A 19-year-old athlete reports prolonged muscle stiffness and…
A 19-year-old athlete reports prolonged muscle stiffness and delayed relaxation after exercise. Genetic testing reveals a mutation affecting the sarcoplasmic reticulum Ca²⁺‑ATPase (SERCA) pump, which is responsible for actively transporting calcium ions back into the sarcoplasmic reticulum after a contraction. As a result, calcium remains in the cytosol longer than normal, delaying the muscle’s return to its resting state. Based on this scenario, which phase of the muscle twitch is most likely to be prolonged in this athlete?
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