Bicep weakness

Hi, my left bicep started getting weaker about 3 weeks ago. Last week, after a workout, it felt weaker than ever. I could barely pick up anything. There's no pain in my bicep, it just feels very weak. I can't curl anything moderately heavy. I have stopped weightlifting for the past week. My bicep has got a little better, and has gained a little bit more strength, but is still very weak compared to my original strength. Just a reminder, there is no pain. What could be wrong with it, and how long till I regain my strength in my bicep?

[DavidKarthus]

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