Another source that triggers the release of insulin is ATP. ATP is the abbreviation for adenosine triphosphate. ATP is the main energy transfer molecule that is contained in a cell. ATP is made from ADP or AMP. ADP is abbreviation for adenosine diphosphate and AMP is the abbreviation of adenosine monophosphate. ATP is being continuously recycled in the human body. The cell has to release energy from the chemical bonds that it is stored in molecules. The phosphates in a molecule are like poles of a magnet that are continuously repelling each other and when a molecule looses a phosphate it is immediately converted into energy. The human body has millions of ATP cells that provide the energy for muscle contractions. Some of the energy is lost in heat that is generated by the muscles during a workout. After ATP has been consumed energy and creatine are required to replace the phosphate that was lost. The electron chain that fuels the reaction in the molecules to produce ATP or energy is done by breaking down glucose. All carbohydrates that are taken eventually become glucose in the body.
The glucose used to be converted into energy comes from one or two places. Carbohydrates that have been converted and stored as glycogen are converted to ATP. The second source that produces ATP during any strenuous exercise like a workout comes from mitochondria. Excess ATP is produced when exercising or lifting heavy weights. After a workout session the extra ATP that is circulating in the body trigger the release of insulin. The insulin then counters the excess sugar that has been released into the bloodstream. Secondly insulin signals the mitochondria to stop producing ATP. Once the ATP production slows down the body starts to repair of muscles. Long workout sessions are not going to help as there is not enough energy left to trigger muscle growth. So there is really no point in pushing the body beyond its limits as that is going to damage and not help the body. A workout should only be enough to push the body to its maximum but not over it.