What are the four possible energy sources for a muscle and three of ATP contraction?

Four possible energy sources for a muscle:

- Adenosine triphosphate (ATP): ATP is the primary source of energy for muscle contractions. It is produced by the breakdown of glucose and other fuels in the body's cells.

- Creatine phosphate: Creatine phosphate is a molecule that stores high-energy phosphate bonds. It is used to rapidly regenerate ATP during muscle contractions.

- Glycogen: Glycogen is a polysaccharide that stores glucose molecules in the liver and muscles. It can be broken down to release glucose, which can then be used to produce ATP.

- Fatty acids: Fatty acids are a type of lipid that the body stores in adipose tissue. They can be broken down to release energy that can be used to produce ATP.

Three types of ATP contraction:

- Eccentric contraction: This is when a muscle lengthens while generating force. This occurs when a muscle is overpowered by a load.

- Concentric contraction: This is when a muscle shortens while generating force. This occurs when a muscle lifts a load.

- Isometric contraction: This is when a muscle generates force without changing its length. This occurs when a muscle holds a load in a fixed position.