Anaerobic & Aerobic Energy Systems Virginia PE SOL 10.2 Anatomical Basis of Movement

Anaerobic vs. Aerobic Anaerobic Activity: Short lasting, high-intensity where your body’s supply for oxygen exceeds the oxygen supply available. Aerobic Activity: Low to high intensity activity where the body relies on the aerobic energy system (oxygen present).

Fast Twitch vs. Slow Twitch Muscles People have two general types of skeletal muscle fibers: slow-twitch (type I) and fast-twitch (type II). Slow-twitch muscles help enable long-endurance feats such as distance running, while fast-twitch muscles fatigue faster but are used in powerful bursts of movements like sprinting.

Fast-Twitch Activities

Slow-Twitch Activities

The ATP-PC Energy System High Power/Short Duration ATP and phosphocreatine (PC) compose the ATP-PC system, also sometimes called the Phosphogen system. It is immediate and functions without oxygen. It allows for up to approximately 12 seconds (+ or -) of maximum effort. During the first few seconds of any activity, stored ATP supplies the energy. For a few more seconds beyond that, PC cushions the decline of ATP until there is a shift to another energy system. Examples: a short sprint, lifting a heavy resistance for three repetitions, or pitching a baseball.

ATP is made up of ADP + PC

The Glycolytic System Moderate Power/Moderate Duration Now it becomes more complicated as energy demands shift to this system. The glycolytic system is the “next in line” tool after the ATP- PC system runs its course. Dietary carbohydrates supply glucose that circulates in the blood or is stored as glycogen in the muscles and the liver. Blood glucose and/or or stored glycogen is broken down to create ATP through the process of glycolysis. Like the ATP-PC system, oxygen is not required for the actual process of glycolysis (but it does play a role with the byproduct of glycolysis: pyruvic acid).

Fast Glycolysis Here is where it gets interesting. After maximum power declines around 12 seconds, further intense activity up to approximately 30 seconds results in lactic acid accumulation, a decrease in power, and consequent muscle fatigue. This high, extended effort is labeled “fast” glycolysis. Exerting further effort up to approximately 50 seconds results in another drop in power due to the shift in dependence on the oxidative system. Bottom line: it is getting tougher. In fast glycolysis, more power can be generated, but pyruvic acid is converted to lactic acid and fatigue ensues quickly Example: think of an all-out sprint, to a slower jog, to an eventual walk. That is the progression of the three energy systems when going all-out.

Slow Glycolysis Let’s enter “slow” glycolysis into the discussion (warning: more science jargon ahead, but hang in there). Recall the byproduct of glycolysis is pyruvic acid and in fast glycolysis, more power can be generated, but pyruvic acid is converted to lactic acid and fatigue ensues quickly. Slow glycolysis is different. Relatively less power is generated, but pyruvic acid is converted to acetyl coenzyme A (acA), fed through the oxidative Krebs cycle, more ATP is produced, and fatigued is delayed. Thus, extreme fatigue can be avoided (but relatively less-intense effort can continue to be expressed) in slow glycolysis as compared to fast glycolysis. Examples: any moderately-long runs such as yards, a 1:30 effort of all-out MMA maneuvers, or a one-minute full-court press - offense display - and another full-court press effort in basketball

The Oxidative System Low Power/Long Duration Your maximal effort was fueled initially by the ATP-PC, but your performance declines. Continued effort results in further decline, either via fast glycolysis (quick decline) or slow glycolysis (slower decline). You’re now entering the complex world of the low power but longer duration oxidative system. Examples: 6-mile run, low-level manual labor on an eight-hour work shift, or a 3-mile walk.

Lactic Acid System The other system that does not require the presence of oxygen to resynthesize ATP in muscles is the lactic acid system, which is also known as anaerobic glycolysis. Following the initial seconds of maximal exercise, PC stores are exhausted and ATP still needs to be produced to provide energy. Fatigue & Exhaustion occur when lactic acid accumulates in the muscle cells.

Antagonist & Agonist Muscles Agonist Muscle is the muscle(s) that provides the major force to complete the movement. Antagonist Muscle is a muscle that opposes the action of another muscle. Example: Bicep and Triceps