Final answer:
Muscle fatigue is primarily caused by the depletion of ATP, which is required for muscle contraction, and the buildup of lactic acid which affects pH levels. Other contributors include imbalances in electrolytes disrupting calcium flow and damage to muscle structures from prolonged exertion.
Step-by-step explanation:
What contributes to muscle fatigue? The answer is that during muscle contractions, ATP (Adenosine Triphosphate) is depleted, leading to muscle fatigue. As muscles work, they consume ATP, which is essential for muscle contraction.
Additionally, lactic acid builds up due to anaerobic respiration when the muscles are heavily used. The accumulation of lactic acid leads to a decrease in intracellular pH, which negatively affects the enzymes and proteins involved in muscle contractions.
Also, disruptions in the balance of sodium (Na+) and potassium (K+) across the muscle membrane can impair the flow of calcium (Ca++) from the sarcoplasmic reticulum (SR), which is crucial for muscle contraction. Prolonged exercise can damage the SR and the sarcolemma, leading to further issues with calcium regulation. Therefore, a lack of ATP along with other factors contributes to muscle fatigue.