of exercise. You will be able to run harder, or faster, at the same heart rate and before the accumulation of lactate in the blood accelerates. This will be indicated by a rightward shift of the heart rate and blood lactate concentration curves as depicted graphically on the attached sheet.
When training for the shorter endurance events where glycogen (carbohydrate stored in muscle) will remain the predominate fuel, approximately two medium intensity sessions at the anaerobic threshold should be performed per week. One should be just above anaerobic threshold to increase the stress on the lactate clearance systems and increase lactate tolerance, with the other session being of greater volume but at the lower intensity aerobic threshold.