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Exercise Physiology 1: General Information

This page provides basic exercise physiology information. The skater who wishes much more extensive coverage of the subject is referred to Stephen Seiler's Site.

Athletic Performance Model

The first figure below shows Seiler's model of athletic performance and velocity in particular. This figure indicates the areas which contribute to your speed. I will discuss the broader issues and not get into details like mitochondria.

Energy Systems

Where does your body get the energy it needs for racing? Three energy systems are discussed: Aerobic, Anaerobic, and ATP-CP.

Aerobic

Aerobic conditioning and Max VO2 training: Aerobic conditioning is not the same as increasing Max VO2 (VO2MAX is discussed in detail at the bottom of this page. At this point consider it as the most oxygen your body can utilize) . The bulk of your training is for aerobic conditioning. This is low intensity training that will accomplish various physiological adaptations crucial for performance improvement. These adaptations are


Max VO2 training will occur in the Race Phase and be accomplished by hard efforts above the Anaerobic Threshold. Exercise at this level increases the amount of oxygen you can consume during all out efforts. The greater the amount of oxygen consumed, the greater potential for improved performance.

Anaerobic

Anaerobic metabolism or glycolysis occurs when the level of muscular activity causes the demand for oxygen to exceed the body's ability provide it. In the absents of oxygen, the body will produce energy but at a cost. The waste product of anaerobic metabolism is lactic acid. The more intense the exercise, the faster that lactic acid is accumulated in the muscles and blood. Anaerobic metabolism is responsible for the majority of energy production in all-out efforts lasting approximately 1 to 10 minutes. The point at which lactic acid begins to quickly accumulate in the blood is known as the anaerobic threshold or Lactic Threshold (LT).

A critical point needs to be made regarding the anaerobic threshold. The closer you can get your anaerobic threshold to your Max VO2, the faster you will become. Simply having a high Max VO2 does not necessarily make you fast. Being able to sustain an effort close to your Max VO2 is what will determine whether you are fast or not.

Lactic acid interferes with the muscles ability to contract. The burning sensation experienced with the accumulation of lactic acid is the result of a change in muscular acidity. The ability to tolerate and buffer the effects of this changing acidic environment is what anaerobic training is all about.

ATP-CP

ATP (adenosine triphosphate) and CP (creatine phosphate) are the substances used for cellular activity in all tissues, including muscle. This is the energy stored in muscles and available immediately for use by the muscles in contraction and relaxation. A limited amount of ATP can be stored in muscles. When the intensity of effort is maximal, this energy source is depleted in 20-30 seconds. After this time, intensity must decline or the effort must stop. ATP must be continually replenished during physical activity. This energy system would come into play with climbing a short, steep hill or sprinting. Training this energy system requires very short bouts of all-out effort (10-15 sec) with long and probably complete recovery between efforts. Care must be taken not to stimulate the anaerobic energy system with it's production of lactic acid. The objective of training this system is to deplete the ATP and CP stores thus stimulating a compensatory increase in ATP and CP stores. Additional neuromuscular conditioning causes this system to respond quicker. Creatine Monohydrate supplements (which yield CP) are commonly available in health food stores now. ATP supplements can also be obtained but the efficacy is debateable.
The figure on the left above shows how different physical activities utilize the three energy mechanisms. The figure on the right shows how an Olympic cyclist was able to modify his lactate threshold and drop his race time by 4 minutes through training and aerodynamic changes.

Lactic Acid


Lactic acid buildup ( acidosis) can cause burning pain, especially in untrained muscles. Lactic acid accumulation can lead to muscle exhaustion withing seconds if the blood cannot clear it away. A strategy for dealing with lactic acid buildup is to relax the muscles at every opportunity, so that the circulating blood can carry the lactic acid away and bring oxygen to support aerobic metabolism. ...much of the lactic acid is routed to the liver, where it is converted to glucose. A little lactic acid remains in muscle tissue, where it is completely oxidized when the oxygen supply is once again sufficient.

Heart Rate vs. Age

The above figure shows the safe (green), caution (yellow), and danger (red)heartbeat rate zones for a typical person of the age on the bottom scale. A stopwatch or heartrate monitor can be used to determine your exercise heart rate.
Your maximum heart rate is very useful because your VO2MAX is correlated with the heart rate. as shown above. Consequently you can use a stopwatch or heartrate monitor to observe increases (or decreases) in your VO2MAX. To get an absolute VO2MAX you will need specialized medical/sports equipment but you can get a relative reading using the heartrate method with a stopwatch.

VO2 Max Defined

VO2 max is the maximum volume of oxygen consumed by the body each minute during exercise, while breathing air at sea level. Because oxygen consumption is linearly related to energy expenditure, when we measure oxygen consumption, we are indirectly measuring an individual's maximal capacity to do work aerobically. "What are the determinants of VO2 max?" Every cell consumes oxygen in order to convert food energy to usable ATP for cellular work. Muscle cells that are contracting have high demands for ATP. So it follows that they will consume more oxygen during exercise. The sum total of billions of cells throughout the body consuming oxygen, and generating carbon dioxide, can be measured using volume-measuring and oxygen-sensing equipment. The muscle's capacity to use oxygen exceeds the heart's capacity for delivery. Long term endurance training can result in a 300% increase in muscle oxidative capacity, but only about a 15 to 25% increase in VO2 max. VO2 max can be altered artificially by changing the oxygen concentration in the air. VO2 max can be dissociated from skeletal muscle characteristics.

Heart stroke volume, in contrast, is linearly related to VO2 max. Training results in an increase in stroke volume and an increase in maximal cardiac output. Greater capacity for oxygen delivery is the result. More muscle can be supplied with oxygen simultaneously while still maintaining necessary blood pressure levels. Heart performance dictates VO2 max. In general, absolute VO2 max favors the large endurance athlete, while relative VO2 tends to be higher in smaller athletes. For comparison, the average maximal oxygen consumption of an untrained male in his mid 30s is about 40-45 ml/min/kg, and decreases with age. The same person who undergoes a regular endurance exercise program might increase to 50-55 ml/min/kg. A champion male masters runner age 50 will probably have a value of over 60 ml/min/kg. An Olympic champion 10000 meter runner will probably have a value approaching or over 80 ml/min/kg!

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