Understanding Lactate Threshold Training and V02 Max Training

In order to understand what lactic acid is and the role it plays in fueling our running activities, it will help to have a basic knowledge of the three ways our bodies produce energy. There are three basic systems. They are ATP-PCr, glycolytic and oxidative. Lactic acid is a major player in glycolytic and oxidative systems

The ATP-PCr system is the simplest of the three. This system uses a molecule called phosphocreatine to produce energy very quickly and without the use of oxygen. There are very small stores of this substance in your body, so it can be used only for a short duration, high intensity events such as sprinting. There is only enough stores of phosphocreatine in your body to fuel up to about 15 seconds of energy during an all out sprint.

The glycolytic system produces energy from the breakdown of glucose. Glucose comes from the digestion of carbohydrates that you eat and also from glycogen (a storage form of glucose) in your liver. Glucose accounts for 99% of the sugar in your blood. The process involves 12 highly complex reactions that taken together are called glycoysis. Glycolysis eventually produces a substance called pyruvic acid and contributes a small amount of energy. This entire process can take place without the presence of oxygen.

The oxidative system picks up where the glycolytic system leaves off. When your body can supply a sufficient amount of oxygen to its working muscles, most of the pyruvic acid produced during glycolysis enters a series of reactions called the Krebs cycle. This cycle produces 90% of the energy to sustain medium to long term exercise. However, the Krebs cycle only works when you are exercising at an intensity at which your body can supply sufficient amounts of oxygen to your muscles. When exercise reaches very high intensities, such as sprinting or 400-800m races, your body's need for energy exceeds your ability to provide an adequate supply of oxygen to your muscles. At this point, your body must rely on the shorter term of ATP-PCr and glycolytic systems.

Now, we are finally getting to lactic acid. Recall that glycolysis ultimately produces pyruvic acid. As mentioned earlier, much of the pyruvic acid enters the Krebs cycle and is used to produce large amounts of energy. The pyruvic acid that remains is converted into lactic acid. When you are exercising at an easy pace, small amounts of pyruvic acid are produced. Your body easily handles this substance and small amounts of lactic acid are produced. As your workout becomes more intense, glycolysis really heats up and you start to produce very large amounts of pyruvic acid. All of this pyruvic acid starts to back up and a large amount of lactic acid is produced as a result.

According to earlier beliefs, this build up of lactic acid was a waste product that caused fatigue, burning muscles and could only be cleared during rest and recovery.Now, we know that most of the lactic acid produced is used to produce immediate energy for your muscles and also plays an important part in generating additional glycogen to be used for energy. Lactic acid is not only produced during highly intense bouts of exercise. It is produced at all times, even at rest. A recent study showed that even during low intensity exercise, as much as 50% of the glucose that is converted to energy during glycolysis is converted to lactic acid. Our muscles produce lactic acid, but they also use lactic acid. Many studies have confirmed that approximately 75% of lactic acid is removed from our bloodstreams through oxidation. That is, it is converted to energy and used to fuel our muscles. The remaining 25% is cleared by conversion to glycogen which is used to produce further energy.

So, how does lactic acid produce energy? An important piece of this puzzle is the lactate shuttle which was introduced in 1984. The original lactate shuttle hypothesis had the ff. definition: " the shuttling of lactate through the interstitium and vasculature provides a significant carbon source for oxidation and gluconeogenesis during rest and exercise". In other words, lactic acid moves freely in and out of muscle cells to provide quick energy and also to produce glycogen.

Recall that during low intensity exercise your body is supplying enough oxygen to your muscles to easily clear the pyruvic acid and lactate produced. When you increase your speed to a moderate or hard pace, your enry demands increase. Glycolysis starts to heat up and lactate produce a lot of pyruvate. The pyruvate starts to pile up and as a result, more and more lactate is produced. Eventualy, you reach a speed where your production and usage of lactate is in balance. You are producing a lot of lactate, but are using an equal amount of energy. This is considered as your lactate threshold or anaerobic (without oxygen).

Apart from sprinters (100-200m) almost every distance will benefit from training to improve their lactate threshold. V02 max is mostly genetically determined but can be trained up to 15-20% higher. Lactate threshold, on the other hand, can be improved significantly by everybody. Most sedentary people have a lactate threshold of 50-55% of their V02 max whilst in trained people it can exceed 90& V02 max. It is also a great predictor of performance. Running speed at your lactate threshold is one of the best predictors of ultimate performance in events ranging from 3K through the marathon.

The best way to improve threshold training is to do some running at or slightly abouve your lactate threshold pace. This can be done in intervals or in threshold (tempo, fast continuous, AT) runs. If you run slower than your lactate threshold pace then you won't build up much lactate and so your body won't get used to running it or using it. If you run too fast, then you will be far beyond your lactate threshold and you will either improve your V02 max or only improve your sprinting. The trick then is to run just at the right speed to give your lactate threshold a little nudge. Improving your lactate threshold is a quick way to get faster. It is a factor that you can improve a long way from untrained and you don't have to run fast to improve it.

V02 max means the maximal volume of oxygen we utilise per pound of body weight. It tells us ur performance potential. The more we can use the faster we can potentially go. The physical limitations that restrict the rate at which energy can be released aerobically are dependent upon:

1. the chemical ability of the muscular cellular tissue system to use oxygen in breaking down fuels,

2. the combined ability of the cardiovascular and pulmonary systems to transport the oxygen to the muscular tissue system.

"The use of the training heart rate and emphasis on cardiovascular effects of training has diverted atention from the true target of training, skeletal muscle. Training is specific to the muscle fibers used in an activity. Training does not transfer well from one activity to another", according to Dr. Brian J. Sharkley. To accurately measure endurance improvement, athletes should be tested while they are engaged in an activity similar to the sport or activity in which they usually participate. For most athletes, V02 max values are substantially higher during their sport-specific activity. Maximal oxygen consumption levels depend on genetic limits. This shuld not be taken to mean that each individual has an exact V02 max that cannot be exceeded. Both genetic and environmental factors influence V02 max values. The genetic factors probably establish the boundaries for the athlete, but endurance training can push V02 max to the upper limit of these boundaries.

(Sources: www.exercisestandards.org, www.runningonline.com)