Energy Systems


Alactic Energy

The alactic component of the anaerobic energy system relates to the production of energy without the additional production of lactic acid.  Alactic energy is synthesized through the use of phosphagen, phosphocreatine, and muscular adenosine triphosphate or ATP (Gastin, 2001).  Alactic energy is used concurrently from the start of a sprint until an approximately maximal duration of 30 seconds.  The initial block start or “initial thrust” of a race is characterized by the sole use of “stored muscular ATP.” Additionally, this initial thrust out of the blocks is coupled with the use of phosphocreatine for movement of each leg at top speed. 

As muscular ATP supply only lasts for approximately two seconds, after the start and first few steps of a high intensity sprint, it is largely depleted.  The remaining portion of the alactic energy stage is characterized by the use of the phosphocreatine system and the extended phosphocreatine system. 

Phosphocreatine is largely used for 15 seconds of a high intensity sprint. This includes the acceleration and maximum velocity stages of a sprint.  The extended phosphocreatine system occurs largely from 15 seconds until 30 seconds of a race and is characterized by an individual’s ability to maintain a high capacity for speed—also known as“speed endurance”— and the initial interaction with lactate production (Wells, Smith, & Taylor, Training Energy Systems, 2001).

(Wells, Smith, & Taylor, 2001)

(Wells, Smith, & Taylor, 2001)

Lactic Energy

The lactic component of the anaerobic energy system relates to the production of energy through the process of glycolysis and the subsequent production of lactic acid.  This process occurs through the “breakdown of carbohydrates, mainly in the form of muscle glycogen, to pyruvic acid and then lactic acid” (Gastin, 2001).  In youth or inexperienced athletes, glycolysis can occur before the thirty second mark of a race, affecting an athlete during speed endurance components of a race. 

The lactic system is the key component of a race lasting between 30 seconds and 45 seconds.  During this phase, lactic acid begins to accumulate and between 45 seconds and 90 seconds, athletes are forced to maintain and hold speed with elevated levels of lactic acid.  Following a maximum duration of 90 seconds, continued lactic acid production is coupled by aerobic systems of respiration (Wells, Smith, & Taylor, Training Energy Systems, 2001).