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Muscle fatigue is not the same as muscle weakness, though weakness is an initial symptom. Despite a normal amount of force being generated at the start of activity, once muscle fatigue has set in and progressively worsens, if the individual persists in the exercise they will eventually lose their hand grip, or become unable to lift or push with ...
Abnormal muscle fatigue (premature fatigue and/or inability to get into second wind), muscle pain (myalgia), cramping or muscle stiffness during and/or after exercise, [citation needed] Shortness of breath , or rapid breathing , or heavy breathing , or both (exercise hyperventilation) [citation needed]
Mitochondrial myopathies are types of myopathies associated with mitochondrial disease. [1] Adenosine triphosphate (), the chemical used to provide energy for the cell, cannot be produced sufficiently by oxidative phosphorylation when the mitochondrion is either damaged or missing necessary enzymes or transport proteins.
The onset of acidosis during periods of intense exercise is commonly attributed to accumulation of hydrogens that are dissociated from lactate. Previously, lactic acid was thought to cause fatigue. From this reasoning, the idea of lactate production being a primary cause of muscle fatigue during exercise was widely adopted.
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
The muscle weakness that worsens with activity (abnormal muscle fatigue) in myasthenia gravis [66] is a symptom shared by other neuromuscular diseases. Most of the metabolic myopathies, such as McArdle disease (GSD-V), have abnormal muscle fatigue rather than fixed muscle weakness.
It was once believed that lactic acid build-up was the cause of muscle fatigue. [14] The assumption was lactic acid had a "pickling" effect on muscles, inhibiting their ability to contract. The impact of lactic acid on performance is now uncertain, it may assist or hinder muscle fatigue. [citation needed]
However, this appears likely only when lactate levels are very high. Elevated lactate levels are only one of many changes that occur within and around muscle cells during intense exercise that can lead to fatigue. Fatigue, which is muscle failure, is a complex subject that depends on more than just changes to lactate concentration.