Metabolic Fatigue Research Paper

Muscle fatigue, or physical fatigue, is the decline in ability of a muscle to generate force. It can be a result of strenuous exercise but unusual fatigue may be caused by interference with the different stages of muscle contraction. There are two main causes of muscle fatigue, nervous fatigue and metabolic fatigue.
Nervous Fatigue
Nervous fatigue is the decline in the ability of a nerve to sustain a signal resulting in innervation of the muscle. The muscle's ability to generate force is most strongly limited by nerve's ability to sustain a high-frequency signal. After a period of maximum contraction, the nerve's signal reduces in frequency and the force generated by the contraction diminishes. Nerves are responsible for controlling the contraction of muscles. For extremely powerful contractions that are close to the maximum limit of a muscle's ability to produce force, nervous fatigue can be a limiting factor in untrained individuals.
Metabolic Fatigue
By contrast, metabolic fatigue is the result of a decrease in necessary ions or substrates, or the buildup of metabolites, such as lactic acid. Lactic acid accumulates as a result of anaerobic exercise, anaerobic exercise is when the exercise if focused around short powerful bursts of energy where endurance is not needed, typically requires less oxygen to perform.
Substrates produce metabolic fatigue by being depleted during exercise, resulting in a lack of energy sources to fuel contractions. Accumulation of metabolites can directly or indirectly produce metabolic fatigue within muscle fibers through interference with the release of calcium from the sarcoplasmic reticulum or through reduction of the sensitivity of contractile molecules actin and myosin to calcium.
Temperature can greatly affect the ability of your muscle to contract.
It is more difficult for muscle to contract in cold temperatures than in warmer ones. Temperature affects the ease with which oxygen is released from hemoglobin. At cold temperatures, oxygen is more tightly bound to the hemoglobin and does not release as easily. This slower rate of release leads to a lower amount of oxygen available to your muscles, making contraction more difficult, this makes your muscles feel stiff. The opposite is true in warm temperatures; oxygen readily releases from hemoglobin, giving a steady supply of oxygen and allowing your muscles to contract
easily.
To begin muscle contraction, the muscle receives an impulse from the spinal cord. The impulse then travels down the motor neuron and reaches a neuromuscular junction where it releases acetylcholine. The Impulse continues through the sarcolemma and branches down the t tubules that surround the myofibrils. As the impulse passes down the t tubules the sarcoplasmic reticulum surrounding the t tubule to release calcium ions into the sarcoplasm eventually reaching the sarcomere. The Calcium ion binds to the troponin on the actin which causes tropomyosin to move and expose binding sites for myosin. The myosin head now binds to actin and forms a cross bridge. ADP and Pi are released from the myosin which causes it to move and perform the power stroke. ATP binds to myosin to release the actin and allows the myosin to form another cross bridge and continue the cycle of contraction until the impulse stops. One the impulse is over the calcium ion is released from the troponin causing tropomyosin to cover the binding sites again and prevent contraction. The calcium ions return to the sarcoplasmic reticulum and waits for another impulse.